Drug interactions
Efavirenz + Levonorgestrel
Severity: Major
Efavirenz and Levonorgestrel: 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 can lower levonorgestrel concentrations and reduce contraceptive efficacy, including with emergency contraception. This raises the risk of unintended pregnancy.
What this interaction means in plain words
Efavirenz and Levonorgestrel 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 belongs to Anti Virals; Levonorgestrel belongs to Endocrine.
Why it happens
CYP3A4 induction by efavirenz increases levonorgestrel clearance.
What to do
For emergency contraception, consider a copper IUD or a higher levonorgestrel dose per local guidance. For ongoing contraception, add a barrier method or use a non-interacting method.
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
Other interactions of Levonorgestrel
Frequently asked questions
Can I take Efavirenz with Levonorgestrel?
MediHelp rates the interaction as major. Efavirenz and Levonorgestrel 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 can lower levonorgestrel concentrations and reduce contraceptive efficacy, including with emergency contraception. This raises the risk of unintended pregnancy.
How serious is the interaction between Efavirenz and Levonorgestrel?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: For emergency contraception, consider a copper IUD or a higher levonorgestrel dose per local guidance. For ongoing contraception, add a barrier method or use a non-interacting method.
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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