What is the difference between bisacodyl and sennosides?

Similar effect. Biscodyl is fairly safe chemical available in tablet, suppository & enema form.Acts directly on colonic nerves to stumulate contractions which lead to mechanical expulsion of stool. Also have effect of increasing fluid & sodium secretion in bowel. Sennosides r derived from senna leaves, available in tablet or liquid form, is converted into bowel contraction stimulant form by colonic bacteria.