Drug interactions
Efavirenz + Ritonavir
Severity: Moderate
Efavirenz 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
Efavirenz induces CYP3A4 and can lower ritonavir exposure, while ritonavir may raise efavirenz levels. Together they have an increased frequency of adverse effects such as dizziness and liver enzyme elevations.
What this interaction means in plain words
Efavirenz 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.
Efavirenz belongs to Anti Virals; Ritonavir belongs to Anti Virals.
Why it happens
Efavirenz induces and ritonavir inhibits CYP3A4, altering the exposure of both drugs.
What to do
Monitor liver enzymes and tolerability, and check the HIV virologic response. Dose adjustments of the protease inhibitor partner are guided by the full regimen.
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 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 Efavirenz with Ritonavir?
MediHelp rates the interaction as moderate. Efavirenz 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. Efavirenz induces CYP3A4 and can lower ritonavir exposure, while ritonavir may raise efavirenz levels. Together they have an increased frequency of adverse effects such as dizziness and liver enzyme elevations.
How serious is the interaction between Efavirenz 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 liver enzymes and tolerability, and check the HIV virologic response. Dose adjustments of the protease inhibitor partner are guided by the full regimen.
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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