Bisacodyl (Dulcolax) belongs to the same therapeutic class as sennosides (a stimulant laxative that acts on the intestinal wall to promote motility and bowel movement). The onset of action for bisacodyl tablets is approximately 10―12 hrs, and the bisacodyl suppository is approximately 15 minutes. If you are using the tablets, use a similar approach as for sennosides.

Reference

Twycross R, Wilcock A, Dean M. Canadian Palliative Care Formulary, 1st Canadian ed. Nottingham, UK: Palliativedrugs.com; 2010.