Effects of ranitidine on the enzyme cholinesterase and the rat anococcygeus muscle.

Ranitidine in lower doses, (100 ng and 1 microgram) accelerated the rate of reaction of the enzyme acetylcholinesterase with the substrate acetylthiocholine. However, in higher doses (10 micrograms and 100 micrograms) it inhibited the enzyme activity. In rat anococcygeus muscle preparation, the responses to acetylcholine were significantly inhibited in lower doses whereas in higher doses there was a dose-dependent potentiation of the responses to acetylcholine by ranitidine. The responses to carbachol were however, not affected by ranitidine in the same preparation. Our data suggest cholinomimetic as well as cholinolytic activity of ranitidine.