11.6 Pharmacotherapy for Alcohol & Opioid Use Disorder
Key Takeaways
- Naltrexone is first-line for alcohol use disorder but is avoided in acute hepatitis, hepatic failure and concurrent opioid use.
- Acamprosate is renally cleared and is the preferred agent when significant liver disease precludes naltrexone.
- Buprenorphine must be started only after objective withdrawal has begun, or it will precipitate withdrawal.
- Methadone and buprenorphine both reduce mortality in opioid use disorder, and maintenance is superior to detoxification alone.
- Naloxone should be co-prescribed to patients at risk of overdose and to their household contacts.
Last updated: August 2026
1. Maintenance Pharmacotherapy for Alcohol Use Disorder
Once acute withdrawal is safely managed, pharmacotherapy should be offered to all motivated patients with moderate-to-severe AUD to prevent relapse and sustain abstinence.
Evidence-Based Maintenance Pharmacotherapies
| Pharmacologic Agent | Mechanism of Action & Dosing | Primary Clinical Indication | Organ Clearance & Hepatic / Renal Safety Rules | Key Contraindications & Adverse Effects |
|---|---|---|---|---|
| Naltrexone (First-Line) | Pure Mu-Opioid Receptor Antagonist; blocks endogenous opioid reward pathways and blunts dopamine release in nucleus accumbens.<br/>Dosing: 50 mg PO daily or Vivitrol 380 mg IM monthly | Reduces heavy drinking days, decreases alcohol craving, and prevents binge relapse; highly effective in patients actively trying to reduce consumption | Hepatically metabolized. Safe in mild-to-moderate liver disease, but carries black box warning for dose-dependent hepatotoxicity at high doses | ABSOLUTE CONTRAINDICATIONS:<br/>1. Concurrent opioid use or anticipation of acute opioid analgesia (triggers severe precipitated opioid withdrawal)<br/>2. Acute hepatitis or acute decompensated liver failure (jaundice, encephalopathy)<br/>3. Positive urine opioid screen (requires 7-14 day opioid-free washout) |
| Acamprosate (First-Line) | Modulates NMDA glutamate neurotransmission and enhances GABA; restores neurochemical balance disrupted by chronic alcohol dependence.<br/>Dosing: 666 mg PO TID (two 333 mg tablets TID) | Maintains complete alcohol abstinence in patients who have already achieved detoxification | 100% Renally Excreted Unchanged.<br/>DRUG OF CHOICE IN ADVANCED LIVER DISEASE / CIRRHOSIS (zero hepatic metabolism) | ABSOLUTE CONTRAINDICATION:<br/>Severe Renal Impairment (eGFR < 30 mL/min);<br/>Dose Adjustment: Reduce dose by 50% (333 mg TID) if eGFR is 30-50 mL/min.<br/>Adverse effects: Diarrhea, abdominal cramps |
| Disulfiram (Second-Line) | Irreversible Aldehyde Dehydrogenase (ALDH) Inhibitor; causes immediate toxic accumulation of Acetaldehyde within 10-20 min of ethanol ingestion.<br/>Dosing: 250 to 500 mg PO daily | Maintenance of abstinence in highly motivated, compliant patients with supervised administration (partner/clinic) | Hepatically metabolized | Reaction with Alcohol: Violent flushing, throbbing headache, intractable nausea/vomiting, diaphoresis, chest pain, hypotension, tachycardia, dyspnea, syncope.<br/>Contraindications: Severe coronary artery disease, heart failure, psychosis, pregnancy; severe hepatotoxicity risk |
| Topiramate (Off-Label) | Facilitates GABA-A neurotransmission and antagonizes AMPA/kainate glutamate receptors.<br/>Dosing: Titrated from 25 mg to 150-300 mg/day in divided doses | Reduces craving, heavy drinking days, and promotes abstinence | 70% renally excreted | Sedation, cognitive slowing ("Dopamax"), paresthesias, weight loss, nephrolithiasis, metabolic acidosis, angle-closure glaucoma |
| Gabapentin (Off-Label) | Modulates voltage-gated calcium channels; increases brain GABA levels.<br/>Dosing: 300 to 600 mg PO TID (900-1800 mg/day) | Promotes abstinence, treats comorbid insomnia and mild anxiety during early sobriety | 100% renally excreted; safe in liver disease | Sedation, dizziness, peripheral edema; potential for misuse with opioids; adjust dose for renal impairment |
2. Opioid Use Disorder (OUD): MAT & Acute Overdose Management
Harm Reduction & Public Health Interventions
Comprehensive care for OUD incorporates harm reduction strategies proven to reduce mortality and transmission of bloodborne pathogens:
- Naloxone Co-Prescription & Distribution: Provide take-home intranasal naloxone (4 mg) to all patients with OUD, high-dose prescription opioids (>=50 MME/day), or history of overdose.
- Fentanyl Test Strip Distribution: Enables detection of synthetic fentanyl adulterants in illicit drug supplies.
- Syringe Service Programs (SSPs): Sterile needle access reduces hepatitis C virus (HCV) and HIV transmission by >50%.
- Infectious Screening: Routine screening for HIV, HCV (antibody + RNA reflex), Hepatitis B (HBsAg, anti-HBs, anti-HBc), and surveillance for infective endocarditis (Staphylococcus aureus).
