#66964: Opioid Use Disorder

Long-term use of prescription opioids for chronic pain results in abuse or dependence in 2.8% to 18.9% of patients [29]. Predictors of dependence on opioid medications among pain patients include substance abuse-related diagnoses, positive toxicology for opioids, and other medical diagnoses, including diagnosis of comorbid psychiatric conditions [33]. Other patients at risk include those with idiopathic pain (no clear etiology) or high levels of psychologic distress or disability [7]. Alcoholism and other drug dependence are often viewed as contraindications for opioid medications in chronic noncancer pain.

The number of overdose deaths involving synthetic opioids in 2021 was almost 23 times the number of such deaths in 2013. Death rates from synthetic opioids increased more than 22% from 2020 to 2021 and accounted for almost 88% of all opioid-related deaths in 2021 [35,36]. Age-adjusted rates of overdose deaths from synthetic opioids increased significantly from 2001 through 2021, with different rates of change over time [36]. Rates of drug overdose deaths involving synthetic opioids increased from 17.8 per 100,000 population in 2020 to 21.8 per 100,000 population in 2021 [37]. Increases in overdose deaths from synthetic opioids are being driven by increases in fentanyl-involved overdose deaths from nonpharmaceutical fentanyl [36]. From 2018 to 2019, a total of 20 states experienced relative increases in death rates from synthetic opioids, with the highest rate in 2019 in Delaware (38.4). The largest relative rate increase occurred in Colorado (95.5%), and the largest absolute rate increase occurred in the District of Columbia (7.6). No state experienced a significant decrease [38].

The opioid overdose rate among women has increased faster than it has in men. From 1999 to 2015, overdose fatality increased 471% in women, compared with 218% for men. There has been an alarming increase in the rates of synthetic opioid-related deaths, which increased 850% in women between 1999 and 2015 [39]. In aggregate, women tend to possess background characteristics and opioid analgesic use patterns that may contribute to overdose vulnerability. Women are more likely to experience chronic pain, receive prescriptions for opioid analgesics, receive higher doses of opioids, and use opioids for longer periods than men. Substance use disorders involving opioid analgesics are thought to develop more rapidly in women, and women may be more likely to obtain opioid prescriptions from multiple prescribers than men [40].

Fentanyl Contamination of Other Drugs

Fentanyl and fentanyl analogs are being increasingly mixed into counterfeit opioids, heroin, and other drugs. This contamination of other drugs is a growing concern as it can lead to an increase in overdose deaths in unsuspecting opioid users as well as among individuals who are opioid naïve [36]. A 10-state study (Kentucky, Maine, Massachusetts, New Hampshire, New Mexico, Ohio, Oklahoma, Rhode Island, West Virginia, and Wisconsin) found that nearly 57% of people who died from a drug overdose tested positive for fentanyl and fentanyl analogs as well as cocaine, methamphetamine, or heroin. Ohio reported the largest numbers and most substantial increases in deaths with any fentanyl analog detected [41]. Among the overdose deaths with fentanyl analogs detected, the analogs were determined by either medical examiners or coroners to have contributed to the death in more than 95% of cases [41]. The most potent fentanyl analog that has been detected in the United States is carfentanil, and it is responsible for the largest number of deaths involving fentanyl analogs. Among 11,045 opioid overdose deaths in 10 states from July 2016 to June 2017, more than 20% tested positive for any fentanyl analog and more than 11% tested positive for carfentanil [42].

Overdose death rates involving heroin decreased by nearly 32% from 2020 to 2021 in the United States. However, in 2021 more than 9,000 people died from a heroin overdose, a rate of nearly three deaths for every 100,000 Americans. The number of heroin-involved overdose deaths in 2021 was three times the number in 2010, and more than 11% of all opioid deaths involved heroin [36].

Identified risk factors for fatal heroin overdose include male gender, single status, unemployment, history of heroin dependence, no current treatment for heroin dependence, intravenous (IV) use, and concomitant use of alcohol or benzodiazepines. An unexplained and consistent finding is that victims of fatal heroin overdose are generally older, experienced users. Also, at autopsy, a large proportion of overdose fatalities have relatively low blood morphine concentrations [34]. (Heroin is rapidly metabolized into morphine once administered.) Demographic patterns among overdose fatalities suggest that polydrug use and loss of tolerance are key factors, which partially explains low blood opioid concentrations. However, this does not explain the strong association of fatal overdose with age [34].

Risk factors for prescription opioid overdose are similar to those for heroin overdose, but also include obtaining overlapping prescriptions from multiple providers/pharmacies, taking high daily doses of prescription pain relievers, self-medication, polypharmacy, living in a rural area, and mental illness [43]. Most people who abuse prescription opioids get them free from a friend or relative. However, those at highest risk of overdose (i.e., those who use the drugs nonmedically 200 or more days per year) obtain them differently. More than 42% of those at highest risk of overdose obtain opioids using their own prescriptions; 33.9% obtain them from friends or relatives for free; 7.3% purchase the drugs from friends or relatives; and 7.9% purchase them from a drug dealer [12]. Individuals at highest risk of overdose are four times more likely than the average user to buy the drugs from a dealer or other stranger [44].

Historically, methadone was used primarily as pharmacotherapy for heroin addiction. During the 1990s, however, methadone gained increased acceptance for use as an analgesic, and methadone began to be prescribed to outpatients with moderate-to-severe noncancer pain. Prescribing rates soared over the next decade; comparison of methadone sales quantity between 1997 and 2007 shows an increase of 1,293% [45,46]. This rising use of methadone occurred simultaneously with concerns over the abuse potential of other opioids and the search for a relatively inexpensive long-acting opioid analgesic alternative [47].

Since the mid-2000s, methadone has become disproportionately represented in cases of opioid analgesic fatality. Based on data showing that 70% of fatalities among those prescribed methadone occurred in the first seven days of treatment, the FDA changed the methadone labeling in 2006 to lengthen dosing intervals from every 3 to 4 hours to every 8 to 12 hours; the initial recommended dose of 2.5–10 mg was unchanged [48]. In 2008, use of the highest oral dose (40 mg) preparations was prohibited from use in pain treatment and restricted to addiction therapy [49].

In addition to the general risk factors for opioid overdose, specific factors that contribute to methadone fatality include [49]:

Heroin, or diacetylmorphine, is a highly potent, semisynthetic analgesic produced by the anhydrous acetylation of morphine. Heroin is generally believed to have no significant opioid receptor activity; however, heroin is rapidly metabolized to 6-monoacetylmorphine (6-MAM) and then to morphine. While diacetylmorphine and 6-monoacetylmorphine readily cross the blood-brain barrier, morphine itself is much slower to do so; thus, heroin can be considered a prodrug that facilitates the brain entry of morphine [51]. The drug rapidly enters the brain after IV administration, where it binds to mu, kappa, and other stereospecific opioid-receptor binding sites in the locus coeruleus [8]. The onset of euphorigenic action is approximately 30 minutes after intranasal ingestion, 15 minutes after subcutaneous injection, and almost instantaneously after IV injection, with a duration of about three to four hours [8]. As with many other opioids, heroin reduces the anticipatory anxiety associated with emotional or physical pain and alters the perception of pain [8].

Heroin is rapidly deacetylated in the microsomes of the endoplasmic reticulum in the liver to 6-MAM, which is further deacetylated to morphine. It is excreted in the urine over a 30- to 40-hour period as free morphine and morphine 3-glucuronide [8]. Other drugs, including tricyclic antidepressants (TCAs), can inhibit the metabolism of heroin. Genetic variation in the expression of the enzymes involved in opioid metabolism and the potential for drug interactions at these sites may contribute to variation in response to heroin administration both among various individuals and within one individual [51].

The sought-after effects of heroin include intense tranquility, euphoria, analgesia, and a clouding of the sensorium, with the state of ecstasy and contentment immediately following IV injection being the most desired. Many novice heroin users experience adverse effects, such as mild nausea and vomiting. However, tolerance to these effects is soon achieved [8].

