Rioprostil heals pre-existing aspirin-induced gastric lesions in dogs during daily aspirin administration without altering the anti-inflammatory or analgesic efficacy of aspirin.

Rioprostil (3-100 micrograms/kg/day p.o.), but not cimetidine (30 mg/kg/day p.o.), healed pre-existing aspirin (1950 mg)-induced gastric lesions in dogs despite daily aspirin (975 mg) administration. Gastric antisecretory doses of rioprostil (10 and 100 micrograms/kg/day) decreased lesion scores by 71 to 77 and 90 to 93% after 7 and 11 days, respectively. A nonantisecretory dose of rioprostil (3 micrograms/kg/day) decreased lesion scores by 80% after 14 days. In contrast, lesion scores in dogs receiving either vehicle or a maximal gastric antisecretory dose of cimetidine (30 mg/kg/day) remained unchanged during the 28-day course of treatment. In addition, rioprostil prevented the weight loss which accompanied daily administration of aspirin (975 mg) in vehicle- or cimetidine-treated dogs. When cimetidine-treated dogs were switched to daily rioprostil (100 micrograms/kg/day) and aspirin (975 mg/day) therapy, lesions healed within 6 days. In separate studies, rioprostil had no effect on the sensitivity of the gastric mucosa to subsequent aspirin administration. In addition, discontinuation of maintenance therapy during rioprostil treatment was of no increased benefit (i.e., lesions did not heal faster). Finally, in a model of urate-induced knee-joint synovitis, rioprostil treatment did not inhibit the anti-inflammatory or analgesic efficacy of aspirin, or have any proinflammatory effect of its own.