Drug interactions
Efavirenz + Nirmatrelvir
Severity: Moderate
Efavirenz and Nirmatrelvir: 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
Nirmatrelvir is only a CYP3A4 inhibitor when boosted with ritonavir, and efavirenz is metabolised mainly by CYP2B6, with CYP2A6 and CYP3A4 playing minor roles. A clinically meaningful rise in efavirenz exposure from nirmatrelvir alone is not expected. Efavirenz, a CYP3A4 inducer, could instead lower nirmatrelvir concentrations.
What this interaction means in plain words
Efavirenz and Nirmatrelvir 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.
Efavirenz belongs to Anti Virals; Nirmatrelvir belongs to Anti Virals.
Why it happens
Efavirenz induces CYP3A4 and may reduce nirmatrelvir exposure; the effect of nirmatrelvir on efavirenz is minimal.
What to do
Nirmatrelvir is given only with ritonavir, so assess the combined regimen. Monitor for reduced antiviral effect.
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 Efavirenz
- Cobimetinib + Efavirenz Contraindicated
- Dienogest / estradiol valerate + Efavirenz Contraindicated
- Dihydroergotamine intranasal + Efavirenz Contraindicated
- Dihydroergotamine + Efavirenz Contraindicated
- Doravirine + Efavirenz Contraindicated
- Efavirenz + Elbasvir / grazoprevir Contraindicated
Other interactions of Nirmatrelvir
- Alfuzosin + Nirmatrelvir Contraindicated
- Amiodarone + Nirmatrelvir Contraindicated
- Apalutamide + Nirmatrelvir Contraindicated
- Carbamazepine + Nirmatrelvir Contraindicated
- Colchicine + Nirmatrelvir Contraindicated
- Dronedarone + Nirmatrelvir Contraindicated
Frequently asked questions
Can I take Efavirenz with Nirmatrelvir?
MediHelp rates the interaction as moderate. Efavirenz and Nirmatrelvir 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. Nirmatrelvir is only a CYP3A4 inhibitor when boosted with ritonavir, and efavirenz is metabolised mainly by CYP2B6, with CYP2A6 and CYP3A4 playing minor roles. A clinically meaningful rise in efavirenz exposure from nirmatrelvir alone is not expected. Efavirenz, a CYP3A4 inducer, could instead lower nirmatrelvir concentrations.
How serious is the interaction between Efavirenz and Nirmatrelvir?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Nirmatrelvir is given only with ritonavir, so assess the combined regimen. Monitor for reduced antiviral effect.
What other medicines interact with Efavirenz?
MediHelp also lists interactions of Efavirenz with, for example, Cobimetinib, Dienogest / estradiol valerate, Dihydroergotamine intranasal. The full list is on the Efavirenz page.
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