Drug interactions
Codeine + Quinidine
Severity: Moderate
Codeine and Quinidine: moderate interaction.
Last updated
For healthcare professionals — reference only. This page is a brief summary, not medical advice and not a substitute for official labeling or clinical judgement. Always verify before prescribing or dispensing.
Summary
Quinidine is a very potent CYP2D6 inhibitor and almost completely blocks the formation of morphine from codeine. Codeine then provides little or no analgesia, effectively acting as a pharmacologic poor metabolizer state.
What this interaction means in plain words
Codeine and Quinidine can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken.
Codeine belongs to Musculoskeletal; Quinidine belongs to Anti Parasitic.
Why it happens
Quinidine strongly inhibits CYP2D6, preventing O-demethylation of codeine to morphine.
What to do
Avoid relying on codeine for pain in patients taking quinidine and choose a non-CYP2D6-dependent analgesic such as morphine. Do not escalate the codeine dose to compensate.
What to ask your pharmacist
- Should I take them at different times of day?
- Does the dose of either medicine need to change?
- Is there anything I should avoid, such as alcohol or certain foods, while on both?
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Other interactions of Codeine
- Alvimopan + Codeine Contraindicated
- Codeine + Isocarboxazid Contraindicated
- Codeine + Olanzapine / samidorphan Contraindicated
- Codeine + Phenelzine Contraindicated
- Codeine + Tranylcypromine Contraindicated
- Alfentanil + Codeine Major
Other interactions of Quinidine
- Adagrasib + Quinidine Contraindicated
- Arsenic trioxide + Quinidine Contraindicated
- Artemether / lumefantrine + Quinidine Contraindicated
- Chloroquine + Quinidine Contraindicated
- Dofetilide + Quinidine Contraindicated
- Dronedarone + Quinidine Contraindicated
Frequently asked questions
Can I take Codeine with Quinidine?
MediHelp rates the interaction as moderate. Codeine and Quinidine can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken. Quinidine is a very potent CYP2D6 inhibitor and almost completely blocks the formation of morphine from codeine. Codeine then provides little or no analgesia, effectively acting as a pharmacologic poor metabolizer state.
How serious is the interaction between Codeine and Quinidine?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Avoid relying on codeine for pain in patients taking quinidine and choose a non-CYP2D6-dependent analgesic such as morphine. Do not escalate the codeine dose to compensate.
What other medicines interact with Codeine?
MediHelp also lists interactions of Codeine with, for example, Alvimopan, Isocarboxazid, Olanzapine / samidorphan. The full list is on the Codeine page.
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