Classification, pharmacology, and side-effects of common laxatives.

No definition of the term laxative is satisfactory since their mode of actions affects multiple mechanisms, absorption/secretion and motor activity. Laxatives are very heterogeneous chemically. They act by either holding water inside the bowel lumen (dietary fibre, osmotic laxatives), by inhibition of water absorption or stimulation of secretion (stimulant laxatives), or by stimulation of colonic motility (stimulant laxatives, 5HT4 agonists). Most laxatives have side-effects but these are usually mild.