The lifestyle of the heroin addict seriously decreases life expectancy. Age-adjusted mortality rates have been found to be least seven times greater than that of the general population, adjusting for age, with death usually attributable to violence or drug effects. Also, the desire to replicate the most intense rush may compel the heroin addict to escalate the dose, resulting in acute heroin overdoses [8].

Codeine is approximately 60% as effective orally versus parenterally as an analgesic and respiratory depressant. Several codeine analogs, such as levorphanol, oxycodone, and methadone, have a high ratio of oral-to-parenteral potency, with the greater oral bioavailability reflecting lower hepatic first-pass metabolism [9].

Approximately 10% of ingested codeine is O-demethylated to morphine. Free and conjugated morphine can be found in the urine after therapeutic doses of codeine. Codeine has an exceptionally low affinity for opioid receptors, and the analgesic effect of codeine is due to its conversion to morphine. However, the antitussive effects of this drug may involve distinct receptors that bind codeine itself. The plasma half-life of codeine is two to four hours [9].

Codeine and promethazine syrup is the active component of the recreational drug "purple drank;" other common names include "syrup" and "lean" [54]. The combination of the purple antitussive, soft drinks, and in some cases candy has been mentioned in hip-hop music since the late 1990s and has been particularly popular in the South [54]. All opioid/soft drink concoctions may colloquially be referred to as "sizzurp."

Tramadol is a synthetic codeine analog and a weak mu-opioid receptor agonist. Tramadol is unusual among opioids in that a portion of its analgesic effect is produced by norepinephrine and serotonin uptake inhibition [9]. Tramadol is as effective as morphine or meperidine in the treatment of mild-to-moderate pain. It is 68% bioavailable following a single oral dose and 100% available following intramuscular administration. The affinity of tramadol for the mu-opioid receptor is only 1/6,000th that of morphine. However, the primary O-demethylated metabolite of tramadol is two to four times as potent as the parent drug and may partially explain the analgesic effect. Physical dependence with tramadol has been reported [9].

Levorphanol (brand name Levo-Dromoran) is the only commercially available opioid agonist of the morphinan series, and it possesses pharmacologic effects very similar to those of morphine. Levorphanol is metabolized less rapidly than morphine and has a half-life of 12 to 16 hours [9,55].

Meperidine is predominantly a mu-receptor agonist. This agent, available under the brand name Demerol, is no longer recommended for treatment of chronic pain due to concerns of metabolic toxicity. Meperidine should not be used for longer than 48 hours or in doses greater than 600 mg/day [55]. The central nervous system effects are similar but not identical to that of morphine. In equianalgesic doses, meperidine produces comparable sedation, respiratory depression, and euphoria as morphine. Some patients may experience dysphoria. Meperidine can cause central nervous system excitation, characterized by tremors, muscle twitches, and seizures, primarily due to accumulation of the metabolite normeperidine [1]. Large doses repeated at short intervals by addicts who have developed a tolerance to the sedative effects can produce an excitatory syndrome characterized by hallucinations, tremors, muscle twitches, dilated pupils, hyperactive reflexes, and convulsions [9]. Meperidine is primarily abused by healthcare professionals [9].

Diphenoxylate (in combination with atropine as Lomotil) and loperamide (Imodium) are meperidine congeners that are approved by the U.S. Food and Drug Administration (FDA) for the treatment of diarrhea [55]. These drugs slow gastrointestinal motility by affecting the circular and longitudinal muscles of the intestine, presumably through interaction with opioid receptors in the intestine [9].

Fentanyl is a synthetic opioid related to the phenylpiperidines. The actions of fentanyl and its congeners (sufentanil, remifentanil, and alfentanil) are similar to those of other mu-receptor agonists. Fentanyl is a popular drug in anesthesia practice because of its relatively short time to peak analgesic effect, rapid termination of effect after small bolus doses, and relative cardiovascular stability. Fentanyl is approximately 100 times more potent than morphine, and sufentanil is approximately 10 times more potent than fentanyl. These drugs are usually administered intravenously and are substantially more lipophilic than morphine. Time to peak analgesia is rapid, usually within five minutes. Respiratory depression potential is similar to other mu-receptor agonists with a more rapid onset. Fentanyl and sufentanil treatment of chronic pain has become more widespread, and transdermal patches that provide sustained release for 48 hours or more are available [9].

Fentanyl is delivered via the transdermal route for up to 72 hours, with patches containing 2.5, 5, 7.5, or 10 mg of fentanyl. Abuse of both the injectable formulation of fentanyl (Sublimaze) and the transdermal patch is primarily, but not exclusively, a problem among healthcare professionals due to availability and proximity. Fentanyl may be extracted from the patch and injected, or the patch contents may be chewed, ingested, or inhaled. Even a patch that has been used for three days contains sufficient fentanyl to be abused [1].

Methadone was first synthesized as an analgesic in Germany during World War II as a response to the difficulty in obtaining raw opium [56]. Methadone is a long-acting mu-receptor agonist with pharmacologic properties quantitatively similar to those of morphine [9]. Methadone is well-absorbed from the gastrointestinal tract and can be detected in plasma within 30 minutes of oral ingestion. Peak concentrations occur in the brain within one or two hours of subcutaneous or intramuscular administration [9]. Oral bioavailability approaches 100% [55,56].

In contrast to heroin, the activity of methadone is due almost exclusively to the parent drug rather than its metabolites. The drug is characterized by a long, but highly variable, half-life. One of the primary elimination pathways of methadone is N-demethylation, with cytochrome P450 3A4 (CYP 3A4) the major enzyme involved [55]. Inhibition of CYP 3A4 with drugs such as ketoconazole and erythromycin may enhance and prolong the effect of methadone. Its induction with drugs such as rifampin, carbamazepine, and phenytoin will have the opposite effect [51,55]. Liver disease can increase the half-life of methadone, but renal failure will not [56]. Additionally, CYP 2D6 may be involved in the metabolism of the active enantiomer of methadone; less than 7% of white persons and more than 25% of Ethiopian persons are ultrarapid metabolizers at CYP 2D6. Individuals with this polymorphism may be more likely to experience methadone overdose [51,57].

Following absorption, methadone is distributed to the brain, liver, kidneys, muscles, and lungs. Tissue binding predominates over binding to plasma proteins, and accumulation of the drug occurs in these tissues with repeated dosing. Plasma concentrations are maintained by this peripheral reservoir. Methadone reabsorption from the tissues may continue for weeks after administration has ceased. It has an elimination half-life of about 22 hours, but metabolism varies in each person [58].

One of the most significant advantages of methadone is that it alleviates cravings for opioids (a primary reason for relapse) and blocks many of the pleasurable effects of heroin, which helps reinforce abstinence [56]. Some of the characteristic properties of methadone are its analgesic activity, its efficacy by the oral route, its extended duration of action in suppressing withdrawal symptoms in physically dependent individuals, and its ability to demonstrate persistent effects with repeated administration [9]. Accidental overdose fatalities can occur when pain patients re-administer methadone when the analgesia wears off and pain returns, potentially elevating plasma concentrations to life-threatening levels. These same pharmacologic properties also imperil those who use it illicitly. Opioid abusers often co-administer benzodiazepines, which greatly elevates lethality risk with methadone. Concurrent use of alcohol poses the same risk [47].

In methadone clinics, methadone is usually dispensed in prepared individual doses mixed with fruit juice to discourage IV use. Methadone is also prescribed for pain. Until recently, there had been little evidence that diversion of methadone from pain management was occurring on any substantial scale. The majority of diverted methadone is used by heroin addicts to self-medicate symptoms of opioid withdrawal. To date, there is no evidence that diversion of methadone from methadone clinics has resulted in significant numbers of new opioid addicts [59].

More frequent adverse effects associated with methadone use include sweating, decreased libido, weight gain, constipation, and irregular menstrual periods, all occurring primarily during the initial stabilization process. Uncommon side effects include facial flushing, pruritus, euphoria or dysphoria, insomnia, urinary retention, and bradycardia [55]. Rarely observed side effects include biliary spasm, urticaria, syncope, overdose death, and torsades de pointes [56]. These effects are more common at higher doses and when methadone is combined with certain other drugs [60]. Risk of QTc prolongation and arrhythmia led to a 2006 black box warning [55].

