Opioid use disorder

What research says

Prevalence. US: an estimated 6-9 million people meet OUD criteria annually, with somewhat higher lifetime prevalence. Globally, estimates vary. Rates vary substantially by region, community, and historical period.

Mortality. OUD is associated with substantially elevated mortality. Overdose is the leading cause of death in adults under 50 in the US in recent years. MOUD reduces all-cause mortality by roughly half in most studies. High-risk periods for overdose include: after release from incarceration, after inpatient detoxification without ongoing treatment, after any period of reduced tolerance, and any use of the illicit supply given fentanyl contamination.

Treatment evidence. The evidence for MOUD is among the strongest in psychiatry.

• Methadone: Cochrane reviews and multiple RCTs demonstrate substantial reductions in illicit opioid use, mortality, criminal activity, and HIV transmission. In use since the 1960s. Delivered in the US through federally regulated opioid treatment programs (OTPs).
• Buprenorphine: multiple RCTs demonstrate similar efficacy for maintenance treatment. Available through office-based prescribing since 2000 (Drug Addiction Treatment Act). Removal of the X-waiver requirement in 2023 expanded access. Partial agonist properties reduce overdose risk. Combined with naloxone in most formulations to reduce diversion.
• Naltrexone (extended-release injectable): opioid antagonist, blocks opioid effects. Requires opioid-free interval before starting. Trials (particularly Lee 2018 comparison to buprenorphine) show comparable effectiveness once initiated, but induction difficulty limits population impact.

Comorbidity. Very high. Common: - Alcohol use disorder - Other substance use disorders (particularly cocaine, methamphetamine, benzodiazepines, cannabis) - Depression - Anxiety disorders - PTSD - Chronic pain - Hepatitis C (very high rates in injection populations) - HIV in some populations - Various infections related to injection use

What OUD is

Under DSM-5-TR, OUD is diagnosed when a person shows a problematic pattern of opioid use leading to clinically significant impairment or distress, as manifested by at least two of eleven criteria within a 12-month period:

1. Opioids taken in larger amounts or over a longer period than intended 2. Persistent desire or unsuccessful efforts to cut down or control use 3. Great deal of time spent obtaining, using, or recovering from opioid effects 4. Craving or a strong desire to use opioids 5. Recurrent use resulting in failure to fulfill major role obligations 6. Continued use despite persistent or recurrent social or interpersonal problems caused or exacerbated by opioid effects 7. Important social, occupational, or recreational activities given up or reduced 8. Recurrent use in situations that are physically hazardous 9. Continued use despite knowledge of persistent or recurrent physical or psychological problem caused or exacerbated by opioids 10. Tolerance (needing more for the same effect, or reduced effect with the same amount) 11. Withdrawal (either the characteristic withdrawal syndrome or opioid use to relieve or avoid withdrawal)

Note: tolerance and withdrawal do not count when opioids are prescribed and taken as directed under medical supervision.

Severity is specified as mild (2-3 criteria), moderate (4-5), or severe (6 or more).

ICD-11 uses the term "opioid dependence" with similar clinical concepts.

Opioids include prescription analgesics (oxycodone, hydrocodone, morphine, codeine, hydromorphone, oxymorphone), heroin, fentanyl and fentanyl analogs (a very potent synthetic opioid class), methadone (used both for OUD treatment and for pain), buprenorphine (partial agonist used for OUD and pain), and tramadol.

The fentanyl era

Understanding OUD in current context requires understanding fentanyl.

Fentanyl is a synthetic opioid roughly 50 to 100 times more potent than morphine. It has legitimate medical uses in anesthesia and cancer pain. Since around 2013, illicitly-manufactured fentanyl (IMF) has increasingly contaminated the illicit drug supply in North America. Fentanyl is often mixed into or sold as heroin, counterfeit prescription pills, and increasingly non-opioid drugs (cocaine, methamphetamine, benzodiazepines).

