Methadone Facts
Opioid;
Description
Methadone is a synthetic opioid of the diphenylheptanone class. Beyond opioid activation, it also blocks glutamate signaling[1] — a combination rare among opioids that shapes both its clinical effectiveness and its risk profile.
Subjective effects include pain suppression, sedation, emotional quieting, and mild euphoria. Effects build over hours rather than arriving as a rush — a sustained warmth and bodily heaviness that feels more like stabilization than intoxication.
Methadone produces rapid physical dependence, and the gap between a therapeutic dose and a fatal one is narrow.[2] Its slow elimination creates an accumulation hazard, and it directly disrupts the heart's electrical rhythm — a toxicity unusual among opioids.[3]
Dose and durationby route · individual sensitivity varies
Starts in 20 – 90 minLasts 10 – 19 hoursAfter-effects 1 – 24 hours
Body and dependence
- Acute toxicity
- Critical
- Chronic toxicity
- High
- Physical dependence
- High
- Psychological dependence
- High
- Withdrawal
- Severe · medical supervision
- Compulsive redosing
- Moderate
Tolerance
- Builds
- Moderate
- Fully resets after
- 10 days
- Carries over to
- morphine;
heroin; oxycodone; hydrocodone; fentanyl; codeine; buprenorphine; tramadol; hydromorphone
Effectslikely at a common dose
- Perception
- none likely · 1 possible
- Body
- Sedation;
Pain suppression; Constipation; Pupil constriction; +20 possible, including Respiratory depression, Nausea, Excessive sweating - Thinking
- none likely · 13 possible, including Compulsive redosing urge, Analysis suppression, Cognitive impairment
- Feeling
- none likely · 6 possible, including Anhedonia, Depression
- Self
- none likely · 6 possible, including Communication suppression, Craving, Social disconnection
- Time
- none likely · 3 possible, including Temporal disorientation
Who shouldn't take it
Combinations62 recorded
Seek help immediately if
- Unresponsive / can't be woken, even to a firm sternal rub
- Slow, shallow, or stopped breathing
- Pinpoint pupils
- Blue/grey lips, fingertips, or skin (cyanosis)
- Limp body; pale, clammy skin
- Choking or gurgling sounds ("death rattle")
- Slow, erratic, or absent pulse
What to do
- Try to wake them — shout their name, firm sternal rub
- Call emergency services immediately
- Administer naloxone if available
- Give rescue breaths (or CPR if there is no pulse)
- Place them in the recovery position
- Stay with them; re-dose naloxone every 2–3 minutes if there is no response
- Reversal agent
- Naloxone (Narcan) — opioid antagonist. May require repeated doses; its effect can wear off before the opioid does.
With prompt naloxone and rescue breathing, reversal is usually rapid. Because naloxone can wear off before the opioid — especially with long-acting opioids (methadone) or high-potency ones (fentanyl) — a period of monitoring is needed even after the person revives.
988 Suicide & Crisis LifelineFireside Project: 62-FIRESIDE
References
- [1]^Ebert B, Andersen S, Krogsgaard-Larsen P (1995) Ketobemidone, methadone and pethidine are non-competitive N-methyl-D-aspartate (NMDA) antagonists in the rat cortex and spinal cord. — Neuroscience Letters PMID:7624018
- [2]^Pelletti G, Giunchi V, Fais P, et al. (2026) Characterizing post-mortem blood concentrations in methadone-related deaths. — International Journal of Legal Medicine doi:10.1007/s00414-025-03620-0
- [3]^Zünkler BJ, Wos-Maganga M (2010) Comparison of the effects of methadone and heroin on human ether-à-go-go-related gene channels. — Cardiovascular Toxicology doi:10.1007/s12012-010-9074-y