Background: 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.