Effects of bisacodyl on ascending colon emptying and overall colonic transit in healthy volunteers

The mechanism of action of bisacodyl in the unprepared human colon remains unclear. Aim To evaluate the effect of oral bisacodyl on the overall and regional colonic transit in humans. Methods In a double-blind, randomized, placebo-controlled study of 25 healthy participants, effects of oral bisacodyl (5 mg p.o. per day) and placebo on colonic transit were compared. A validated scintigraphy method was used to measure colonic transit. The primary transit endpoints, ascending colon emptying t_1/2 and geometric centre of colon isotope at 24 h (overall transit), were compared (Wilcoxon rank sum test). Results There were significant treatment effects on ascending colon t _1/2, with the bisacodyl group demonstrating accelerated emptying [median 6.5 h, interquartile range 5.0-8.0 h] relative to the placebo group [11.0 h (7.0-17.1); P = 0.03]. Numerical differences in colonic geometric centre 24 h [bisacodyl median 3.0 (2.2-3.8), placebo 4.0 (3.1-4.6)] were not significant (P = 0.19). There were no significant differences observed in geometric centre 4 h. Conclusion Oral 5 mg bisacodyl accelerates ascending colon in the unprepared colon in healthy adults; this action may contribute to the drug's efficacy in constipation.