Overdose consequences. Fentanyl's potency and the inconsistency of illicit dosing produce dramatically elevated overdose risk. CDC data shows overdose deaths rising sharply since 2013, with synthetic opioids (predominantly fentanyl) driving the increase. Peak US overdose deaths passed 100,000 annually for the first time in 2021, with the large majority involving synthetic opioids.

Implications for care. In current US context: - Any illicit opioid should be presumed to potentially contain fentanyl - Naloxone should be widely available and accessible without judgment - Fentanyl test strips and other harm reduction tools have public-health value - Treatment access must be lower-threshold given the escalating mortality risk - Prescription-only OUD is now unusual in patients who use illicit drugs

Xylazine ("tranq") has increasingly appeared in the illicit opioid supply since around 2020. Xylazine is a veterinary sedative that does not respond to naloxone, complicates overdose response, and produces severe wound complications with repeated use.

What it feels like

The internal experience of OUD varies substantially depending on the phase and the person's history.

Early use. Opioids produce a distinctive combination of pain relief, sedation, and a specific kind of felt calm or well-being. For patients using prescribed opioids, the experience may be primarily pain relief with modest additional effects. For patients using recreationally, the "high" varies with dose, drug, and route.

Development of tolerance. With regular use, the person needs more opioid to achieve the same effect. Tolerance develops over days to weeks depending on use pattern. Once tolerance is present, using pre-tolerance doses in someone with reduced tolerance (after a break, after incarceration, after treatment) produces high overdose risk.

Physical dependence and withdrawal. With regular use, the body adapts to the presence of opioids and produces withdrawal symptoms when opioids are stopped or reduced. Withdrawal typically includes muscle aches, restlessness, sweating, gooseflesh, dilated pupils, runny nose and tearing, yawning, insomnia, nausea, vomiting, diarrhea, abdominal cramping, and intense craving. Symptoms peak at 24-72 hours after last use for short-acting opioids, longer for methadone. Not typically life-threatening in isolation but often described as one of the most unpleasant experiences the person has had.

Cravings. Persistent, often intense drive to use opioids, triggered by environmental cues (places, people, times of day), emotional states (stress, depression, anxiety, boredom), physical states (pain, insomnia), and internal cues.

Loss of control. Using more than intended, being unable to stop despite intention, and continuing to use despite adverse consequences are core features.

Chronic use. Life often organizes around the substance: obtaining it, using it, recovering, and managing withdrawal. Other activities and relationships often narrow. The person may recognize the pattern and want to change but find it very difficult.

Concurrent physical illness is common: injection-site infections, cellulitis, endocarditis, hepatitis C, HIV, opportunistic infections, and various trauma-related consequences.

Emotional experience. Depression, anxiety, and grief (over losses accumulated during use) are common. Many patients report using in part to manage psychological distress that predates or was exacerbated by the OUD.

Differential diagnosis and diagnostic considerations

Prescribed opioid use for pain. Patients on prescribed opioids may develop physical dependence without OUD. Physical dependence alone is not OUD. Assessment considers whether behavioral criteria are met.

Other substance use disorders. Polysubstance use is common. Assessment considers each substance separately.

Chronic pain conditions. Pain that drives opioid use complicates the treatment picture. Adequate pain management alongside OUD treatment is important.

Depression and anxiety. Very commonly co-occur. Sometimes precede OUD; sometimes result from it. Treatment addresses both.

PTSD. Common co-occurrence, particularly in populations exposed to trauma (veterans, survivors of interpersonal violence). Substance use often serves as symptom management.

Bipolar disorder and other primary psychiatric conditions. Present in a subset. Treatment addresses both.

Why it happens

Neurobiology. Opioids act on mu-opioid receptors, producing analgesia, sedation, respiratory depression, and (in the mesolimbic dopamine system) reinforcement. Repeated use produces adaptations that maintain compulsive use even in the face of adverse consequences. Long-term changes in stress response, executive function, and reward processing all contribute.

Genetics. Substance use disorders show substantial heritability, with the OUD estimate around 40-60 percent. Multiple genes contribute; no single gene predicts.

