Influence of antacids on the gastric antisecretory activity of the synthetic prostanoid (8R,11R,12S,15R,5Z,13E)-15-(acetyloxy)- 11,16,16-trimethyl-9-oxoprosta-5,13-dien-1-oic acid in dogs.

Liquid antacids that contain aluminum-magnesium hydroxides reduce the absorption of various therapeutic agents. To assess the potential for such an interaction with the synthetic anti-ulcer prostanoid (8R,11R,12S,15R,5Z,13E)-15-(acetyloxy)-11, 16,16-trimethyl-9-oxoprosta-5,13-dien-1-oic acid (1; Ro 22-6923), we studied the effect of Mylanta and DiGel liquid on the gastric antisecretory activity of this drug in dogs. Dogs were prepared with a modified Pavlov (innervated) pouch. Compound 1 was administered alone or with liquid antacid into the main stomach while acid secretion into the pouch was measured. Mylanta (30 mL) and DiGel (35 mL) failed to significantly reduce the ability of 1 (0.5 mg/kg, orally) to inhibit histamine (25 micrograms/kg/h)-stimulated secretion. Neither the onset nor the duration of action of 1 was affected by either antacid. The total acid output over the 4 h after administration of 1 was not significantly affected by the antacids. The results suggest that Mylanta and DiGel, or antacids of a composition similar to that of these products are not likely to interfere with the antisecretory activity of 1 in humans.