Isomethadone
Encyclopedic
Encyclopedic
Typical encyclopedia coverage. Cross-reference for important decisions.
- 2 corroborating sources
- 1 ROA with full dose ladder
- duration data present
- 29 combo interactions documented
- classified Tentative
- 2 corroborating sources
- 1 ROA with full dose ladder
- duration data present
- 29 combo interactions documented
- classified Tentative
Summary
Once a pharmaceutical drug also known as isoamidone, this opioid analgesic and methadone analogue was withdrawn from the market and is seldom seen today. Rarely abused, though reports state it is around twice as potent as methadone, and more euphoric.
Dose Information
| ROA | Light | Common | Strong | Heavy |
|---|---|---|---|---|
| Oral | 1.5-2.5mg | 2.5-7.5mg | 7.5-15mg | 15mg+ |
Onset, Duration & After-effects
| ROA | Onset | Peak | Total |
|---|---|---|---|
| Oral | 30-90 min | 30-40 hrs | 30-40 hrs |
Effect Profile
Scores (0–10) curated from multiple sources:
- Effect keyword matching from PsychonautWiki catalog
- Weighted by importance: core (×3), major (×2), minor (×1)
Moderate euphoria with mild pain relief and itching/nausea, low sedation
Tolerance
No tolerance chart. Our decay curves for opioids were estimates, and a curve can make tolerance look longer-lasting than it is, which is the dangerous direction.
Opioid tolerance drops fast when you stop, and even a few days off can be enough, so a dose that used to be normal can now stop your breathing. Overdose deaths rise sharply after prison, detox or leaving treatment, and tolerance also falls during a hospital stay. After any break, start with a much smaller amount, try a test dose first, don't use alone, and keep naloxone within reach. Alcohol, benzodiazepines, gabapentinoids and other sedatives make an opioid overdose much more likely.
Sources: FRANK: heroin · National Harm Reduction Coalition · WHO: opioid overdose · Merrall et al. 2010 · Binswanger et al. 2007 · Strang et al. 2003 · FDA 2019: gabapentinoids and breathing
Effects
Effect glossary — · full glossary
Combinations
Cross-Check Isomethadone with another substanceHelpful Links
Add to PsychonautWiki Journal
The PsychonautWiki Journal logging app doesn't include every substance. To track Isomethadone there, start adding an ingestion, search for the name, and choose to add it as a custom substance. Paste these values:
Isomethadone Source: SubstanceSearch (substancesearch.com) Oral dose (mg): light 1.5-2.5 · common 2.5-7.5 · strong 7.5-15 · heavy 15+ Oral duration: onset 0.5-1.5h · peak 30-40h · total 30-40h · after-effects 1-24h Note: ranges are harm-reduction guidance, not a prescription. Start low, go slow, and test your substances.
Tip: for quicker logging you can also add a Custom Unit in the app, e.g. common dose ~ 5 mg (Oral).
The app keeps custom substances simple, so the full dose ranges live in the description text above. Ranges are harm-reduction guidance, not a prescription.
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