Drug interactions
Efavirenz + Sofosbuvir / velpatasvir
Severity: Major
Efavirenz and Sofosbuvir / velpatasvir: major 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 lowers velpatasvir exposure, and may reduce sofosbuvir exposure as well. This can lead to reduced antiviral activity and a risk of hepatitis C treatment failure. The combination is not recommended according to product labeling.
What this interaction means in plain words
Efavirenz and Sofosbuvir / velpatasvir can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for.
Why it happens
Efavirenz induces CYP2B6, CYP2C8 and CYP3A4 (and possibly P-gp), increasing the metabolism of velpatasvir.
What to do
Avoid the combination and switch the HIV regimen to a non-inducing option such as an integrase inhibitor-based regimen before starting sofosbuvir/velpatasvir. If this is not possible, choose a different HCV regimen after specialist advice.
What to ask your pharmacist
- Does the benefit of taking both outweigh the risk in my case?
- Do I need any blood test, ECG or other check while on both?
- What early warning signs should I watch for, and what should I do if they appear?
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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
Frequently asked questions
Can I take Efavirenz with Sofosbuvir / velpatasvir?
MediHelp rates the interaction as major. Efavirenz and Sofosbuvir / velpatasvir can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for. Efavirenz lowers velpatasvir exposure, and may reduce sofosbuvir exposure as well. This can lead to reduced antiviral activity and a risk of hepatitis C treatment failure. The combination is not recommended according to product labeling.
How serious is the interaction between Efavirenz and Sofosbuvir / velpatasvir?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Avoid the combination and switch the HIV regimen to a non-inducing option such as an integrase inhibitor-based regimen before starting sofosbuvir/velpatasvir. If this is not possible, choose a different HCV regimen after specialist advice.
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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