MAT for Substance Use Disorder: Buprenorphine, Naltrexone & Methadone

Medication-assisted treatment (MAT) for substance use disorder is built on three opioid-use-disorder medications — buprenorphine (partial mu agonist), naltrexone (mu antagonist), and methadone (full mu agonist) — plus three alcohol-use-disorder agents: naltrexone, acamprosate, and disulfiram. For the PMHNP exam, know each drug's mechanism, the induction cautions (especially precipitated withdrawal with buprenorphine and naltrexone), the monitoring requirements, and the post-X-waiver prescribing landscape.

MAT combines medication with counseling and behavioral therapy; it is the standard of care, not a last resort.

Opioid Use Disorder Medications

Buprenorphine

Buprenorphine is a partial agonist at the mu-opioid receptor (and a kappa antagonist). Because it is a partial agonist, it has a ceiling effect on respiratory depression, making it safer in overdose than full agonists. It binds tightly with high affinity, so it can displace other opioids from the receptor.

• It is often combined with naloxone (an abuse-deterrent formulation); naloxone is poorly absorbed sublingually but precipitates withdrawal if the product is injected.
• Precipitated withdrawal is the key induction hazard: because buprenorphine displaces full agonists but provides less activation, starting it too soon — while full agonists still occupy receptors — can abruptly worsen withdrawal. The patient must be in mild-to-moderate withdrawal (often guided by an objective withdrawal scale) before the first dose.
• Monitor for sedation, constipation, and QT considerations with some formulations; assess liver function periodically.

Methadone

Methadone is a full mu-opioid agonist with a long half-life. It prevents withdrawal and cravings and blunts the euphoria of other opioids.

• In the United States, methadone for opioid use disorder is dispensed only through federally certified opioid treatment programs (OTPs) — it cannot be prescribed for OUD from a general office setting.
• Key risks: QT prolongation (monitor ECG) and respiratory depression, especially during induction and with drug interactions. Its long, variable half-life makes overdose risk highest in the first days of titration.
• No ceiling effect, so overdose risk is higher than with buprenorphine.

Naltrexone

Naltrexone is a competitive mu-opioid antagonist. It blocks the effects of opioids entirely and is available as a long-acting monthly intramuscular injection, which aids adherence.

• Because it is a pure antagonist, the patient must be fully opioid-free — typically 7 to 10 days for short-acting opioids and longer for long-acting — before starting, or it will trigger precipitated withdrawal.
• It has no abuse potential and is not a controlled substance.
• Monitor liver function; counsel that reduced opioid tolerance during treatment raises overdose risk if the patient relapses after stopping.

Exam contrast: buprenorphine = partial agonist (ceiling, safer); methadone = full agonist (no ceiling, OTP-only, QT risk); naltrexone = antagonist (must be opioid-free first).

The Post-X-Waiver Prescribing Landscape

A high-yield update: the DATA 2000 "X-waiver" was eliminated by the Mainstreaming Addiction Treatment (MAT) Act. Practitioners with a standard DEA registration that includes Schedule III authority can now prescribe buprenorphine for opioid use disorder without a separate X-waiver or patient caps.

• A one-time training requirement on treating and managing patients with substance use disorders now applies to DEA registrants more broadly.
• Methadone for OUD still requires dispensing through a certified OTP — that did not change.
• Naltrexone has never required a waiver because it is not a controlled substance.

This change expanded access to office-based buprenorphine and is a frequent exam talking point.

Alcohol Use Disorder Medications

Naltrexone

Naltrexone is first-line for alcohol use disorder. By blocking opioid receptors it reduces the reinforcing, rewarding effects of alcohol, decreasing heavy-drinking days and craving. Available oral and as the monthly injection. Monitor liver function; avoid in patients needing opioid analgesia.

Acamprosate

Acamprosate is thought to modulate glutamate and GABA neurotransmission, restoring balance disrupted by chronic alcohol use. It supports abstinence in patients who have already stopped drinking.

• It is renally excreted, so it is preferred over naltrexone in patients with hepatic impairment, but requires dose adjustment in renal impairment.
• It is dosed three times daily, which can challenge adherence.

Disulfiram

Disulfiram inhibits aldehyde dehydrogenase, causing toxic acetaldehyde accumulation if the patient drinks. The resulting reaction — flushing, nausea, vomiting, tachycardia, and hypotension — is intentionally aversive.

• It requires high motivation and adherence and is best for committed, abstinent patients with supervision.
• Counsel about hidden alcohol sources (mouthwash, certain sauces, some medications).
• Monitor liver function; it is contraindicated in significant cardiac disease and with recent alcohol use.

Monitoring and Safety Across MAT

• Liver function for naltrexone, disulfiram, and buprenorphine.
• ECG for QT with methadone (and consideration with some buprenorphine products).
• Renal function for acamprosate dosing.
• Urine drug screening and PDMP review per program and state requirements.
• Pregnancy: methadone and buprenorphine are the standard of care for opioid use disorder in pregnancy; abrupt withdrawal is discouraged. Naltrexone and the alcohol agents require individualized, current-reference-guided decisions.
• Always pair medication with counseling and recovery support.

Reminder: This article is for board preparation only. Verify induction protocols, contraindications, and monitoring against current FDA prescribing information, SAMHSA guidance, and clinical guidelines before treating a patient.

Bringing It Together for the Exam

When a vignette describes a patient still using opioids who needs office-based treatment, think buprenorphine, and remember they must be in mild-to-moderate withdrawal before induction to avoid precipitated withdrawal. When the stem requires a structured daily program with ECG monitoring, think methadone in an OTP. When the patient is fully detoxed and you want a non-controlled, adherence-friendly option, think long-acting naltrexone — and confirm they are opioid-free. For alcohol use disorder, naltrexone and acamprosate are first-line; disulfiram is for the highly motivated.

These medications intersect with controlled-substance stewardship covered in our ADHD medications review and with the broader black box warnings guide.

Ready to lock in these distinctions? Take a free diagnostic assessment, then practice verified PMHNP questions at PASSNP. Create your free account to start preparing.