Major
Clarithromycin × Tamsulosin
Macrolide antibiotic×Alpha-adrenergic blockers for prostatic disorders
Mechanism
Clarithromycin blocks CYP3A4 – the main tamsulosin metabolic route. Tamsulosin plasma levels rise; orthostatic hypotension emerges.
Symptoms
Sudden blood pressure drop on standing, syncope, dizziness. Older patients: fall and fracture risk.
Management
During clarithromycin therapy, halve tamsulosin temporarily or use an alternative: finasteride/dutasteride (minimal CYP3A4 dependence). Alternative antibiotics: azithromycin or doxycycline.
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.