Effect of sildenafil on gastric emptying in healthy adults

Abstract

Phosphodiesterase type 5 hydrolyzes and inactivates cyclic guanosine monophosphate produced by the nitric oxide-stimulated guanylate cyclase. Sildenafil is a potent, reversible, and highly selective inhibitor of this phosphodiesterase. It causes smooth muscle relaxation by increasing intracellular concentrations of cyclic guanosine monophosphate. The aim of this study was to test the hypothesis that sildenafil alters gastric emptying and the intragastric distribution of food in healthy adults. Nine normal subjects (mean age 28 years, range 25-33) were given a placebo or a tablet of sildenafil (50 mg) at different times along with radio-opaque markers. A gastric emptying scan was used to calculate the t(1/2) for gastric emptying (the time taken for the initial radioactivity to fall by 50%). Intragastric food distribution was also assessed using the gastric emptying scan to calculate proximal gastric emptying t(1/2), the proximal volume (the highest activity value in the proximal stomach at any time point in the study), and the distal volume (the highest activity value in the distal stomach at any time point in the study. Gastric emptying of an indigestible solid meal was assessed by calculating gastric clearance of radio-opaque markers. Sildenafil did not change total gastric emptying or gastric clearance of radio-opaque markers. It shortened the proximal T(1/2), decreased proximal volume, and significantly increased distal volume. Sildenafil alters the intragastric distribution of food rather than causing gastric stasis.