Studies of the antidiarrheal action of clonidine. Effects on motility and intestinal absorption.

Clonidine, an alpha 2-adrenergic agonist, has been reported to stimulate the rate of electrolyte absorption in vitro, to alter intestinal motility in vivo, and to have antidiarrheal effects in animals. Experiments were performed in 8 healthy volunteers in order to evaluate the antidiarrheal effect of clonidine in humans. When diarrhea was induced by intragastric infusion of 2700 ml of balanced electrolyte solution over 90 min, oral administration of 0.3 mg of clonidine reduced the volume of rectal effluent by 48% (from 1233 +/- 62 to 640 +/- 77 ml, p less than 0.001), a clear-cut antidiarrheal effect. Clonidine increased total gut volume significantly (from 987 +/- 91 to 1830 +/- 142 ml, p less than 0.001), suggesting that clonidine exerted its antidiarrheal effect by altering gut motility, i.e., increasing the capacity of the gut and slowing the transit of fluid through the intestine. In other experiments, the net absorption rate of the whole gut during steady state total gut perfusion was measured. The rate of absorption of fluid was transiently stimulated by clonidine by 15% (from 696 +/- 77 to 799 +/- 55 ml/h, p less than 0.02), indicating an additional effect on mucosal cell function. These studies indicate that in this experimental diarrhea model, clonidine has antidiarrheal properties that are due largely to effects on motility of the gut but that clonidine also modestly stimulates the net rate of absorption by intestinal mucosa.