Researchers investigated whether the inhibitory effect of Viagra (sildenafil) is displayed on the musculature of the gastroduodenal tract, and reported their findings in February's Alimentary Pharmacology and Therapeutics.
Sildenafil is already known to effect the smooth muscle cells of corpus cavernosum arterioles by blocking phosphodiesterase-type 5, which inactivates the nitric oxide-stimulated cyclic guanosine monophosphate.
The team recorded antroduodenal motility in 16 normal subjects, by means of a low-compliance manometric system.
Ten minutes after the appearance of a Phase III of the migrating motor complex, a tablet of sildenafil 50 mg, dissolved in 20 ml of water, was infused in the gut of 8 patients. The other 8 subjects received a placebo, randomly and in a double-blind manner. The recording was continued for 90 min.
Antral and duodenal functions in Viagra patients compared to controls:
Wave frequency and amplitude - Lower
Length of Phase I - Longer
Number of Phase III - Lower
Frequency and amplitude of antral and duodenal waves, measured during the first 60 min after infusion, were compared statistically. In addition, the duration of antral and duodenal Phases I, and the number of Phases III occurring during the whole 90 min after infusion, were compared in the two groups.
The group found that antral and duodenal wave frequency and amplitude were significantly lower during the first 60 min after sildenafil administration. Both antral and duodenal Phases I were significantly longer after sildenafil than after placebo, and the number of Phases III which occurred during the 90 min after sildenafil was significantly lower than after placebo.
Professor M.Bortolotti concluded, "Sildenafil inhibits interdigestive motor activity of the antrum and duodenum."