MajorHIV protease inhibitor / pharmacokinetic booster×Alpha-adrenergic blockers for prostatic disorders
Updated · Methodology
Mechanism
Tamsulosin is a CYP3A4 substrate. Ritonavir is a potent CYP3A4 inhibitor. Tamsulosin plasma levels rise 5-fold or more; 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 for benign prostatic hyperplasia on ritonavir: a 5α-reductase inhibitor (finasteride, dutasteride; minimal CYP3A4 dependence) or an α1-blocker with less CYP3A4 dependence (alfuzosin with caution).
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.
Summary of a multi-drug list →
Medicine list: everything you take in one place →
Sources
- FDA: Norvir (ritonavir) prescribing information contraindications (2018)– ; DailyMed setid 2849298e-de6e-47bb-8194-56e075b33fc3
- AEMPS: Ficha técnica: Tamsulosina (nº registro 67308), sección 4.5 (2024)– AEMPS, CIMA, nº registro 67308, sección 4.5