Drug interactions
Codeine + Ritonavir
Severity: Moderate
Codeine and Ritonavir: 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
Ritonavir inhibits CYP2D6 and CYP3A4, which can reduce conversion of codeine to morphine and weaken analgesia. Inhibition of CYP3A4 may also shunt codeine toward norcodeine, and in some situations raise parent opioid exposure, so the net effect is unpredictable.
What this interaction means in plain words
Codeine and Ritonavir 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; Ritonavir belongs to Anti Virals.
Why it happens
Ritonavir inhibits CYP2D6-mediated activation of codeine and CYP3A4-mediated metabolism, altering the balance of metabolites.
What to do
Monitor for loss of analgesia and for opioid toxicity, particularly when ritonavir is started or stopped. Consider a non-CYP2D6-dependent analgesic if pain control is inadequate.
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 Ritonavir
- Alfuzosin + Ritonavir Contraindicated
- Amiodarone + Ritonavir Contraindicated
- Avanafil + Ritonavir Contraindicated
- Colchicine + Ritonavir Contraindicated
- Dronedarone + Ritonavir Contraindicated
- Eletriptan + Ritonavir Contraindicated
Frequently asked questions
Can I take Codeine with Ritonavir?
MediHelp rates the interaction as moderate. Codeine and Ritonavir 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. Ritonavir inhibits CYP2D6 and CYP3A4, which can reduce conversion of codeine to morphine and weaken analgesia. Inhibition of CYP3A4 may also shunt codeine toward norcodeine, and in some situations raise parent opioid exposure, so the net effect is unpredictable.
How serious is the interaction between Codeine and Ritonavir?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Monitor for loss of analgesia and for opioid toxicity, particularly when ritonavir is started or stopped. Consider a non-CYP2D6-dependent analgesic if pain control is inadequate.
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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