Tolerance to the opioid properties of methadone develops within four weeks. The minimal effective dose is regarded as 40 mg, but some patients require much greater doses [55,56]. Subcutaneous administration of 10-20 mg methadone to former opioid addicts unambiguously produces euphoria similar in duration and magnitude to that of morphine. Methadone's overall abuse potential is comparable to that of morphine [9].

Hydrocodone is a semi-synthetic codeine derivative first used clinically as an antitussive and analgesic in the 1920s. Following a 10-mg oral dose, maximum serum level is observed in 1.3 hours [61]. Hydrocodone exhibits a complex pattern of metabolism, including O-demethylation, N-demethylation, and 6-keto reduction to the corresponding 6-a- and 6-b-hydroxymetabolites. The 2D6 enzyme demethylates hydrocodone at the 3-carbon position into hydromorphone, which has much stronger mu binding than hydrocodone. Similar to codeine, it has been proposed that hydrocodone is a prodrug. Its analgesic properties are generally considered equipotent to codeine [62].

Oxycodone is similar in structure to hydrocodone, with the addition of a hydroxyl group at the 14-carbon. Oxycodone, as a hydrochloride salt, is a pure agonist opioid that has been in clinical use since 1917. Unlike codeine and hydrocodone, oxycodone is a potent analgesic in its own right and not a prodrug, although 2D6 activity creates the active opioid analgesic metabolite oxymorphone (synthesized and marketed as the analgesic Opana). Oxycodone is suitable for oral administration due to high bioavailability (60%) but may also be taken intramuscularly, intravenously, subcutaneously, or rectally; however, oxycodone is only commercially available in oral preparations [55]. In terms of analgesic potency and lipophilicity, oxycodone is comparable to morphine, and both drugs possess similar abuse potential. With the exception of hallucinations, which occur more rarely with oxycodone than with morphine, the side effects of these drugs are highly similar [63].

Oxycodone is metabolized by demethylation to noroxycodone and oxymorphone followed by glucuronidation [55]. A urine screen may reveal oxycodone alone, oxycodone and oxymorphone, or oxymorphone alone [64].

Since 1995, oxycodone has been marketed in the United States as OxyContin, a Schedule II controlled-release oral tablet formulation. Oxycodone is also available in immediate-release tablets in combination with aspirin or acetaminophen under various trade names, including Percodan and Percocet, which contain 2.5–10 mg of oxycodone [55]. The oxycodone content of OxyContin ranges from 10 mg to 80 mg. When taken orally, OxyContin tablets release oxycodone over a 12-hour period. However, when the controlled-release mechanism is destroyed by crushing the tablet, the oxycodone can be snorted, ingested, or injected. It is this delivery of a large amount of the active drug in a relatively brief time period (compared to the intact tablet and the low-dose immediate-release form) that underlies addicts' interest in OxyContin [1].

In 2014, the FDA approved an extended-release version of oxycodone that is formulated to include naloxone in order to deter misuse [65]. If crushed and snorted or crushed, dissolved, and injected, the naloxone will block the euphoric effects of oxycodone, potentially deterring this type of abuse. This combination drug is intended for patients for whom alternative treatment options for chronic pain are ineffective or not tolerated [65]. The drug is no longer available in the United States [55].

Hydromorphone is a semi-synthetic hydrogenated ketone of morphine and shares the pharmacologic properties typical of mu-opioid agonists. Hydromorphone is a more potent analgesic than morphine; on a milligram basis, hydromorphone is 5 times as potent orally and 8.5 times as potent intravenously. Hydromorphone can be administered by infusion, intramuscularly, orally, or rectally [66].

Following oral administration of conventional-release hydromorphone, the drug is rapidly absorbed and undergoes hepatic first-pass elimination of approximately 50%. The terminal elimination half-life after IV administration is 2.5 to 3 hours. The primary mode of elimination is by urinary excretion as hydromorphone-3-glucuronide, the primary metabolite. Some metabolites may have greater analgesic activity than hydromorphone itself but are unlikely to contribute to the pharmacologic activity. Side effects are comparable to morphine [66].

In 2023, the FDA issued a drug safety communication to update the prescribing information for immediate-release (IR) and extended-release (ER)/long-acting (LA) opioid analgesics. The safety communication includes updates to boxed warnings, indications and usage, dosage and administration, warnings and precautions, and the medication guide [67]. Revised labels must state that [67]:

Pentazocine was developed in an effort to synthesize an effective analgesic with little or no abuse potential. With agonistic actions and weak opioid antagonistic activity, the pattern of central nervous system effects is similar to that of morphine-like opioids, including analgesia, sedation, and respiratory depression. Dysphoric and psychotomimetic effects can be precipitated by higher doses (60 to 90 mg) [9].

In the 1970s and early 1980s, pentazocine (Talwin) was combined with the crushed, blue-colored antihistamine tablet tripelennamine and used intravenously, known as "Ts and Blues." Factors contributing to its widespread abuse included placement outside Schedule II and the erroneous belief that the drug was not abusable. Pentazocine was also widely abused by physicians because it could be prescribed in large quantities outside the stringent Schedule II monitoring system. At one point, pentazocine abuse became so prevalent that the manufacturer contemplated removing the drug from the market. Pentazocine was ultimately reformulated by the inclusion of the opioid antagonist naloxone. Similar to buprenorphine formulations containing naltrexone, when this formulation is taken as directed, the user experiences only the pentazocine effect because of poor oral naloxone absorption. However, if the tablet is dissolved and injected, the naloxone blocks the opioid effects of the pentazocine and precipitates acute opioid withdrawal [1].

Nalbuphine is an agonist-antagonist opioid related to naloxone and oxymorphone, with a spectrum of effects that qualitatively resembles that of pentazocine but with a lower potential to produce dysphoric side effects. Although doses of 10 mg or less produce few side effects, much higher doses (70 mg) can produce psychotomimetic side effects such as dysphoria, racing thoughts, and distorted body image. Prolonged administration of nalbuphine can produce physical dependence and withdrawal [9].

Butorphanol is a morphinan congener with a profile of actions similar to those of pentazocine. It is generally more suitable for the relief of acute pain than chronic pain. Major side effects include drowsiness, weakness, sweating, feelings of floating, and nausea. Although the incidence of psychotomimetic side effects is lower than that with equianalgesic doses of pentazocine, they are qualitatively similar. Physical dependence to butorphanol can develop from regular use [9,55].

Buprenorphine was initially suggested in 1978 as an alternative oral opioid substitution therapy for opioid addicts. Buprenorphine and methadone are the two most widely used and effective pharmacotherapies for opioid use disorder, and both have regulatory approval in the United States for this indication [68]. Buprenorphine is a semi-synthetic opioid derivative made from thebaine, one of the naturally occurring alkaloids in opium [69]. Buprenorphine, sold as Buprenex, Subutex, Belbuca, or Sublocade, is a long-acting partial opioid agonist that is classified as a Schedule III narcotic, in contrast to methadone and LAAM, which are Schedule II [55,56,70].

Buprenorphine has a very low oral bioavailability due to substantial intestinal and hepatic metabolism. The sublingual formulation used to treat opioid dependence is well-absorbed and produces opioid agonistic effects comparable to subcutaneous administration. Maximum plasma level is achieved 70 to 90 minutes after sublingual administration, and absolute bioavailability is 35% to 50% [69]. Following absorption, buprenorphine initially accumulates in the liver, kidneys, muscular tissue, and fatty tissue. It is released from fatty tissue when the plasma level drops and is then available at the opioid receptor. The slow dissociation kinetics explains the prolonged period of effectiveness. Buprenorphine is metabolized through the hepatic cytochrome P450 pathway. Approximately 80% is eliminated through binary excretion of the glucuronidated metabolites and 20% via the urinary route [69].

The minimum daily dose needed to suppress opioid use is about 4 mg. Larger doses of buprenorphine (32 mg) result less in an increase in therapeutic effect but more in an extension of the effect, which can last for up to 48 hours [69].

