Major
Ketoconazole × Rifampicin
Systemic antimycotics. Imidazole derivatives×Antituberculous antibiotic
Mechanism
Dual mechanism. Rifampicin strongly induces CYP3A4, which partly metabolises ketoconazole. Ketoconazole plasma levels fall by 50–80%; antifungal efficacy is lost.
Symptoms
Recurrence of mycosis symptoms: ongoing fever, skin or mucosal lesions; in immunocompromised patients, risk of systemic mycosis progression.
Management
The combination is not prescribed. Alternative antifungal during anti-TB therapy: echinocandins (micafungin, caspofungin; resistant to CYP3A4 induction) or terbinafine for dermatophytosis.
Check the full regimen, not just this pair
Opens the checker with these two drugs prefilled. Add the rest of the regimen and recompute additive risks.