Drug interactions
Efavirenz + Saquinavir
Severity: Major
Efavirenz and Saquinavir: 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 saquinavir concentrations when it is not boosted, and both drugs can prolong the QT interval. This combination risks virologic failure and arrhythmia.
What this interaction means in plain words
Efavirenz and Saquinavir 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
CYP3A4 induction by efavirenz reduces saquinavir levels, with additive QT prolongation.
What to do
Do not use saquinavir with efavirenz unless ritonavir-boosted, and then obtain a baseline ECG. Monitor ECG and viral load.
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 Saquinavir?
MediHelp rates the interaction as major. Efavirenz and Saquinavir 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 saquinavir concentrations when it is not boosted, and both drugs can prolong the QT interval. This combination risks virologic failure and arrhythmia.
How serious is the interaction between Efavirenz and Saquinavir?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Do not use saquinavir with efavirenz unless ritonavir-boosted, and then obtain a baseline ECG. Monitor ECG and viral load.
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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