In 2014, the FDA approved a buccal film containing both buprenorphine and naloxone [71]. This combination therapy is applied once daily to suppress signs and symptoms of opioid withdrawal [55]. In 2016, the FDA approved the first buprenorphine implant (Probuphine) for opioid dependence [72]. The implant provides a constant, low-level dose of buprenorphine for six months. It is designed for use in patients who are already stable on a low dose of other forms of buprenorphine, as part of a complete treatment program. Because Probuphine must be inserted and removed surgically, healthcare providers are required to complete training and certification through the Probuphine Risk Evaluation and Mitigation Strategy (REMS) program [72]. In 2017, the FDA approved a once-monthly subcutaneous injection (Sublocade) for opioid use disorder [73]. Sublocade is intended for use in adult patients with moderate-to-severe opioid use disorder who have been on a stable dose of buprenorphine treatment for a minimum of seven days. The drug must be administered in a healthcare setting to avoid inadvertent IV administration that could result in death [73]. In 2023, the FDA approved buprenorphine extended-release (Brixadi) for subcutaneous injection [74]. Brixadi is approved in both weekly and monthly subcutaneous injectable formulations at varying doses, including lower doses that may be appropriate for those who do not tolerate higher doses of extended-release buprenorphine that are currently available. The weekly doses are 8, 16, 24, and 32 mg; the monthly doses are 64, 96, and 128 mg [74]. Buprenorphine use is contraindicated for patients with alcohol intoxication, delirium tremens, and treatment with monoamine oxidase inhibitors. Cases of lethal buprenorphine intoxication almost always involve polyintoxication [69]. Buprenorphine contains a black box warning regarding the potential for serious, life-threatening, or fatal respiratory depression, especially during initiation or dose escalation [55]. Upon discontinuation, a withdrawal syndrome develops, with a delayed emergence in two days to two weeks. Signs and symptoms of buprenorphine withdrawal are typical of a milder morphine-type withdrawal and last roughly one to two weeks [9]. The more benign withdrawal syndrome is due to its partial agonist property at the mu receptor and weak antagonist property at the kappa receptor [56]. Section 1262 of the Consolidated Appropriations Act of 2023 removes the federal requirement for practitioners to apply for a special waiver prior to prescribing buprenorphine for the treatment of OUD. It also removes other federal requirements association with the waiver, such as patient limits. Separately, section 1263 of the Act requires new or renewing DEA registrants to meet one of three requirements (i.e., training, certification, or education). This section became effective June 27, 2023. Additional information is available on the SAMHSA website at https://www.samhsa.gov/medications-substance-use-disorders/waiver-elimination-mat-act [75,76].

The diverse biologic effects of opioids are manifested through specific opioid receptors distributed throughout the central and peripheral nervous system. Opioid receptors, upon the binding of opioid drugs (or endogenous opioid peptides), regulate a multitude of intracellular signaling pathways. Involvement of opioid receptors in opioid dependence is unequivocal. This is reliably demonstrated by the rapid precipitation of withdrawal syndromes in opioid addicts by opioid receptor antagonists such as naloxone [83].

Repeated exposure to short-acting opioids can result in durable alterations in opioid receptor kinetics, transmembrane signaling, and postreceptor signal transduction [84]. Opioid dependence requires sustained activation of opioid receptors, and this chronic signaling process ultimately leads to changes in protein functions of gene transcription [83].

Opioid receptors are members of the G-protein receptor family, and each opioid receptor uses inhibitory G-proteins for signal transduction. Opioid receptors have the capacity to interact with five different forms of G-proteins, regulating a diverse spectrum of effectors ranging from adenylyl cyclases and ion channels to mitogen-activated protein kinases. These isoform-specific and differential regulations of various classes of effectors are combined into a sophisticated signaling network that mediates opioid actions. The enormous diversity in opioid signaling stems from the array of effectors and signaling molecules that functionally interact with the G-protein beta gamma complex [83].

Prolonged administration of opioids causes molecular and cellular adaptations that rapidly develop into tolerance and dependence. An upregulation of adenylyl cyclase responsiveness, referred to as adenylyl cyclases superactivation, is a classic sign of this tissue adaptation [83].

G-protein signals lead to changes in gene expression, and opioid-induced, long-term functional alterations of the nervous system involve changes in gene expression. Many opioid-induced signals converge at the level of transcription factors, although little is known about the exact mechanisms of gene transcription in the development of opioid tolerance and dependence [83].

Drugs with an abuse liability have habit-forming actions that can be localized in a variety of brain regions. Drugs of abuse mimic or enhance the actions of endogenous chemical messengers in the brain [85]. The mesolimbic dopamine system is the likely substrate upon which opioids act to produce their reinforcing effects. Both the positive (rewarding) and negative (aversive) reinforcement of opioid mu- and kappa-receptor agonists are mediated by the mesolimbic dopamine system [81].

Opioids produce reinforcement by inhibition of the GABA neurons that normally inhibit dopaminergic neurons in the ventral tegmental area. This results in a surge of dopamine in the nucleus accumbens and other mesolimbic-mesocortical brain regions [86]. The neurochemical cascade begins with activation of mu- or kappa-opioid receptors differentially distributed on GABAergic cells in the ventral tegmental area and nucleus accumbens and dopamine terminals in the nucleus accumbens. This activation produces rewarding and aversive effects by increasing or decreasing dopamine release in the nucleus accumbens. Inhibition of medium spiny GABAergic neurons in the nucleus accumbens by dopamine and opioids can synergistically facilitate opioid reinforcement. Increases in glutamatergic afferents into the ventral tegmental area may facilitate opioid reinforcement by activating dopamine neurons. An increase in glutamate activity in the nucleus accumbens may decrease opioid action by activating nucleus accumbens GABAergic cells. Also, an increase in nucleus accumbens 5-HT by opioids modulates opioid reinforcement by activation of 5-HT1 and/or 5-HT3 receptors [81].

Opioid use has been implicated in gonadal dysfunction [92]. Central hypogonadism can result from opioid receptor activation in the vicinity of the hypothalamus. Resultant diminished secretion of gonadotropin-releasing hormone can lead to decreases in gonadotropin and testosterone levels. This effect may decrease over time secondary to the development of tolerance [91].

Heroin use has been associated with abnormalities in glucose metabolism by multiple mechanisms. Fasting insulin levels can be substantially higher in heroin addicts than in control subjects, and insulin resistance stemming from opioid use may be coupled with beta cell dysfunction [93]. Heroin addicts often have lower acute insulin response than control patients evaluated by oral glucose tests and response to a standard meal. This blunted glucose response suggests an association between opioid use and abnormal glucose metabolism [91]. The use of highly active anti-retroviral therapy (HAART) for the treatment of HIV infection is also associated with a number of metabolic problems, including increased prevalence of insulin resistance, dyslipidemia, and changes in fat distribution. Because opioid use can also result in metabolic abnormalities, the presentation of patients who are both HIV-positive and opioid dependent may be complicated.

Chronic heroin use may also complicate dyslipidemia, evidenced by elevated total cholesterol levels, hypertriglyceridemia, decreased total cholesterol and high-density lipoprotein, and elevated triglyceride levels relative to controls [91].

Opioid addicts may also have impaired adrenal function, documented by a high prevalence of adrenal insufficiency and abnormal response to the cosyntropin test [92]. The action of heroin on neurotransmitters that regulate the secretion of corticotrophin-releasing factor, leading to disturbances in cortisol levels, has been hypothesized as the underlying pathophysiology. This is supported by the observation of lower plasma cortisol levels concurrent with depressed ACTH levels in heroin addicts [91].

In addition, chronic opioid use may contribute to low bone mineral density through reduction in lumbar bone mineral density. Growth hormone axis abnormalities are also seen in heroin addicts [91].

While under the influence of acute opioid ingestion, the ability to work safely or drive a car can be impaired. This does not appear to be the case with methadone patients who have adapted to the effects of opioids for months or even years, a reflection of the substantial tolerance to the central depressing effect when opioids are taken regularly on a long-term basis [96].

