Dulcolax suppositories bisacodyl are ideal for people seeking almost immediate relief from constipation they are reliably effective in 15 to 60 minutes like the tablets the active ingredient in dulcolax suppositories is bisacodyl a proven and safely used medicine because it is effective only in the colon it may be suitable for use during pregnancy but as with all medicines dulcolax suppositories should be avoided in the first trimester unless the expected benefit is thought to out