Sildenafil citrate potentiates the hypotensive effects of nitric oxide donor drugs in male patients with stable angina

OBJECTIVE We sought to study the effects of a single oral dose of sildenafi l citrate (50 mg) on blood pressure (BP) in men taking the nitric oxide (NO ) donor drugs isosorbide mononitrate (ISMN) or glyceryl trinitrate (GTN) fo r stable angina. BACKGROUND Sildenafil, a selective phosphodiesterase type 5 inhibitor, is a n orally effective treatment for erectile dysfunction. The presence of phos phodiesterases in the vasculature suggests the possibility of an interactio n between sildenafil and NO donor drugs. METHODS Two double-blind, placebo-controlled, randomized, two-way crossover trials were undertaken. Sixteen male patients received oral ISMN (20 mg tw ice a day) for five to seven days before their dose of sildenafil or placeb o and continued receiving ISMN daily until administration of the alternate drug seven days later. For the second study, 15 male patients received subl ingual GTN (500 mu g) 1 h after sildenafil or placebo on each of two study days, which were seven days apart. Sitting or standing BP was measured befo re and for 6 h after the administration of the study drug. RESULTS The effects of sildenafil plus ISMN on BP (standing mean maximum re ductions from baseline in systolic/diastolic BP, -52/-29 mm Hg) were greate r than the effects of placebo plus ISMN on BP (-25/-15 mm Hg; p < 0.001). S ildenafil plus GTN also resulted in greater sitting mean maximum reductions from baseline in systolic/diastolic BP (-36/-21 mm Hg) compared with place bo plus GTN (-26/-12 mm Hg, p < 0.01). CONCLUSION Coadministration of sildenafil with ISMN or GTN produced signifi cantly greater reductions in Br than ISMN or GTN alone. Based on these data , sildenafil should not be administered to patients taking nitrates. (J Am Coil Cardiol 2000;36:25-31) (C) 2000 by the American College of Cardiology.