A review of the cognitive functioning of methadone patients found that [96]:

Researchers concluded that among methadone-maintained patients without complicating comorbidity, visual structuring and reaction are not impaired [96]. Performance of attention, visual orientation, and eye-hand coordination are worsened. In general, performance of methadone patients and comparable healthy subjects overlap to a substantial degree. The study results may be better explained by sociodemographic factors than by the grouping factor; age, gender, and educational attainment showed a greater influence than methadone use. The authors concluded that being a methadone patient does not necessarily mean that impairment of cognitive-motor skills performance is inevitable [96]. Authors of more recent studies have reported similar findings [97,98].

The practical application of these findings suggests that methadone-maintained patients may be as capable as healthy persons in job performance. If job demands encompass skills with no differences found between healthy subjects and methadone patients, if minimum prerequisites are not extraordinarily high, or if patients exhibit favorable features exclusive of their methadone dependence, job performance is unlikely to be affected [96].

Variation has been found in the acquisition of tolerance to different opioid effects, including respiratory depression [34]. The role of tolerance in heroin overdose is suggested by the rigors of the heroin lifestyle, which often results in a reduction in use after a decade or more of use. Often, heroin addicts increase the use of other drugs, such as alcohol, to compensate for reduced heroin use. Both of these factors increase the risk for overdose.

Polysubstance use in cases of fatal heroin overdose is so frequent that polydrug toxicity is often a better description of the cause of death. The primary drugs associated with fatal and nonfatal overdose are alcohol, benzodiazepines, and TCAs. The risk of nonfatal heroin overdose is increased significantly by TCA use but not by selective serotonin reuptake inhibitor (SSRI) use [16].

Alcohol and benzodiazepines are relatively weak respiratory depressants but can act synergistically with opioid agonists to produce substantial respiratory depression. Stimulants act as functional or physiologic opioid antagonists and may therefore minimize the respiratory depressant effects of opioids [51].

Reducing the risk for harm involves education on polydrug use and needle-exchange programs [99]. The authors of one review noted that there was positive evidence, though limited, to support education regarding noninjecting routes of administration, brief interventions, and supervised injecting facilities [127]. Given that a harm-reduction approach can address risk behaviors that may occur alongside drug use, the authors of one paper suggest that risk-reduction education be based on harm reduction philosophy as a whole rather than on the specific harms of drug use and harm reduction strategies (e.g., needle-exchange programs) [128]. The authors defined six principles—humanism, pragmatism, individualism, autonomy, incrementalism, and accountability without termination—and generalized them for use in healthcare settings with patients beyond those who use illicit substances. Each principle was defined and providers were given descriptions of how to deliver interventions informed by the principles as well as examples of how to apply each principle in the healthcare setting [128].

To improve response to overdoses, opioid abusers and their friends and families should be taught simple cardiopulmonary resuscitation skills to keep comatose users alive until emergency medical personnel arrive. Associates of users should be encouraged to call an ambulance when overdose occurs. The provision of naloxone to opioid users should be tested and evaluated; naloxone could be distributed through existing outlets, such as needle and syringe exchanges, pharmacies, urgent care facilities, or treatment agencies. Heroin users should also be encouraged to switch to noninjecting routes of administration to reduce related morbidity and mortality [99].

Needle-exchange programs, also referred to as syringe services programs, have been shown to be effective in reducing drug-related health problems, reducing injection frequency, and increasing entry and retention in drug treatment [77]. According to one review, there is sufficient evidence of efficacy, effectiveness, and financial benefit to recommend needle-exchange and outreach programs [127]. It is important to note that information regarding infection prevention strategies be provided to all participants in needle-exchange programs, as increased incidences of HIV and other bloodborne pathogens have been noted in this population [129]. The Consolidated Appropriations Act of 2016 gives states and local communities, under limited circumstances, the opportunity to use federal funds to support certain components of needle-exchange programs. Although federal funds cannot be used to purchase sterile needles or syringes for illegal drug injection, these funds can be used to support a comprehensive set of services as part of a needle-exchange program [130].

Medically supervised injecting rooms, or overdose prevention centers (OPCs), are officially designated areas where injecting opioid users, often persons who use heroin, can inject without fear of arrest and with knowledge that medical assistance is available if overdose occurs. Such facilities have existed in Switzerland since 1986, in Germany since 1994, and in the Netherlands since 1996. The goal of OPCs is to promote health and reduce risk behaviors and public nuisance, with a specific focus on overdose reduction and hygiene [131]. Several descriptive studies have shown significant effects on harm reduction and reduction of public nuisance [77].

Heroin maintenance, also referred to as heroin-assisted treatment, is the implementation of heroin prescriptions under medical supervision. This option may improve health and reduce heroin overdoses, illicit opioid use, and crime. However, formidable barriers to heroin maintenance exist in the United States [99].

One systematic review compared heroin maintenance to methadone or other substitution treatments of opioid dependence for efficacy and acceptability; retaining patients in treatment; reducing the use of illicit substances; and improving health and social functioning [132]. Eight studies involving 2,007 patients met the inclusion criteria. Five studies compared supervised injected heroin plus flexible dosages of methadone to oral methadone alone. Results suggest an added value of heroin prescribed alongside flexible doses of methadone for long-term, treatment-refractory, opioid users to reduce use of illicit substances and sustain treatment [132].

Ultra-rapid opioid detoxification (UROD) has been developed as a means of avoiding the physical symptoms of withdrawal from opioids through the use of general anesthesia. UROD consists of naltrexone-assisted detoxification under heavy sedation or full anesthesia. Chemical sedation has been used since the early 1940s in the management of drug withdrawal. The major breakthrough in the management of opioid withdrawal occurred with the addition of an opioid antagonist during chemical sedation [142]. UROD was introduced in 1990 primarily by private practitioners in a for-profit setting [143].

Traditional withdrawal management utilizes the substitution of the short-acting opioid with a long-acting opioid and subsequent tapering or use of non-opioids. This may involve substantial discomfort to patients, who often terminate the detoxification process and return to opioid use. Some may not even attempt to quit due to fears of the discomfort of the withdrawal process. Thus, attempts have been made to induce and shorten opioid withdrawal through the use of UROD [143].

UROD is also referred to as rapid or anesthesia-assisted detoxification. One reason for the proliferation of terms is that the anesthesia-assisted procedure was commercially used and was submitted as a registered trademark or patent. Therefore, other researchers had to devise novel names for the process. Suggested classification is [143]:

The common underlying themes in all UROD techniques are a desire to condense the detoxification process into a shorter period to blunt the awareness of physical discomfort and to shorten the time lag between a patient's last dose of opioid and transfer to naltrexone maintenance [143]. This is accomplished by precipitating withdrawal following the administration of opioid antagonists under deep sedation or anesthesia.

A highly specific subgroup of patients may benefit more from UROD. This includes patients unable to abstain with methadone substitution despite adequate motivation, patients unable to stop methadone, and patients who are socially and occupationally active and cannot go through a lengthy detoxification. Patient preference is also an important variable [143].

Absolute contraindications include pregnancy; a history or clinical suspicion of cardiac disease; chronic renal impairment; liver disease; current dependence on benzodiazepines, alcohol, or stimulants; and history of psychotic illness [143]. Relative contraindications include a history of treatment for depression and unstable social circumstances. A comprehensive plan to stabilize such patients should be undertaken before the procedure [143]. Patients with chronic pain syndromes requiring opioid medication are not good candidates unless their pain can be controlled by alternative methods [80].

UROD is best performed in an intensive care unit with full resuscitative equipment and monitoring available [80]. Initiation of opioid withdrawal is precipitated by IV injection of a high-dose antagonist, usually naloxone. Antagonists are chosen that have high binding coefficients relative to agonists (naltrexone binds at the mu receptor 34 times more than morphine) [80]. Parameters that indicate adequacy of withdrawal include a 20% decrease of ventilation below the maximum minute ventilation, an electrocardiogram (ECG) detection of decreased QQ variability, and electroencephalogram (EEG) normalization [80].

