Source-backed half-life profile
Methadone half-life calculator
Methadone is a long-tail curve with unusually high stakes for overinterpretation.
Every curve begins at 100%. No dose or measured body concentration is assumed.
X-axis: elapsed time. Y-axis: modeled percentage of the relative starting point remaining. The shaded band shows the reported half-life range. This is a mathematical visualization, not a personal concentration estimate.
What a careful reader should notice first
A representative value can make accumulation visible, but methadone treatment context, dose history, formulation, and patient-specific clearance are not calculator problems.
Source angle
The important source habit is to notice ranges and population context. A single midpoint is useful for a visual, not for care decisions.
Do not use it for
Do not use this page for induction, tapering, withdrawal timing, pain control, overdose risk, or medication changes.
Best next step
Read steady state and accumulation, then compare with buprenorphine and naloxone.
Methadone: evidence and interpretation notes
Why 24 hours is only a plotting choice
Methadone has a notably broad reported elimination range. This page uses 24 hours because it produces a readable representative curve within the linked labeling range of 8 to 59 hours. The range is more important than the midpoint: individual clearance, dose history, interactions, and the population being studied can all change the observed terminal half-life.
With the 24-hour input, the normalized curve reaches 50% after one day, 25% after two days, and about 3% after five days. That neat progression is the equation working as designed; it is not evidence that a particular person’s methadone concentration follows the same schedule.
Accumulation is the central context
Methadone’s elimination can be slower than the change in its noticeable effects, and repeated administration can create overlap before prior exposure has fully declined. The pharmacokinetics review provides the broad interpretive context, while DailyMed anchors the product-specific range. PubChem is included for identity and terminology, not as the numerical source.
| Evidence source | What it contributes | Important limit |
|---|---|---|
| DailyMed injection labeling | Product-specific range and repeated-administration context | Injection labeling is not interchangeable with every route or treatment setting |
| Methadone pharmacokinetics review | Absorption, distribution, hepatic metabolism, interactions, and special populations | A broad review cannot yield a personalized correction to the 24-hour line |
| PubChem identity record | Compound identity | It does not support the selected value |
The review emphasizes that methadone disposition is unusually variable and affected by multiple patient and interaction factors. That evidence supports showing the full range and resisting a false-precision midpoint rather than adding more inputs to the public calculator.
The curve’s value is showing overlap
Use the graph to understand why a wide, long-tailed half-life resists simple timing rules. It is not appropriate for induction, dosing, tapering, pain treatment, withdrawal, or overdose decisions; those questions require direct clinical supervision and the labeling for the relevant formulation.
Reading this curve
HalfLifeDB uses 24 h as a representative input for Methadone after multiple dosing. In the simplified model, about 50.0% remains after 24 hours and about 3% remains after five half-lives, or roughly 5.0 days.
This is a day-scale half-life. Repeated exposure, timing, and source context start to matter more than a single snapshot of the curve. The curve is relative: it does not estimate a person's measured concentration, effects, impairment, or time to clearance.
opioid treatment medication context
Opioid treatment medication pages need careful distinction between pharmacokinetic persistence, clinical treatment context, accumulation, and supervised dosing decisions.
- The curve is not a treatment, induction, tapering, or withdrawal guide.
- Long half-lives can make accumulation context especially important.
- Clinical decisions require supervised care, not a public calculator.
Methadone timeline checkpoints
| Elapsed time | Modeled remaining | Reading note |
|---|---|---|
| 24 h | 50.0% | Meaningful modeled decline, not near-zero |
| 3.0 days | 12.5% | Long-tail portion of the model |
| 5.0 days | 3.13% | Low modeled remainder, not a clearance guarantee |
| 7.0 days | 0.78% | Low modeled remainder, not a clearance guarantee |
| 14 days | 0.01% | Low modeled remainder, not a clearance guarantee |
Nearby profiles by half-life
These entries sit near Methadone within the opioid treatment medication group when sorted by representative half-life. That makes them curve comparisons, not statements about equal potency, effects, or risk.
- Buprenorphine (37 h)
Pharmacokinetics at a glance
| Representative half-life | 24 h |
|---|---|
| Modeled analyte or phase | Methadone after multiple dosing |
| Reported range | 8 h to 2.5 days |
| Curve type | Normalized, first-order decline |
Selection note: Methadone half-life is highly variable; 24 hours is a readable representative value for the educational curve.
Sources and evidence context
A linked record is not automatically proof of the displayed value. Study, labeling, review, and compound identity sources serve different purposes; notes below identify limitations when they are known.
- Official labeling DailyMed label: METHADONE HYDROCHLORIDE INJECTION, SOLUTION [BRECKENRIDGE PHARMACEUTICAL INC].Official labeling used for the broad 8-to-59-hour range and multiple-administration context.
- Identity record PubChem Compound Summary: Methadone.Compound identity record; background only.
- Research abstract PubMed: Pharmacokinetics of methadone.Clinical review emphasizing variable hepatic metabolism, interactions, and special-population differences.
What this page does not answer
- It does not estimate impairment, intoxication, or fitness to drive.
- It does not predict urine, blood, saliva, or hair test results.
- It does not model repeated exposure, tolerance, withdrawal, or interactions.
- It does not replace clinician, pharmacist, toxicologist, or emergency guidance.
Continue with context
- All substance profiles
- Browse the opioid-treatment group
- Compare this curve
- Clearance and volume of distribution
- Bioavailability, route, and formulation
- Active metabolites and parent compounds
- First-order vs nonlinear kinetics
- Detection windows vs half-life
- Reading labels and source quality
Read the medical disclaimer, methodology, and profile review log before using the model for comparison.