Environmental factors. - Prescription: prescription opioid exposure is a well-established route into OUD, though the majority of prescribed patients do not develop OUD. Higher doses, longer durations, and use in patients with prior substance use disorder increase risk. - Trauma exposure: strongly associated with subsequent substance use disorders, including OUD. - Chronic pain: chronic pain conditions that don't respond well to non-opioid treatment are a common precursor. - Untreated psychiatric conditions: depression, anxiety, PTSD, and other conditions are associated with elevated risk. - Social determinants: poverty, unstable housing, unemployment, and lack of access to care all elevate risk.

The prescription-to-illicit-opioid pathway. Historically, many patients with OUD started with prescribed opioids and later moved to illicit opioids as tolerance grew and prescription access was reduced. The current picture is shifting; direct entry via fentanyl (often unknowingly consumed as counterfeit pills or in contaminated supply) is increasingly common, particularly in younger populations.

Assessment

Clinical interview covering the DSM-5-TR criteria. Assessment of:

• Current use pattern: substance(s), route, dose, frequency, source
• Fentanyl exposure risk (essentially universal for illicit opioid users at present)
• Overdose history
• Injection use and infectious risks
• Prior treatment attempts and outcomes
• Chronic pain
• Psychiatric comorbidities
• Social and occupational function
• Legal considerations

Urine drug screen when appropriate for confirming use and monitoring treatment.

Medical workup: infectious disease screening (hepatitis C, HIV, syphilis, TB in high-risk populations), skin examination for injection sites and infection.

Consideration of treatment options, patient preference, and structural access issues.

Treatment

The three FDA-approved medications for OUD are the core of evidence-based treatment.

Methadone.

• Full opioid agonist
• Once-daily oral dosing
• Delivered through federally regulated opioid treatment programs (OTPs), often called methadone clinics
• Requires daily or near-daily attendance in early treatment, with take-home doses earned over time based on stability
• Suicide, overdose, and all-cause mortality substantially reduced compared to no treatment
• Long acting; withdrawal management with methadone requires slow tapering
• Structural access is a barrier: many rural areas have no OTP within reasonable distance (see mental health shortage areas for how federal shortage designations work)

Buprenorphine (Suboxone, Zubsolv, Sublocade, Brixadi).

• Partial opioid agonist (with a ceiling effect for respiratory depression, reducing overdose risk)
• Sublingual, buccal, or injectable formulations
• Can be prescribed in office-based settings (X-waiver requirement removed in 2023)
• Induction requires the patient to be in mild-to-moderate withdrawal to avoid precipitated withdrawal
• Effective for both maintenance and (less commonly) tapered withdrawal
• Multiple long-acting injectable formulations now available (monthly Sublocade, weekly and monthly Brixadi)
• Frequently combined with naloxone in sublingual formulations to reduce diversion risk

Naltrexone (extended-release injectable, Vivitrol).

• Opioid antagonist
• Monthly intramuscular injection
• Requires 7-14 day opioid-free period before initiation (a major barrier)
• Once initiated, effective at blocking opioid effects
• Does not produce dependence, no withdrawal on discontinuation
• Lee 2018 X:BOT trial found buprenorphine and extended-release naltrexone comparably effective once initiated, but naltrexone had much lower successful initiation rates

Choice of medication depends on patient preference, prior experience, access to specific treatment settings, other medical considerations, and structural factors. Patient preference is important; forced medication choice reduces engagement.

Duration of treatment. OUD is a chronic condition; treatment is typically long-term. No fixed endpoint. Discontinuation of MOUD is associated with elevated mortality. Discussions of medication discontinuation should involve the specific patient, the specific circumstances, and the specific risks.

Psychosocial treatment. Complements but does not replace medication.

• Cognitive-behavioral therapy for substance use disorders
• Contingency management (evidence-based for stimulant use disorders; some evidence for opioid)
• Twelve-step facilitation and mutual-help engagement (though many 12-step groups have historically had bias against MOUD; this is changing)
• Family therapy
• Case management
• Housing support
• Employment support

Overdose prevention.