Detoxification and withdrawal are rarely complete following UROD, and residual withdrawal symptoms can include drug craving, sympathetic hyperactivity, muscle pain, bone pain, nausea, vomiting, diarrhea, and insomnia. UROD does little to prevent protracted abstinence syndrome, which can last 3 to 10 weeks. Naltrexone may reduce opioid craving during the post-UROD period, with 50 mg per day recommended for relapse prevention [80]. However, patients undergoing long-term naltrexone therapy can become sensitized to opioid drugs, heightening the risk of fatal overdose if opioid use is resumed. Patients with a history of pre-existing liver dysfunction should undergo naltrexone maintenance therapy only under careful supervision. Clonidine may diminish sympathetic hyperactivity and should be continued through the protracted abstinence syndrome [80].

The withdrawal syndrome observed in many of the published studies on UROD was protracted, as reflected in the duration of inpatient stay, which varied from 24 hours to eight days, with a mean duration of three to four days. Therefore, alternatives to UROD are considered to be more cost-effective [143]. Krabbe et al. compared abstinence rates and withdrawal effects of UROD with standard methadone tapering in a prospective three-month trial [144]. They found significantly higher abstinence rates and fewer withdrawal symptoms in UROD patients versus methadone patients at one and two months, with no differences at three months.

A major shortcoming of UROD is the lack of evidence that an opioid antagonist can accelerate the restoration of neurobiologic homeostasis following opioid withdrawal [143]. Although significant drawbacks and questionable long-term efficacy exist with UROD, popular demand has proven difficult to restrain, in part due to the marketing of the procedure as a painless cure for opioid dependence. Marketing and the media have also blurred the fact that the original purpose of the procedure was to induce patients as rapidly as possible onto naltrexone and not to magically and permanently terminate years of opioid dependence [142]. There are a number of drawbacks to UROD relative to other detoxification methods. For example, one study found that, when used alone, naloxone has a high relapse rate in the long term [145]. The study included 64 opioid-dependent men 18 years of age and older (mean age: 31.1 years) at the time of UROD. One month after UROD, 48 patients (75%) reported relapse and 16 patients (25%) reported abstinence. There was no significant difference between the two groups regarding marital status, level of education, and family history of opioid dependence. Four patients from the nonrelapsed group reported on episode of opiate use [145]. Another study was conducted to assess UROD efficacy with naltrexone and estimate the relapse rate in a two-year follow-up period [146]. A total of 424 opioid-addicted self-reporting patients were enrolled in the study and entered the UROD program; 400 patients completed the program. Of the total patients, 303 (75.75%) were successful and 97 (24.25%) relapsed. No patients in the relapse group continued naltrexone maintenance at six-month follow-up. The relapse rate was 14% at the first month visit and 24% at the six-month visit and thereafter. All relapsed patients had discontinued use of naltrexone before relapse occurred [146]. A Canadian review of the evidence for UROD found no significant differences between UROD and control groups in commencement or duration of withdrawal treatment [147].

Serious adverse events related to the anesthetic procedure also have been reported. A randomized, controlled trial directly comparing naltrexone-assisted detoxification with and without full anesthesia clearly stated that heavy sedation or full anesthesia should not be used because it does not confer any advantages in withdrawal symptom severity or increased rates of initiation or maintenance and it increases the potential for life-threatening adverse events [77]. A trial comparing naltrexone-induced, anesthesia-assisted detoxification with buprenorphine- or clonidine-assisted detoxification found no difference in withdrawal severity and rates of completion. However, potentially life-threatening adverse events associated with the UROD anesthesia were observed. The authors concluded that the data do not support use of anesthesia for detoxification [148]. Heavy sedation compared to light sedation does not confer additional benefits in terms of less severe withdrawal or increased rates of initiation and retention on naltrexone maintenance treatment. The risk for adverse events, the high monetary cost, and use of scarce intensive care resources suggest that this form of treatment should not be pursued [149,150]. Additionally, UROD has not undergone the processes of therapeutic protocols, which are recognized as essential in scientific medicine, and no animal studies have been conducted with the procedure [142].

The goal of opioid replacement therapy is to reduce illicit drug use and associated health risks, with secondary goals of reducing unsafe sexual practices, improving vocational and psychosocial functioning, and enhancing quality of life [56]. The theoretical basis of opioid replacement stems from the finding that chronic opioid use results in an endogenous opioid deficiency as a result of the down-regulation of opioid production. This creates overwhelming cravings and necessitates interventions that shift the dependent patient's attention and drive from obsessive preoccupation with the next use of opioids to more adaptive areas of focus, such as work, relationships, and non-drug leisure activities [56].

The neurobiologic changes resulting from prolonged opioid exposure provide a rationale for specific pharmacotherapies, such as long-acting opioid agonists, that are aimed at stabilizing these complex systems [84]. Opioid agonist maintenance treatment stabilizes brain neurochemistry by replacing short-acting opioids, which can create rapid changes in opioid levels in the serum and brain, with a long-acting opioid that has relative steady-state pharmacokinetics. Opioid agonist maintenance treatment is designed to have minimal euphoric effect, block the euphoria associated with administration of exogenous opioids (competitive antagonism), eliminate the risk of infectious disease and health consequences associated with injection drug use, and prevent opioid withdrawal [84].

Successful maintenance treatment entails stabilization of opioid dependence through opioid receptor occupation. Positron emission tomography studies have revealed that only 25% to 35% of brain opioid receptors are occupied during steady-state methadone maintenance, suggesting that unoccupied opioid receptors disrupted during cycles of opioid abuse could normalize during methadone maintenance [56]. Additionally, opioid replacement therapy blocks much of the euphoria from illicit heroin use. Long-term opioid agonist treatment also has a positive impact on public health, through significantly reducing overdose deaths, criminal activity, and the spread of infectious disease [56].

As of 2020, 1,090,357 patients in the United States were enrolled in opioid replacement therapy in 1,754 opioid treatment programs [111]. However, this represents less than 20% of all opioid-dependent patients. Although some have criticized the practice of methadone and buprenorphine therapy on the grounds that one opioid is merely being substituted for another, the clinical benefits strongly support this treatment modality [56]. When compared to active street heroin users, these benefits include a four-times lower HIV seroprevalence rates, 70% fewer crime-days per year, and a one-year mortality rate of 1% (versus 8%) [60].

Methadone

The first demonstrated efficacy of methadone treatment for opioid dependence was published in 1965. Methadone is now the most inexpensive and empirically validated agent available for use in opioid replacement therapy. Studies have shown one-year treatment retention rates of 80%, with significant reductions in illicit opioid use [56]. Individual and group counseling are the main ancillary therapies and consist primarily of cognitive-behavioral and supportive-expressive approaches. There is some evidence that augmentation of methadone with intensive psychosocial therapy significantly improves outcomes [56]. Efforts to provide methadone in an office-based setting have been successful, although federal regulation has limited the flexibility of providers [84,107].

When considering initiation of methadone, the American Pain Society recommends that clinicians perform an individualized medical and behavioral risk evaluation to assess risks and benefits of methadone, given methadone's specific pharmacologic properties and adverse effect profile.

(https://www.jpain.org/article/S1526-5900(14)00522-7/fulltext Last Accessed: March 21, 2024)

Strength of Recommendation/Level of Evidence: Strong/low

As noted, methadone maintenance treatment offers substantial benefits over no treatment, including reduced risk of death and disease, reduced heroin use, reduced criminal involvement, and improved well-being. However, the benefits are less with poor-quality or under-funded programs. The quality of the staff-patient interaction, attitudes of staff, good management of clinics, and good record-keeping characterize higher-quality programs [153].

Methadone maintenance is also cost-effective [56]. A 1997 study of Veterans' Affairs patients showed that the estimated six-month costs are about $21,000 for an untreated drug abuser, $20,000 for an incarcerated drug abuser, and $1,750 for a patient enrolled in a methadone maintenance program [154]. A study using data from one healthcare plan reached a similar conclusion regarding cost-effectiveness (albeit with differing cost estimates) [155]. The annual costs (in 2004 dollars) were $18,694 for patients receiving no methadone with 0 or 1 outpatient addiction treatment visits; $14,157 for patients receiving no methadone with 2 or more visits; and $7,163 for patients receiving methadone.

