bosentan + tadalafil

Combination of **bosentan**, an endothelin receptor antagonist (ERA), and **tadalafil**, a phosphodiesterase type 5 (PDE5) inhibitor. Both are oral small molecule drugs approved as monotherapy for treatment of **pulmonary arterial hypertension** (PAH). Bosentan blocks endothelin-1 from activating endothelin A and B receptors, resulting in vasodilation and antiproliferative effects. Tadalafil inhibits PDE5, increasing cGMP levels and causing relaxation of pulmonary vascular smooth muscle. This specific combination (bosentan + tadalafil) is studied as combination therapy in PAH to potentially enhance hemodynamic and clinical benefit via complementary pathways.