Combination of sitaxentan and tadalafil for idiopathic pulmonary arterial hypertension following relapse on bosentan.

Sitaxentan, a highly-selective endothelin receptor antagonist (ETRA) and bosentan a non-selective ETRA are both approved for the treatment of idiopathic pulmonary arterial hypertension (iPAH). Sildenafil is a phosphodiesterase-5 (PDE-5) inhibitor used in the treatment of iPAH. Tadalafil is a long acting PDE-5 inhibitor largely unexplored for the treatment of iPAH. Following failure of monotherapy combination therapy with an ETRA and a PDE-5 inhibitor is often used, a frequently used combination being bosentan with sildenafil. We report our clinical experience in three patients with iPAH treated with a combination of sitaxentan and tadalafil, who previously discontinued bosentan. There was sustained symptomatic and haemodynamic improvement in all three patients treated with the combination. No adverse effect related to the combination treatment was noted. Sitaxentan and tadalafil, both being once a day treatments, can also possibly increase compliance.