Effect of selective and non-selective antimuscarinics on rectosigmoid motility and gastrointestinal transit

In 12 healthy volunteers, a rectosigmoid motility index (RSMI) was measured when either placebo, 0.5 mg atropine, or 5 mg pirenzepine was given intravenously as a single dose, double-blind, in random order after a control period of 30 min. Compared with the control period, atropine gave a significant decrease of the RSMI during the entire recorded period of 90 min, whereas pirenzepine inhibited RSMI only during the first two 15-min periods. In another series of experiments, gastrointestinal transit was assessed by means of a radiographic marker method. In healthy volunteers, gastrointestinal transit was estimated (n = 20) and gastric secretion was measured (basally and after modified sham feeding; n = 10) during oral medication with placebo, 50 mg pirenzepine twice daily, or 17.5 mg benzilonium bromide twice daily. In 10 of the volunteers gastrointestinal transit was also estimated with 35 mg benzilonium bromide twice daily, and in the other 10 volunteers with 0.6 mg L-hyoscyamine twice daily. The number of retained markers was significantly lower during pirenzepine than during L-hyoscyamine treatment. Neither dose of benzilonium bromide changed the transit of markers. Compared with non-selective antimuscarinics, the effect of pirenzepine was differential: with equipotently acid-reducing doses the decrease of the RSMI after pirenzepine lasted shorter and gastrointestinal transit was accelerated.