Drug interactions
Efavirenz + Mestranol
Severity: Moderate
Efavirenz and Mestranol: 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 may lower exposure to the estrogen, mestranol, which is converted to ethinylestradiol. This could reduce contraceptive effectiveness or cycle control.
What this interaction means in plain words
Efavirenz and Mestranol 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.
Why it happens
Efavirenz induces CYP3A4 and other enzymes, increasing estrogen clearance.
What to do
Recommend an additional or alternative reliable contraceptive method, such as an intrauterine device, while on efavirenz.
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
Frequently asked questions
Can I take Efavirenz with Mestranol?
MediHelp rates the interaction as moderate. Efavirenz and Mestranol 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 may lower exposure to the estrogen, mestranol, which is converted to ethinylestradiol. This could reduce contraceptive effectiveness or cycle control.
How serious is the interaction between Efavirenz and Mestranol?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Recommend an additional or alternative reliable contraceptive method, such as an intrauterine device, while on efavirenz.
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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