Major
Ketoconazole × Tamsulosin
Systemic antimycotics. Imidazole derivatives×Alpha-adrenergic blockers for prostatic disorders
Mechanism
Ketoconazole is a potent CYP3A4 inhibitor – the main tamsulosin metabolic route. Tamsulosin plasma levels rise 2- to 3-fold; orthostatic hypotension and syncope emerge.
Symptoms
Sudden blood pressure drop on standing, syncope, dizziness. Older patients: fall and fracture risk.
Management
Avoid the combination. Alternative antifungals: terbinafine for dermatophytosis or echinocandins for systemic mycoses. Alternative for benign prostatic hyperplasia: a 5α-reductase inhibitor (finasteride, dutasteride).
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.