Drug interactions
Efavirenz + Ketoconazole
Severity: Minor
Efavirenz and Ketoconazole: minor 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 is mainly metabolized by CYP2B6 with a minor CYP3A4 contribution, so ketoconazole is expected to cause only a small rise in efavirenz levels. Efavirenz may also lower ketoconazole levels through enzyme induction.
What this interaction means in plain words
Efavirenz and Ketoconazole have a small, usually unimportant interaction. Most people can take both; the pharmacist may still mention it so that any unexpected effect is recognised.
Efavirenz belongs to Anti Virals; Ketoconazole belongs to Anti Fungals.
Why it happens
Ketoconazole weakly inhibits the minor CYP3A4 pathway of efavirenz, while efavirenz may induce CYP3A4.
What to do
No routine dose change is needed; monitor for efavirenz CNS effects and antifungal response.
What to ask your pharmacist
- Is there anything I should notice while taking both?
- Do I need to tell my doctor at the next visit?
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Other interactions of Ketoconazole
- Alfuzosin + Ketoconazole Contraindicated
- Alprazolam + Ketoconazole Contraindicated
- Avanafil + Ketoconazole Contraindicated
- Conivaptan + Ketoconazole Contraindicated
- Dihydroergotamine intranasal + Ketoconazole Contraindicated
- Dihydroergotamine + Ketoconazole Contraindicated
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 Ketoconazole?
MediHelp rates the interaction as minor. Efavirenz and Ketoconazole have a small, usually unimportant interaction. Most people can take both; the pharmacist may still mention it so that any unexpected effect is recognised. Efavirenz is mainly metabolized by CYP2B6 with a minor CYP3A4 contribution, so ketoconazole is expected to cause only a small rise in efavirenz levels. Efavirenz may also lower ketoconazole levels through enzyme induction.
How serious is the interaction between Efavirenz and Ketoconazole?
MediHelp rates it minor, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: No routine dose change is needed; monitor for efavirenz CNS effects and antifungal response.
What other medicines interact with Ketoconazole?
MediHelp also lists interactions of Ketoconazole with, for example, Alfuzosin, Alprazolam, Avanafil. The full list is on the Ketoconazole page.
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