There is an unrealistic expectation that opioid users should be able to stop using all drugs. Although some do successfully stop, dependence is a chronic problem for most patients, associated with frequent relapses, serious health risks, and psychosocial impairment [153]. Unfortunately, a serious stigma surrounds methadone treatment, which is experienced most acutely by patients but also by professionals. This may pose a barrier to treatment support [153].

Treatment is initiated with a dose of 25–30 mg and is gradually titrated in 5- to 10-mg increments per day to a desired range of 60–120 mg. Low-dose treatment is associated with less positive outcomes than doses of 60–120 mg/day or greater [55,60]. One published review of efficacy literature concluded that high doses of methadone (>50 mg daily) are more effective than low doses (<50 mg daily) in reducing illicit opioid use. This may be due to the increased availability of highly pure heroin [60]. Additionally, high doses of methadone are more effective than low doses of buprenorphine (<8 mg daily). High dosages of methadone are comparable to high dosages of buprenorphine (>8 mg daily) on measures of treatment retention and reduction of illicit opioid use [77]. Methadone is contraindicated for the following patients [55,107]:

Buprenorphine

Buprenorphine offers several advantages over methadone, including lower cost, milder withdrawal symptoms following abrupt cessation, lower risk of overdose, and longer duration of action, allowing alternate-day dosing [56,156]. Identifying subpopulations of opioid addicts who differentially respond to buprenorphine versus methadone has not been clearly established. However, patients with less chronic and less severe heroin dependence benefit more fully from buprenorphine than from a pure opioid agonist like methadone [56].

Studies support buprenorphine as a viable alternative for opioid maintenance therapy. However, its mixed agonist/antagonist action entails special considerations. Buprenorphine may precipitate opioid withdrawal, and patients being switched from short-acting opioids must abstain from illicit opioid use for at least 24 hours before initiating buprenorphine therapy [56,107]. Another drawback is associated with the sublingual route of administration. This administration presents some difficulties because the tablet is relatively large and slow to dissolve under the tongue and swallowing diminishes its effectiveness. Also, the transition to buprenorphine from long-acting opioids is difficult [30]. The ASAM warns that diversion and misuse are possible with buprenorphine, as is physical dependence. Respiratory depression may occur if buprenorphine is used with CNS depressants including alcohol, other opioids, and illicit drugs. Neonatal withdrawal has also been reported after use of buprenorphine during pregnancy. Buprenorphine is not recommended for patients with severe hepatic impairment [55,107].

Higher doses of buprenorphine (12 mg or greater) are more effective than lower doses in reducing illicit opioid use, with some studies reporting similar efficacy to methadone on major treatment-outcome measures. One systematic review was conducted to evaluate buprenorphine maintenance compared to placebo and methadone maintenance in the management of opioid dependence [157]. Outcomes considered were treatment retention, suppression of illicit drug use, and reduction in criminal activity and mortality. A total of 31 trials involving 5,430 participants with moderate- to high-quality evidence were included in the review. According to the data reviewed, buprenorphine retained participants better than placebo at low doses (2–6 mg), at medium doses (7–15 mg), and at high doses (≥16 mg). Only high-dose (≥16 mg) buprenorphine was more effective than placebo at suppressing illicit opioid use (as measured by urinanalysis). Buprenorphine in flexible doses (i.e., adjusted to participant need) was less effective than methadone in retaining participants, and for those retained in treatment, no difference was observed in suppression of illicit opioid use. In low fixed-dose studies, methadone (≤40 mg) was more likely to retain participants than low-dose (2–6 mg) buprenorphine. However, there was no difference between medium-dose (7–15 mg) buprenorphine and medium-dose (40–85 mg) methadone in retention or in suppression of illicit opioid use. Similarly, there was no difference between high-dose (≥16 mg) buprenorphine and high-dose (≥85 mg) methadone in retention or suppression of self-reported heroin use [157]. In a study of 34,000 Massachusetts Medicaid beneficiaries, the incidence of relapse was greater with buprenorphine than with methadone [156]. The primary advantage of buprenorphine over methadone is its superior safety profile [30].

Slow-Release Oral Morphine

Slow-release formulations of morphine that are effective with once-daily dosing are a viable alternative in the treatment of opioid dependence. These formulations considerably delay time to peak concentration after oral administration, resulting in delayed onset of action and making the reinforcing effects very weak when it is administered orally. Several trials have suggested that slow-release morphine has approximately equal efficacy with methadone; however, there is no definitive evidence of this effect [30,158,159]. Slow-release oral morphine may be a viable alternative for patients who are intolerant to methadone [160].

Diacetylmorphine (Heroin)

The pharmacokinetic properties of heroin make it less than ideal for use as a maintenance drug, and the main rationale for heroin maintenance has been the treatment of patients who simply do not respond to any other treatment modality. Although preliminary results seem to be positive, before suggesting that heroin treatment may have a place with a subpopulation of patients, further studies using standardized protocols are needed. Significantly, studies so far clearly indicate that heroin maintenance, with or without methadone, can be implemented safely. The relatively high cost of heroin maintenance compared with standard methadone or buprenorphine treatment is a drawback of this approach. However, at least one study suggests that heroin combined with methadone may be more cost-effective than methadone alone [30].

The results of medically prescribed heroin administration to chronic, treatment-refractory, heroin-dependent patients have been detailed in two reports. One report from Switzerland concluded that supervised medical prescription of heroin was associated with favorable treatment retention, reduced illicit drug use, reduced criminality, and improved health outcomes and social functioning. These findings were also reported in a controlled trial from Spain and Germany [77]. Research projects were also performed in the Netherlands, Canada, and England, and others are planned in Belgium and Denmark. Based on the positive outcomes thus far, heroin maintenance has become routine treatment for otherwise untreatable heroin addicts in Switzerland, the Netherlands, Germany, and England and is being recommended in Canada [161,162].

The addition of any psychosocial support modality to agonist replacement therapy significantly reduces illicit use during treatment, and treatment retention and results at follow-up are also improved [140,141]. There are two general types of psychosocial therapy used for treating addictive disorders. The first includes therapies developed for treating depression and anxiety that were later adapted for treating persons with addictive disorders, examples of which include cognitive behavioral therapy, supportive expressive therapy, and interpersonal therapy. The second type includes therapies developed specifically for persons with addictive disorders, such as the closely-related motivational interviewing and motivational enhancement therapy [163].

Drug counseling, another approach specific to addictive disorders, emphasizes abstinence, involvement in 12-step programs, and assistance with social, family, and legal problems. Drug counseling is not considered psychotherapy because it focuses on behaviors and external events rather than the intrapsychic processes [163].

Most studies of psychotherapy with opioid-dependent patients have been conducted in methadone programs and are actually pharmacotherapy/psychotherapy studies. In addition to pharmacologic intervention, methadone programs typically use behavioral contingencies that are based on cessation of illicit drug use and other improvements [163].

A review of the literature on psychosocial therapy outcomes with opioid-dependent patients receiving methadone has found evidence of an interaction between measures of psychiatric symptoms, therapy assignment, and outcomes [163]. Patients with minimal psychiatric symptoms did equally well with drug counseling alone or with drug counseling plus supportive expressive therapy or cognitive-behavioral therapy. Patients with moderate-level symptoms did somewhat better if they received additional psychotherapy, and patients with more severe psychiatric symptoms had substantially better outcomes with additional psychotherapy than with drug counseling alone. Improvements were observed in employment, legal, psychiatric, and drug use indices. Patients with opioid dependence and antisocial personality disorder did not benefit from additional psychosocial therapy beyond drug use reduction, but patients with opioid dependence, antisocial personality, and depression exhibited improvement in multiple areas [163].

Therapist variables played an important role in outcome, with better results associated with therapists who formed a positive, helping relationship with the patient. There is also some evidence that the best patient outcomes come from methadone programs with a higher level of services that include counseling, medical, and psychiatric services [163].

The primary goal of abstinence-oriented interventions is cure, which is defined as long-term, stable abstinence from all opioids. Abstinence is achieved in two phases: detoxification and relapse prevention. Outcomes in abstinence-oriented programs are generally poor [77].

