Efavirenz and Voriconazole interaction
Efavirenz and Voriconazole: 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 Voriconazole label · effective 2026-06-02
…and herbal products that induce CYP2C19, CYP2C9, and/or CYP3A4 and for which significantly reduced voriconazole plasma concentrations may be associated with loss of efficacy [see Drug Interactions (7) ]: • Carbamazepine • Efavirenz Concomitant use with efavirenz dosages of 400 mg every 24 hours or higher is contraindicated [see Clinical Pharmacology (12.3) ] .
…clinical studies generally following repeat oral dosing with 200 mg every 12 hours voriconazole to healthy subjects and Rifabutin (CYP450 Induction) Significantly Reduced Contraindicated Efavirenz (400 mg every 24 hours) Results based on in vivo clinical study following repeat oral dosing with 400 mg every 12 hours for 1 day, then 200 mg every 12 hours for at least…
…with 200 mg BID voriconazole to healthy subjects (CYP3A4 Inhibition) Significantly Increased Contraindicated Rifabutin (CYP3A4 Inhibition) Significantly Increased Contraindicated Efavirenz (400 mg every 24 hours) Results based on in vivo clinical study following repeat oral dosing with 400 mg every 12 hours for 1 day, then 200 mg every 12 hours for at least…
A Voriconazole-Efavirenz Drug Interaction Study Demonstrated the Potential for the Metabolism of Voriconazole to be Induced by Efavirenz and Other NNRTIs (Decreased Plasma Exposure) Careful assessment of voriconazole effectiveness.
Other NNRTIs Non-Nucleoside Reverse Transcriptase Inhibitors (CYP3A4 Inhibition) A Voriconazole-Efavirenz Drug Interaction Study Demonstrated the Potential for Voriconazole to Inhibit Metabolism of Other NNRTIs (Increased Plasma Exposure) Frequent monitoring for adverse reactions and toxicity related to NNRTI.
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.
When voriconazole is coadministered with efavirenz, voriconazole maintenance dose should be increased to 400 mg every 12 hours and efavirenz dose should be decreased to 300 mg once daily using the capsule formulation.
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.
Consider alternative antifungal treatment because no dose recommendation for ketoconazole can be made.
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.