Efavirenz and Ketoconazole interaction
Efavirenz and Ketoconazole: both prescribing labels flag this combination with the strongest language, such as a contraindication, a boxed warning, or an instruction to avoid it.
Do not combine without a prescriber's guidance. The label language below is the strongest FDA uses.
What the FDA labels say
From the Efavirenz label · effective 2024-03-31
Antifungals: Voriconazole Itraconazole Ketoconazole Posaconazole ↓ voriconazole * ↑ efavirenz * ↓ itraconazole * ↓ hydroxyitraconazole * ↓ ketoconazole ↓ posaconazole * Efavirenz and voriconazole should not be coadministered at standard doses.
Consider alternative antifungal treatment because no dose recommendation for ketoconazole can be made.
QT Prolonging Drugs There is limited information available on the potential for a pharmacodynamic interaction between efavirenz and drugs that prolong the QTc interval.
Consider alternative antifungal treatment because no dose recommendation for itraconazole can be made.
From the Ketoconazole label · effective 2026-07-07
Therefore, administration of potent enzyme inducers of CYP3A4 with ketoconazole tablets is not recommended.
Coadministration of ketoconazole tablets with potent enzyme inducers of CYP3A4 may decrease the bioavailability of ketoconazole to such an extent that efficacy may be reduced.
Taking more than these two? Interactions stack. Check your whole list at once; it stays in your browser.
Open in the checkerNot medical advice. Interaction Checker quotes FDA label text and NIH fact sheets. Whether an interaction matters for you depends on doses, timing, kidney and liver function, and other conditions. Confirm with a pharmacist or prescriber.