Methadone is the original opioid agonist treatment for opioid use disorder — and despite the rise of buprenorphine, it remains uniquely valuable for severe OUD with extensive use history or prior buprenorphine failure. The mechanism is full mu opioid agonism, with the receptor pharmacology of any full agonist: relief of withdrawal and craving, but no ceiling on the dose-effect curve.
- Class
- Full mu opioid agonist
- Mechanism
- Full mu agonist + NMDA antagonist + serotonin/norepinephrine reuptake inhibition (mechanism contributes to pain effects)
- Typical dose
- 60-120 mg/day typical maintenance for OUD; titration over weeks
- Half-life
- Very variable: 8-59 hours (mean ~24 hours), genetic and individual variation
- FDA indications
- Opioid use disorder (dispensed only at federally certified opioid treatment programs in US), chronic pain
- Key adverse effects
- Sedation, constipation, sweating, sexual dysfunction, weight gain, QTc prolongation (dose-dependent — ECG monitoring at higher doses), respiratory depression in overdose
Black box: QTc prolongation and torsades de pointes; respiratory depression; complex pharmacokinetics with risk of accumulation
Dispensed only at federally certified OTPs in the US — daily clinic visits initially, take-home doses earned over time. Effective for severe OUD with extensive use, prior treatment failures. Variable half-life and respiratory depression risk make titration cautious. QTc monitoring at >120 mg/day.
In the United States, methadone for OUD is dispensed only through federally certified opioid treatment programs (OTPs) — the "methadone clinic" infrastructure. Daily clinic visits initially, with take-home doses earned through stability over months or years. The structure provides intensive support and accountability, but is also a substantial barrier — patients must physically come to the clinic, often daily, often early morning, often for years.
- Cost
- Dispensed only at OTPs (federally certified clinics). Daily clinic fees typically $10-20/day; some Medicaid covered fully. Drug itself cheap.
- Generic status
- Generic for decades; OTP-dispensed only for OUD in US.
- Formulary typical
- Different system — OTPs operate under federal SAMHSA certification. Insurance pays OTP fees per session.
- Access friction
- Daily clinic attendance initially. Take-home doses earned through stability over months. The OTP infrastructure is substantial — patient must live within reasonable distance.
Prescriber tip: Refer to certified OTP rather than prescribing yourself (US restriction). For chronic pain methadone (different framework), specialty pain management.
The pharmacokinetics are complex. The half-life ranges from 8 to 59 hours across individuals — a fivefold variation that shapes risk and titration. Steady state takes weeks to achieve. Accumulation continues after acute dosing changes, with risk of overdose emerging days 5-10 as levels build. Early in titration, the patient may feel "just okay" on a dose that will be too high a week later. Cautious slow titration is essential.
QTc prolongation is dose-dependent and particularly prominent above 100-120 milligrams per day. ECG monitoring at higher doses, with screening for risk factors (electrolyte abnormalities, QTc-prolonging combinations, structural cardiac disease). Methadone is one of the most QTc-prolonging psychotropics in routine use.
Drug interactions through CYP3A4 are substantial. Inducers reduce methadone levels (carbamazepine, phenytoin, rifampin) — risk of withdrawal symptoms. Inhibitors raise levels (some antibiotics, antifungals, antivirals) — risk of toxicity. Review the medication list at every visit.
For severe OUD, particularly with extensive use history, prior buprenorphine failure, or patient preference, methadone has unique efficacy. The infrastructure requirement is the practical barrier. Where access exists and the patient can engage with the OTP structure, methadone remains a foundation of OUD treatment.
Methadone treats opioid use disorder through full mu-opioid agonism — highly effective, with the safety constraints that full agonism implies.
Mechanism note: Methadone is the most effective OUD treatment for high-tolerance patients, but full agonism without a ceiling demands structured programs, careful induction, and QTc monitoring.