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Heroin

Follow one dose of heroin from the moment it enters the body until the last of it leaves.

Heroinprodrug6-MAMactiveMorphineactiveM3G~60%, no pain reliefM6G6–10%, activeUrine~87% in 72 h

The clock, on a log scale

Each bar runs from the dose to about five half-lives, roughly when 97% of that molecule has been converted or cleared. The scale is logarithmic so minutes and days fit on one line.

  1. 0 mindose

    Dose enters the body

    route decides the first stop

    Injected or smoked: heroin skips the liver's first pass and crosses into the brain very quickly.1 Heroin itself binds the μ-opioid receptor only weakly. Most of the effect comes from what it turns into.1 Swallowed: the liver breaks it down on the first pass, so it acts as a delivery system for morphine.1

  2. 2–3 minheroin half-life

    Heroin → 6-MAM

    hCE-2 (liver)hCE-1pseudocholinesterase (blood)6-MAM is active

    Enzymes called esterases snip off one acetyl group. The liver enzyme hCE-2 is by far the fastest at this step.3 Heroin's half-life is only 2–3 minutes,1 so it is mostly gone within about 15 minutes. A small share becomes inactive 3-MAM instead.1

    Speedballs: cocaine is broken down by the same esterases. In lab tests, cocaine slowed both of heroin's breakdown steps by competing for those enzymes.3 TripSit rates opioids with cocaine as Dangerous.6
  3. ~36 min6-MAM half-life

    6-MAM → morphine

    hCE-2 (liver)morphine is active

    6-MAM is active at the opioid receptor in its own right.1 Its half-life is listed as 0.6 hours.2 hCE-2 removes the second acetyl group to make morphine.3

    Drug tests: 6-MAM only comes from heroin, so finding it in urine confirms heroin rather than codeine or morphine. Trace amounts show up for about 6–8 hours after use.2 Wikipedia marks this "citation needed"
  4. ~2 hmorphine half-life

    Morphine → M3G and M6G

    UGT2B7 (liver)M3G: no pain reliefM6G: active

    The liver enzyme UGT2B7 attaches a sugar group (glucuronidation). About 60% becomes M3G, which doesn't bind opioid receptors. 6–10% becomes M6G, which does, at about half the strength of morphine.4 Morphine's half-life is about 120 minutes.4

    Effects outlast heroin itself: heroin is gone within minutes, but effects last 4–5 hours because its active metabolites keep working.1
  5. up to 72 hexit

    Out through the kidneys

    urine ~90%bile (rest)

    About 90% leaves through the kidneys as glucuronides and the rest through bile.1 About 87% of a morphine dose is in the urine within 72 hours.4 Standard opiate screens cross-react with these metabolites.1

    Kidneys matter: a review of heroin-assisted treatment found modest effects of kidney impairment on heroin's metabolites and recommended monitoring kidney function. Liver impairment showed no clinically relevant effect.5

Sources

  1. Wikipedia, Heroin (pharmacokinetics section and infobox), CC BY-SA
  2. Wikipedia, 6-Monoacetylmorphine, CC BY-SA
  3. Kamendulis LM et al. Metabolism of cocaine and heroin is catalyzed by the same human liver carboxylesterases. J Pharmacol Exp Ther 1996;279(2):713–7. PubMed 8930175
  4. Wikipedia, Morphine (pharmacokinetics), CC BY-SA
  5. Rook EJ et al. Pharmacokinetics and pharmacokinetic variability of heroin and its metabolites: review of the literature. Curr Clin Pharmacol 2006;1(1):109–18
  6. TripSit combination chart (combos.json, read 2026-10-24)

Half-lives vary between people, doses and routes. This page explains what the body does with a drug. It is not dosing advice.