A patient presented with abdominal pain and frequent unsatisfactory bowel movement. For the last one year he has been using a purgative twice weekly to open his bowel. On colonoscopy the colon was found to be atonic with bluish pigmentation of the mucosa. Which is the most likely purgative that the patient has been using

Anthraquinones Lactulose Senna is obtained from leaves and pods of ceain Cassia sp. The glycosides are not active as such. Unabsorbed in the small intestine, they are passed to the colon where bacteria liberate the active anthrol form, which either acts locally or is absorbed into circulation-- excreted in bile to act on small intestine. Thus, they take 6-8 hours to produce action. Taken by lactating mothers, the amount secreted in milk is sufficient to cause purgation in the suckling infant. The active principle of these drugs acts on the myenteric plexus to increase peristalsis and decrease segmentation. They also promote secretion and inhibit salt and water absorption in the colon. adverse effects:- Skin rashes, fixed drug eruption. Regular use for 4-12 months causes colonic atony and mucosal pigmentation (melanosis). Ref:- kd tripathi; pg num:-674,675