A team from Bologna, Italy, investigated the effect of sildenafil (Viagra) on smooth muscle cells of the esophagus.
Sildenafil shows an intense and prolonged inhibitory effect on the smooth muscle cells of corpus cavernosum arterioles. It does this by blocking phosphodiesterase type 5 that inactivates the nitric oxide-stimulated cyclic guanosine monophosphate.
A total of 16 normal subjects (9 men, mean age 34 years) were enrolled in the randomized, double-blind study.
Esophageal motility was recorded by means of a low-compliance manometric system, with side holes for the esophageal body and a sleeve for the lower esophageal sphincter (LES).
After a basal period of 60 min, a tablet of sildenafil 50-mg, ground and dissolved in water, was infused in the stomach in 8 subjects. A placebo tablet was infused into the other 8 subjects. The recording continued for another 60 min.
LES tone and postdeglutitive residual pressure, as well as amplitude, propagation velocity, and onset latency of contractions were measured each minute. The values were averaged every 5 min, and the mean of the entire basal and postinfusion periods was calculated.
The postinfusion values were compared with the basal values in each group and with the corresponding values of the other groups.
| Sildenafil's inhibitory effect lasted for 1 hour after infusion.
| Digestive Diseases and Sciences |
The percent variations of postinfusion values, with respect to basal values, were also compared.
The team found that sildenafil induced a statistically significant decrease of LES tone, residual pressure, wave amplitude, and propagation velocity.
It also induced a significant increase of onset latency of pressure waves, in comparison with the values of the basal period and placebo.
The inhibitory effect reached its maximum 10-15 min after the infusion and lasted about 1 hour.
Mauro Bortolotti concluded on behalf of fellow authors from the University of Bologna, "Sildenafil markedly inhibits the motor activity of the esophageal musculature. It does this by decreasing LES pressure, wave amplitude, and propagation velocity, and increasing the onset latency of pressure waves."