• Naloxone distribution to patients, family, and community
• Fentanyl test strip access
• Sterile injection equipment through syringe services programs
• Contact with overdose prevention centers where available (recently piloted in NYC and elsewhere)

Treatment of co-occurring conditions.

• Depression, anxiety, PTSD: standard evidence-based treatments
• Chronic pain: multimodal pain management, non-opioid options, adjunctive medications
• Hepatitis C: direct-acting antivirals have very high cure rates and should be offered
• HIV when present: standard antiretroviral therapy

High-risk transitions require enhanced support.

• Post-incarceration: MOUD should be continued or initiated in jail/prison and continuity ensured on release; overdose risk is extremely high in the immediate post-release period
• Post-inpatient detoxification: MOUD should be initiated during the inpatient stay and continued on discharge
• Loss of insurance or clinic access: bridge planning matters
• Pregnancy and postpartum: MOUD continued through pregnancy; buprenorphine and methadone both safe and evidence-based; not switching medications during pregnancy is preferred

Common comorbidities in detail

Chronic pain is very common. Standard pain management with attention to OUD status; multimodal approaches; caution about additional opioid exposure. Buprenorphine and methadone both have analgesic properties.

Alcohol use disorder frequently co-occurs and increases overdose risk. Integrated treatment addressing both.

Stimulant use (cocaine, methamphetamine) is increasingly common in polysubstance patterns. Contingency management has the best evidence for stimulant use disorders.

Benzodiazepine use substantially increases overdose risk when combined with opioids. Careful management of any benzodiazepine prescribing, and treatment of illicit benzodiazepine use, matters.

Depression is very common. Treatment produces meaningful gains. SSRIs are typically first-line; caution about pharmacological interactions and QT effects with methadone.

Anxiety and PTSD are very common. Trauma-focused treatment when appropriate. Non-benzodiazepine treatment preferred given overdose risk.

Hepatitis C should be offered treatment. Direct-acting antivirals produce cure rates over 95 percent.

HIV when present. Standard antiretroviral therapy.

Endocarditis and other injection-related infections are life-threatening and require aggressive treatment.

Cognitive changes with long-term use, particularly with heavy use, are documented but variable.

Cultural and structural considerations

Race and access. Historical and current disparities in access to MOUD are documented. Buprenorphine has been more available to White patients; methadone (with its more restrictive OTP structure) has been more available to Black and Hispanic patients. Punitive rather than treatment responses have been more common for Black and Hispanic patients. Addressing these disparities requires structural change beyond individual clinical practice.

Criminalization. Drug possession remains criminalized in most US jurisdictions. Involvement with the legal system worsens outcomes and creates barriers to treatment. Diversion programs and drug courts have mixed evidence.

Insurance and access. Prior authorization requirements, coverage variability, and clinic access issues remain barriers despite the strong evidence base for MOUD.

Stigma. Against people with OUD and against the medications themselves remains a major barrier to care. Many 12-step groups have historically opposed MOUD; this position is inconsistent with the evidence but persists.

Populations with specific needs. Pregnant women, adolescents, people in the criminal-legal system, people experiencing homelessness, and rural populations all face specific access barriers and often benefit from specific approaches.

Living with OUD

For the person. OUD is a chronic condition that responds to sustained treatment. Being on MOUD long-term is not failure; it's evidence-based care. Building a life that supports recovery includes reliable access to medication, treatment of co-occurring conditions, connection with supportive people, and often changes in social and physical environment. Setbacks (returns to use, missed doses, relapses) are common features of chronic disease treatment and don't indicate treatment failure; they indicate the need for continued or intensified treatment. Naloxone should be accessible.

For family or partners. Understanding that OUD is a chronic medical condition and that MOUD is evidence-based treatment reduces conflict about the person's care. Having naloxone available and knowing how to use it matters. Setting limits based on your own needs is legitimate; treating the person as a moral failure is not helpful. Support groups for family members (Nar-Anon, Al-Anon, SMART Family and Friends) can be useful.