The effects of rioprostil on gastric emptying and intragastric acidity.

Rioprostil is a 16-methyl-16-hydroxy alcohol analogue of prostaglandin E1 with anti-secretory activity. We have compared the effects of the orally administered drug with those of placebo and of intravenous ranitidine on the rate of gastric emptying of liquids and on the disposal of acid in the stomach, by measuring the response to an intragastrically instilled acid load in 10 healthy male volunteers. The results show that rioprostil significantly increases the rate of gastric emptying compared with placebo and also significantly reduces the recovery of acid from the stomach. Reduction in the amount of intragastric acid was also observed after intravenous administration of ranitidine but the latter drug did not influence the rate of gastric emptying. We conclude that rioprostil, like ranitidine, reduces the amount of acid in the gastric lumen mainly by inhibiting the gastric secretory response to the instilled acid load, while the action of rioprostil on gastric emptying is independent of its gastric antisecretory properties. The combination of pharmacological actions--increasing the rate of gastric emptying of liquids and inhibiting gastric secretion of acid--indicates that rioprostil may be of value in the management of gastro-oesophageal reflux.