Medication-Assisted Treatment (MAT / MOUD) Modalities
| MAT Modality | Pharmacology & Receptor Profile | Regulatory & Dispensing Rules | Clinical Pearls & Initiation Protocol | Key Safety Warnings & ECG Rules |
|---|---|---|---|---|
| Buprenorphine (+/- Naloxone) | Partial Mu-Opioid Agonist + Kappa-Opioid Antagonist; extremely high receptor binding affinity (displaces full agonists) with a ceiling effect on respiratory depression (safer in overdose) | Can be prescribed in outpatient office-based primary care settings without special SAMHSA waiver (eliminated in 2023) | CRITICAL INITIATION RULE: Patient must be in objective mild-to-moderate opioid withdrawal (COWS score >=8 to 12) prior to initial dose.<br/>Why? Administering buprenorphine while full agonists (fentanyl, heroin, oxycodone) occupy receptors causes sudden displacement, triggering severe precipitated opioid withdrawal | Sublingual formulation combined with Naloxone (Suboxone 4:1 ratio); naloxone has zero sublingual bioavailability but blocks euphoria if tablet is crushed and injected IV.<br/>Long-acting monthly subcutaneous depot (Sublocade) available |
| Methadone | Long-acting synthetic Full Mu-Opioid Agonist; eliminates cravings and withdrawal without inducing euphoria; induces cross-tolerance | Can ONLY be dispensed for OUD through federally certified Opioid Treatment Programs (OTPs) / daily methadone clinics | Excellent retention in treatment; highly effective for heavy fentanyl/heroin dependence.<br/>DRUG OF CHOICE IN RENAL FAILURE / ESRD (eliminated via fecal/hepatic routes, zero renal clearance) | MANDATORY ECG MONITORING: Dose-dependent QTc Prolongation and Torsades de Pointes (especially at doses >100 mg/day or when combined with CYP3A4 inhibitors / other QT-prolonging drugs).<br/>High risk of fatal accumulation in overdose |
| Extended-Release Naltrexone | Full Mu-Opioid Antagonist (Vivitrol 380 mg IM monthly) | Prescribed in standard outpatient medical clinics | MANDATORY 7 TO 14-DAY OPIOID-FREE WASHOUT: Must verify negative urine drug screen and negative naloxone challenge before injection to avoid severe precipitated withdrawal | Decreases opioid tolerance; patients who relapse after stopping naltrexone are at extreme risk of fatal overdose from standard opioid doses due to loss of tolerance |
Acute Opioid Overdose & Naloxone Reversal Protocol
- Clinical Triad of Acute Opioid Overdose:
- Severe Respiratory Depression: Respiratory rate < 8 to 10 breaths/min, shallow chest excursions, or complete apnea with cyanosis.
- Pinpoint Pupils (Miosis): Symmetric pupillary constriction (note: pupils may become dilated late due to severe hypoxic brain injury or co-ingestions like tramadol, meperidine, or sympathomimetics).
- Depressed Mental Status: Stupor, unresponsiveness, or profound coma with hyporeflexia.
- Emergency Resuscitation Protocol:
- Airway & Ventilation First: Immediately establish patent airway, perform bag-valve-mask (BVM) ventilation with 100% Oxygen.
- Naloxone Administration:
- Intravenous / Intramuscular / Subcutaneous: 0.04 mg to 0.4 mg IV initial dose in suspected chronic opioid dependence; titrate incrementally every 2 to 3 minutes.
- Intranasal: 4 mg (single spray in one nostril); repeat in 2-3 minutes in opposite nostril if no response.
- Therapeutic Goal: Restore adequate spontaneous ventilation (RR >10-12 breaths/min) and airway reflexes, NOT complete full arousal. Rapid over-reversal precipitates acute opioid withdrawal storm (severe agitation, vomiting with aspiration risk, severe hypertension) and acute non-cardiogenic pulmonary edema.
- Observation & Continuous Infusion: Naloxone has a short half-life (30 to 90 minutes). Synthetic opioids (fentanyl, methadone, extended-release oxycodone) have prolonged half-lives (hours to days). Patients must be monitored for at least 4 to 6 hours for recurrent respiratory depression. If recurrent toxicity occurs, initiate a continuous IV Naloxone infusion at two-thirds of the effective waking dose per hour.
Test Your Knowledge
A 54-year-old man with a 25-year history of severe alcohol use disorder and biopsy-proven decompensated cirrhosis (Child-Pugh Class C, baseline total bilirubin 4.6 mg/dL, AST 112 U/L, ALT 48 U/L, albumin 2.4 g/dL, INR 1.8, platelet count 62,000/mcL) is admitted to the medical intermediate care unit for management of acute alcohol withdrawal. Twelve hours after his last drink, he is tremulous, diaphoretic, anxious, and tachycardic (heart rate 114 bpm, blood pressure 156/94 mmHg). His CIWA-Ar score is 16. Which of the following represents the most appropriate pharmacotherapy regimen for managing his acute withdrawal, and what is the safest first-line maintenance medication to offer for long-term alcohol relapse prevention following detoxification?
A
B
C
D