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Codeine

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

Codeineweak opioidMorphinevia CYP2D6Norcodeinevia CYP3A4Glucuronidesvia UGT2B7Urinemostly conjugates

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 taken by mouth

    peak effect ~2 h

    Codeine usually starts working after half an hour, with maximum effect at two hours, and its effects last about four to six hours.1

  2. hoursliver

    Codeine → morphine, norcodeine and glucuronides

    CYP2D6 → morphineCYP3A4 → norcodeineUGT2B7 → glucuronides

    The liver enzyme CYP2D6 turns codeine into morphine, CYP3A4 makes norcodeine, and UGT2B7 attaches glucuronides to codeine, norcodeine and morphine.1 Its metabolites are far stronger at the μ-opioid receptor than codeine itself, and morphine is about ten times as potent there.1

    Your genes decide the dose you really get: CYP2D6 ultrarapid metabolisers make morphine faster and are at higher risk of morphine toxicity. Poor metabolisers get little effect. CPIC guidelines advise against codeine for both groups.1 The FDA lists age under 12 as a contraindication after deaths in young children, and morphine can pass into breast milk.1
  3. 3–4 hcodeine half-life

    Half the codeine is gone

    plasma half-life 3–4 h

    Codeine's plasma half-life is between 3 and 4 hours. The infobox gives 2.5–3 hours.1 Morphine made from it has a half-life of about 120 minutes.2

    Mixing: TripSit rates opioids with alcohol and opioids with benzodiazepines as Dangerous.3
  4. ~1 dayexit

    Out through the kidneys

    urine, as glucuronides

    Codeine and its metabolites leave mostly through the kidneys, mainly as glucuronide conjugates.1

Sources

  1. Wikipedia, Codeine (pharmacology and infobox), CC BY-SA
  2. Wikipedia, Morphine (pharmacokinetics), CC BY-SA
  3. 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.