Drug interactions
Efavirenz + Gefitinib
Severity: Moderate
Efavirenz and Gefitinib: 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, which is the main route of gefitinib metabolism. Gefitinib exposure falls and the antitumor effect may be reduced.
What this interaction means in plain words
Efavirenz and Gefitinib 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; Gefitinib belongs to Oncology.
Why it happens
CYP3A4 induction by efavirenz increases gefitinib clearance.
What to do
Consider increasing gefitinib to 500 mg daily with close monitoring of tolerability, and return to 250 mg about 7 days after efavirenz is stopped. Alternatively choose a non-inducing antiretroviral.
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 Gefitinib
Frequently asked questions
Can I take Efavirenz with Gefitinib?
MediHelp rates the interaction as moderate. Efavirenz and Gefitinib 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, which is the main route of gefitinib metabolism. Gefitinib exposure falls and the antitumor effect may be reduced.
How serious is the interaction between Efavirenz and Gefitinib?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Consider increasing gefitinib to 500 mg daily with close monitoring of tolerability, and return to 250 mg about 7 days after efavirenz is stopped. Alternatively choose a non-inducing antiretroviral.
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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