20 mg bisacodyl for complete bowel evacuation

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2862903/
20 mg bisacodyl

Doses of 10 to 20 mg are given by mouth for complete bowel evacuation, followed by 10 mg as a suppository the next morning.

After both oral and rectal administration in humans, bisacodyl is hydrolyzed by intestinal and bacterial enzymes to a deacetylated active metabolite which is responsible for the laxative action.