Phosphodiesterase type 5 inhibitor sildenafil citrate does not potentiate the vasodilative properties of nebivolol in rat aorta

BackgroundSildenafil citrate (SIL) is contraindicated in patients with coronary heart disease who are treated with nitric oxide (NO) donators such as organic nitrates, as it potentiates NO-mediated vasodilation. The present study investigated whether SIL also affects the vasodilatory effects of nebivolol (NEB), a selective β1-adrenoceptor blocker with an additional, endothelium-dependent NO-liberating property, in comparison to the combination SIL/glycerol trinitrate (GTN).Methods and resultsExperiments were performed in isolated vessel rings of rat aorta (Wistar rats, 8–12 weeks), which had been pre-contracted with phenylephrine (10− 5 M). Isometric tension was measured by a force transducer, and cumulative concentration–response curves were obtained for each drug. The rank order of vasodilatory potency as measured by the concentration needed to achieve 50% relaxation (EC50) was GTN (0.08 μM) > SIL (1.25 μM) ≥ NEB (3.5 μM). In the presence of both therapeutic (1 nM) and high (1 μM) concentrations of SIL, vasodilation of GTN was potentiated as indicated by a significant increase in vasodilatory potency (EC50 GTN + low SIL: 0.019 μM, EC50 GTN + high SIL: 0.002 μM; both P < 0.01 vs. GTN). In contrast, SIL did not potentiate the vasodilatory effect of NEB (EC50 NEB + low SIL: 5.01 μM, EC50 NEB + high SIL: 3.2 μM; n.s. vs. NEB).ConclusionsThese data demonstrate that SIL does not potentiate NEB-induced vasodilation in vitro. These findings indicate that the interaction between SIL and NO-donators/organic nitrates does not apply to the NO-liberating properties of NEB. Our findings suggest that SIL may safely be used in hypertensive patients treated with NEB.