Drug interactions
Efavirenz + Simvastatin
Severity: Moderate
Efavirenz and Simvastatin: 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 markedly lowers simvastatin and its active acid exposure, reducing cholesterol-lowering efficacy. Pharmacokinetic studies document this effect.
What this interaction means in plain words
Efavirenz and Simvastatin 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; Simvastatin belongs to Cardiovascular.
Why it happens
Efavirenz induces CYP3A4, increasing first-pass and systemic metabolism of simvastatin.
What to do
Monitor lipid levels and titrate simvastatin per response without exceeding the maximum dose, or switch to a statin less dependent on CYP3A4 such as rosuvastatin or pravastatin.
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?
Pro+ members
Unlock the full page
Create an account and start a Pro+ trial to unlock the full management advice for Efavirenz and Simvastatin, the additional notes, the evidence detail and the whole-prescription interaction checker.
- Full clinical management advice
- Additional notes
- Evidence detail
- Interaction checker for a whole prescription
Try Pro+ free for 14 days on the web. No card needed.
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 Simvastatin
- Atazanavir + Simvastatin Contraindicated
- Clarithromycin + Simvastatin Contraindicated
- Cobicistat + Simvastatin Contraindicated
- Cyclosporine + Simvastatin Contraindicated
- Cyclosporin + Simvastatin Contraindicated
- Danazol + Simvastatin Contraindicated
Frequently asked questions
Can I take Efavirenz with Simvastatin?
MediHelp rates the interaction as moderate. Efavirenz and Simvastatin 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 markedly lowers simvastatin and its active acid exposure, reducing cholesterol-lowering efficacy. Pharmacokinetic studies document this effect.
How serious is the interaction between Efavirenz and Simvastatin?
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 lipid levels and titrate simvastatin per response without exceeding the maximum dose, or switch to a statin less dependent on CYP3A4 such as rosuvastatin or pravastatin.
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.
Full monographs, dosing and an interaction checker in the MediHelp app
Open the complete reference, check multi-drug interactions and use dosing tools in the MediHelp app.
