Senna Leaf fān xiè yè · 番泻叶

Safety. A stimulant laxative, and the most important thing to say about a stimulant laxative is that it is for occasional use. Continuous use produces cramping, watery evacuation, loss of potassium, and — the part people are rarely told — a bowel that stops responding on its own. The older literature calls this the cathartic colon; the modern picture is less dramatic, but laxative dependence is real and slow to reverse. Prolonged use also produces melanosis coli, a harmless brown-black pigmentation of the bowel lining that is noticed at colonoscopy and that frightens people who were not warned about it. It must not be used where the abdomen is acutely painful or obstructed, in appendicitis, in inflammatory bowel disease, or in anyone who is dehydrated. Low potassium is the mechanism behind the interactions: it sensitises the heart to digoxin, it compounds the effect of diuretics and of corticosteroid medicines, and a laxative that hurries the gut along also shortens the time other medicines have to be absorbed. It discolours urine yellow-brown or red, which is harmless and which alarms people. It is not a weight-loss aid: laxatives act below the point where calories are absorbed, so what they remove is water and electrolytes, not fat. In pregnancy and breastfeeding the traditional texts treat it as forbidden or as something to be used only on advice, and the same caution applies to children. One thing it is worth adding, because it is often muddled: unlike aloe latex and cascara, senna was retained as an accepted over-the-counter laxative ingredient when the United States Food and Drug Administration finalised its laxative monograph in 2002 — a regulatory judgement about short-term use, not a licence to take it every day.