The primary goal of pharmacotherapy during detoxification is to alleviate opioid withdrawal severity and associated distress/medical complications and to enhance patient motivation to continue treatment. Withdrawal can also be reduced by psychosocial measures, such as contingency management or counseling, and as discussed, the addition of psychosocial therapy to pharmacologic treatment increases efficacy. Buprenorphine and clonidine are both used to manage withdrawal symptoms, but buprenorphine's advantages, compared with clonidine, are related to its favorable side effect profile and positive effects on well-being and psychosocial variables [77].

Opioid Antagonist Therapy

Relapse-prevention programs have traditionally involved long-term residential placement of nine months or more, often using the therapeutic community format. More recently, pharmacotherapeutic agents, such as naltrexone, have been added to reduce relapse risk. A drawback with opioid antagonist therapy is the high dropout rate during detoxification, which results in highly selective patient samples in most of the naltrexone maintenance studies. Naltrexone maintenance or relapse-prevention treatment should be reserved only for those patients who are able to give informed consent, are fully withdrawn from opioids, and have no specific contraindications for this treatment [107]. Relapse prevention with naltrexone may also be suitable for pregnant women who are unable to stabilize on methadone or buprenorphine. Patients should be warned that reduced tolerance following naltrexone treatment may increase the risk of overdose [77].

The primary problem with naltrexone treatment is low compliance, with retention in treatment ranging from 6% to 45% [30,107]. Strategies to improve treatment compliance include combining naltrexone maintenance with contingency management, involving the provision of vouchers redeemable for goods and services contingent on naltrexone intake and drug-free urines [86]. The authors of one investigation evaluated prescribing patterns for opioid use disorder medications among a commercially insured population in the United States from 2010 to 2014. The evaluation revealed consistently low treatment completion rates for two forms (e.g., injectable, oral) of naltrexone. At 30 days post-initiation, 52% of individuals treated with injectable naltrexone had discontinued treatment, and 70% of individuals treated with oral naltrexone had discontinued treatment. The proportion of patients treated with either form of naltrexone grew over time, but the discontinuation rates were significantly higher compared with individuals treated with sublingual or oral-mucosal buprenorphine/naloxone [164]. Although the focus of this investigation was not on the reasons for treatment discontinuation, it did highlight the poor treatment compliance with naltrexone. The extended-release injectable naltrexone formulation may help overcome the compliance issues associated with the oral formulation [107].

Naltrexone is contraindicated in patients with hypersensitivity reactions to the agent, in patients with current physical and physiologic dependence on opioids, and in patients in acute opioid withdrawal [107]. At present, reviewers conclude "there is no sufficient evidence of efficacy of naltrexone to justify its use in the maintenance treatment of opioid dependence" [165].

Psychosocial Monotherapy

For patients with opioid use disorder for whom opioid use disorder pharmacotherapy is contraindicated, unacceptable, or unavailable, the Department of Veterans Affairs Work Group has found there is insufficient evidence to recommend for or against any specific psychosocial interventions.

(https://www.healthquality.va.gov/guidelines/MH/sud/VADoDSUDCPG.pdf Last Accessed: March 21, 2024)

Strength of Recommendation: Neither for not against

There is no data to support psychosocial interventions as a sole intervention for opioid dependence [140,141]. Psychosocial treatments alone are not adequately proven treatment modalities, nor are they superior to any other type of treatment for opioid dependence [166]. However, psychosocial treatments offered in addition to pharmacologic detoxification treatments are effective in terms of treatment completion, opioid use, and participant abstinence at follow-up [141].

Twelve-step programs for opioid use disorder include Narcotics Anonymous (NA) and Methadone Anonymous (MA) and are modeled after Alcoholics Anonymous (AA), an abstinence-based support and self-improvement program that is based on the 12-step model of recovery. AA is widely considered the most successful treatment for alcoholism and has helped hundreds of thousands of alcoholics achieve sobriety [167]. The 12-step model emphasizes acceptance of dependence as a chronic, progressive disease that can be arrested through abstinence but not cured. Additional elements include spiritual growth, personal responsibility, and helping other addicted persons. By inducing a shift in the consciousness of the addict, 12-step programs offer a holistic solution and are a resource for emotional support [167]. Although research on efficacy and patient outcomes in NA and MA is very limited, many prominent researchers emphasize the important role ongoing involvement in 12-step programs plays in recovery from substance abuse [168].

The understanding of drug dependence as a chronic and relapsing disorder has helped professionals gain a better comprehension of the vital role played by 12-step programs. Every patient attempting to recover from a substance use disorder will encounter a time when he or she faces urges to use without the resources or assistance of healthcare professionals. Twelve-step programs are not considered treatment, nor are they intended as substitutes for treatment. Instead, they are organizations that provide ongoing and indefinite support in the achievement and maintenance of abstinence and in personal growth and character development [168].

Part of the effectiveness of NA and MA is related to their ability to provide a competing and alternative reinforcer to drug use. Involvement in 12-step programs can enhance the quality of social support and the social network of the member, a potentially highly reinforcing aspect the person stands to forfeit if they resume drug using. Other reinforcing elements of 12-step involvement include recognition for increasingly durable periods of abstinence and frequent awareness of the consequences of drug and alcohol use through attendance of meetings [169]. Research shows that establishing a pattern of 12-step program attendance early in treatment predicts the level of ongoing involvement. Emphasis and facilitation of early engagement in a 12-step program involvement are key [170].

Narcotics Anonymous

Relative to the more established AA, there are few studies published on NA. However, some research has revealed important information about how NA functions to help both new and long-term members abstain from opioids and other drugs. Being active as an NA sponsor over a one-year period was found to be strongly associated with substantial improvements in sustained abstinence rates for the sponsors. This suggests that providing direction and support to other newer addicts is a way to enhance the likelihood of one's own abstinence [171]. In addition to being a sponsor, having a sponsor also is associated with positive outcomes. One analysis explored the predictors and outcomes of having a 12-step sponsor among individuals receiving treatment for stimulant use disorders [172]. Four types of 12-step groups were evaluated: NA, AA, Cocaine Anonymous, and Crystal Meth Anonymous. Factors evaluated were the extent to which participants obtained sponsors, the extent to which other predictors (e.g., beliefs, expectations) were associated with having a sponsor, and the effect of sponsorship at the end of treatment. Participants in the 12-step facilitation intervention had higher sponsorship rates at the end of treatment and at three-month follow-up, and end-of-treatment sponsorship predicted a higher likelihood of abstinence and no drug-related problems at follow-up [172].

Improvement in psychologic functioning as a result of NA involvement has been observed by Christo and Sutton [173]. Among the 200 NA members in their study, those who had been off drugs and involved with NA for longer periods tended to have lower trait anxiety and higher self-esteem scores, with those abstinent for more than three years exhibiting levels of anxiety and self-esteem similar to those of a comparison group of 60 students from a vocational training college [173].

Methadone Anonymous

MA was begun in 1991 when a staff member of a methadone maintenance treatment clinic in Baltimore attended an NA meeting and observed a woman receiving an "Anniversary Chip" in recognition of abstinence from heroin, only to be told to return the chip when she shared that methadone maintenance helped make it possible. This staff person went on to develop a 12-step program for methadone patients [174].

MA is based on the belief that "methadone is a therapeutic tool of recovery that may or may not be discontinued in time, dependent upon the needs of the individual," and that continued abstinence from drugs of abuse, including alcohol, is the foremost goal of recovery [175]. Most MA meetings are hosted by methadone clinics, and there are more than 1,000 MA clinics worldwide [176].

There are very few published studies involving MA. One study found that, similar to other 12-step programs, MA members undergo a spiritually-mediated transformation in their recovery process, with members describing methadone as the core of the group experience and an aid to spiritual transformation [177]. Length of time in MA has been found to be associated with reductions in the use of other substances as well, including alcohol, cocaine, and marijuana. Clients in methadone maintenance programs have rated components of MA to be significantly more helpful to recovery than methadone treatment components, suggesting that MA participation has benefits not available in professionally-driven methadone therapy programs [174].