sitaxsentan + tadalafil

This is a **combination therapy** of sitaxsentan, a selective endothelin receptor antagonist, and tadalafil, a phosphodiesterase type 5 (PDE5) inhibitor. Both drugs act as vasodilators but through different pathways: sitaxsentan selectively blocks endothelin-1 at the ETA receptor preventing vasoconstriction and vascular proliferation, while tadalafil inhibits PDE5, leading to increased cGMP and relaxation of pulmonary vascular smooth muscle. This combination has been reported in case series for the treatment of **idiopathic pulmonary arterial hypertension (iPAH)** in patients who have relapsed or not tolerated other therapies. Clinical experience suggests the combination leads to improved symptoms and hemodynamics without observed combination-related adverse effects.