[Antidiarrheal agents: tools and therapeutic agents]

A host of chemically diverse compounds have antidiarrheal potency, however, only a fraction of these agents has gained clinical acceptance. But regardless of their therapeutic status, the effects of these drugs have enhanced our understanding of the physiology and pathophysiology of the intestinal mucosa. Fluid- and electrolyte substitution are the primary therapeutic measures in severe diarrhea, for that purpose oral rehydration using glucose-sodium solutions has proven simple and effective. In addition gut-selective opiates, for instance loperamide, are indicated. Opiates not only decrease propulsive motor activity of the bowel but also increase intestinal water and electrolyte absorption, both effects are neuronally mediated. Antimicrobial drugs are necessary in only a small fraction of patients with diarrhea. Experimental findings have indicated possible future candidates for treatment of diarrhea: Besides opiates and glucose-electrolyte solutions water and electrolyte absorption is enhanced by alpha 2-adrenergic agents, corticosteroids, and somatostatin. Inhibitors of electrolyte secretion include phenothiazines and opiates, possibly because of binding to calcium-calmodulin, calcium-channel blockers, membrane-stabilizing agents for instance propranolol and inhibitors of prostaglandin-synthesis such as non-steroidal antirheumatic agents.