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Methadone

Opioidprescriptionoral · inferred

Long-acting mu-opioid agonist and NMDA antagonist used for opioid use disorder maintenance and chronic pain. Extreme interindividual PK variability (half-life 8-59 h) and dose-dependent QTc prolongation necessitate slow titration and ECG monitoring at higher doses. Typical MMT doses 60-120 mg/day; pain dosing often lower and divided. Narrow therapeutic window.

Projected serum levels — 40 mg, once daily

Methadone
Methadone modeled serum levels, 40 mg once daily over 15 days Population-based pharmacokinetic estimate. Steady state reached after approximately 3 days. 0 25 50 75 100 Day 0 Day 4 Day 8 Day 11 Day 15 Time on a regular schedule ≈ steady state · day 3
Methadone modeled serum levels with a loading dose of 86.1 mg, then 40 mg once daily The first dose is larger so levels approach steady state faster. 0 25 50 75 100 Day 0 Day 4 Day 8 Day 11 Day 15 Time on a regular schedule

Maintenance schedule: 40 mg once daily (oral).

Loading schedule: 86.1 mg on day 1, then 40 mg once daily — reaching therapeutic levels sooner.

Modeled steady state after ~3 days: peak ≈ 63.9 mg, trough ≈ 36.6 mg body load. Population-based estimate over 15 days for a 40 mg dose at a 70 kg reference body mass — the interactive app scales curves to your doses, timing, and body mass.

Key facts

Category
Opioid
Route modeled
Oral
Model confidence
inferred
Half-life
27 h
Common dose
40 mg
Suggested maximum
120 mg/day
Reference dose range
2.5–120 mg (single dose)
Suggested cadence
once daily
Validated against
10 mg oral — Cmax 0.075 mg/L at 3 h

Documented interactions

  • danger
    1,4-BDO (1,4-Butanediol) + Methadone Contraindicated

    1,4-BDO converts to GHB. Methadone has long-half-life respiratory depression. Combination stacks unpredictably and is frequently fatal.

  • danger
    1P-LSD (1-Propionyl-LSD) + Methadone Serotonin risk

    1P-LSD (1-Propionyl-LSD) and Methadone both have serotonergic activity. Risk of serotonin syndrome (hyperthermia, rigidity, autonomic instability, altered mental status).

  • danger
    25I-NBOMe + Methadone Serotonin risk

    25I-NBOMe and Methadone both have serotonergic activity. Risk of serotonin syndrome (hyperthermia, rigidity, autonomic instability, altered mental status).

  • danger
    2C-I (2,5-Dimethoxy-4-iodophenethylamine) + Methadone Serotonin risk

    2C-I (2,5-Dimethoxy-4-iodophenethylamine) and Methadone both have serotonergic activity. Risk of serotonin syndrome (hyperthermia, rigidity, autonomic instability, altered mental status).

  • danger
    2C-B (4-Bromo-2,5-dimethoxyphenethylamine) + Methadone Serotonin risk

    2C-B (4-Bromo-2,5-dimethoxyphenethylamine) and Methadone both have serotonergic activity. Risk of serotonin syndrome (hyperthermia, rigidity, autonomic instability, altered mental status).

  • danger
    4-AcO-DMT (Psilacetin) + Methadone Serotonin risk

    4-AcO-DMT (Psilacetin) and Methadone both have serotonergic activity. Risk of serotonin syndrome (hyperthermia, rigidity, autonomic instability, altered mental status).

Serum checks 231 modeled interaction pairings for methadone across your whole stack — absorption conflicts, enzyme inhibition, and nutrient depletion included.

Research behind this entry

  1. Interindividual variability of the clinical pharmacokinetics of methadone: implications for the treatment of opioid dependence Eap CB, Buclin T, Baumann P · Clinical Pharmacokinetics, 2002 DOI

    Definitive PK review documenting methadone's extreme variability (half-life 8-59 h, bioavailability 41-99%), CYP3A4/CYP2B6 metabolism, stereoselective PK, and implications for dose individualization in OUD.

  2. QTc interval screening in methadone treatment Krantz MJ et al. · Annals of Internal Medicine, 2009 DOI

    Consensus recommendations on ECG screening before and during methadone therapy, driven by evidence of dose-dependent QT prolongation and torsades de pointes case reports.

  3. Methadone maintenance therapy versus no opioid replacement therapy for opioid dependence Mattick RP et al. · Cochrane Database of Systematic Reviews, 2009 DOI

    Cochrane review confirming methadone maintenance is significantly more effective than non-pharmacological approaches for treatment retention and heroin use reduction in OUD.

3 published studies referenced in the app, each with a plain-language summary.