Superior vasodilation of human pulmonary vessels by vardenafil compared with tadalafil and sildenafil: additive effects of bosentan.

OBJECTIVES: Pulmonary arterial hypertension is characterized by pulmonary vascular proliferation and remodelling, leading to a progressive increase in pulmonary arterial resistance. Vasodilator properties of 3 different phosphodiesterase (PDE)-5 inhibitors alone and in combination with an endothelin (ET) receptor antagonist were compared in an ex vivo model.

METHODS: Segments of human pulmonary arteries (PAs) and pulmonary veins (PVs) were harvested from lobectomy specimens. Contractile forces were determined in an organ bath. Vessels were constricted with norepinephrine (NE) to determine the effects of sildenafil, tadalafil and vardenafil and with ET-1 to assess the effects of bosentan.

RESULTS: All 3 PDE-5 inhibitors had no relevant effect on the basal tone of the vessels. Both sildenafil and vardenafil significantly (P < 0.0001) reduced the responses of the vessels to NE, whereas tadalafil was effective only in PA (P = 0.0009) but not in PV (P = 0.097). Sildenafil relaxed NE-preconstricted PV (P < 0.0001) but not PA (P = 0.143). Both tadalafil and vardenafil relaxed PA and PV significantly. Vardenafil appears to be the most potent of the PDE-5 inhibitors tested. Furthermore, we analysed the combination of bosentan and vardenafil in PA. Bosentan and vardenafil reduced ET-1 and NE induced vasoconstriction stronger than vardenafil alone (P ≤ 0.049).

CONCLUSIONS: Vardenafil caused the most consistent antihypertensive response in this ex vivo model. However, ET receptor antagonism appears to be an even more potent mechanism. A combination therapy using vardenafil and bosentan turned out to be an effective combination to lower vessel tension in PA.