Effects of phenylpropanolamine on gastric retention in the adult rat.

Phenylpropanolamine (PPA) induces anorexia and weight loss via an as yet unidentified mechanism. In the present study, we evaluated the inhibitory action of PPA on gastric emptying. Adult female Sprague-Dawley rats consumed a wet-mash test meal and were then treated (IP) with either saline or 5, 10, 20 or 40 mg/kg PPA. Gastric retention (ratio of weight of gastric content to weight of mash consumed) was evaluated immediately after the meal in a group of saline-treated rats or 3 hours after the meal in the drug groups and another saline-treated group. Rats treated with saline exhibited minimal retention (0.21) over a 3 hour period whereas rats treated with 5, 10, 20 or 40 mg/kg dl-PPA exhibited increased gastric retention ratios of 0.29, 0.66, 0.63, and 1.38, respectively. These data demonstrate that PPA has a marked inhibitory action on gastric emptying and suggest that further studies are warranted to evaluate the possible contribution of gastric retention to the anorexic action of PPA.