Agents that act luminally to treat diarrhoea and constipation.

Diarrhoea and constipation are common clinical complaints that negatively affect quality of life, reduce work productivity and lead to considerable health-care expenditure. A variety of therapies have been used to treat these conditions. Unlike drugs that require systemic absorption to exert their effects, luminally acting agents improve diarrhoea and constipation by altering intestinal and/or colonic motility, as well as mucosal absorption and secretion, through a variety of mechanisms. Examples of luminally acting agents for diarrhoea include peripherally acting opiate analogues, enkephalinase inhibitors, bile-acid binding agents, nonabsorbed antibiotics, probiotics, bismuth-containing compounds, berberine and agents with possible effects on intestinal secretion or permeability. Luminally acting drugs for constipation include bulking agents, surfactants, osmotics, stimulants, chloride-channel activators, probiotics, drugs that increase delivery of bile acids to the colon and natural therapies such as prunes and hemp seed extract. As the physiological effects of luminally acting drugs are largely confined to the gastrointestinal tract, these agents are unlikely to cause adverse effects outside of the gastrointestinal tract.