The inhibitory effect of 15(R)15 methyl prostaglandin E2 and the interaction with atropine on stimulated gastric acid secretion in man.

The inhibitory effect of 15(R)15 methyl prostaglandin E2 (Me PGE2) on the gastric acid response to pentagastrin stimulation, 0.6 micrograms.kg-1.h-1, was examined in healthy male volunteers. Each subject underwent a control test and tests with intragastrically administered graded doses of 15(R)15 Me PGE2 as free acid (80, 140, 200, and 400 micrograms, n = 5) and as methylester (80, 140, and 200 micrograms, n = 6). The percentage inhibition of the acid output during 2 h after increasing doses of the free acid was 24 +/- 11, 49 +/- 7, 44+/-9, and 76 +/- 12%. Corresponding figures for the methylester were 35 +/- 2, 54 +/- 5, and 64 +/- 8%. Both volume and acidity were reduced. Side effects did not occur, except for moderate diarrhoea in one subject after 400 micrograms of the free acid. In a third series (n = 6) the combined effect of 80 micrograms methyl ester (44 +/- 5% inhibition) and 1.5 mg atropine sulphate was studied. Atropine alone gave a 43 +/- 6% inhibition by lowering the secreted volumes. For the combination the inhibition was 82 +/- 3%. Intragastric 15(R)15 Me PGE2 inhibited dose-dependently the pentagastrin-stimulated gastric acid response. Differences between the free acid and methyl ester of the analogue were not significant. Compared with other Me PGE2 compounds, 15(R)15 Me PGE2 was less effective per dose, but the dose range was broader and side effects were slight. Concomitantly given atropine had a significant additive inhibitory effect.