Adverse effects of drugs used in the management of constipation and diarrhoea.

Most laxatives, if used intermittently in the absence of contraindications, are relatively safe. Bulking agents may diminish absorption of some minerals and drugs, but this is not usually clinically significant. Ispaghula can cause serious allergic reactions. The chronic ingestion of stimulant laxatives has been blamed for the development of the 'cathartic colon', but there are no definitive studies which have demonstrated this. Dantron (danthron) preparations should only be used in older patients and the terminally ill because of the risk of hepatotoxicity with this drug. Oral oxyphenisatine should no longer be used. Senna would appear to be the stimulant laxative of choice during pregnancy and lactation. Bisacodyl is the polyphenolic derivative of choice. Lactulose, sorbitol and lactilol rarely cause significant adverse effects. Magnesium salt laxatives and phosphate enemas can cause serious metabolic disturbances in babies and young children. Liquid paraffin is contraindicated if there is any risk of aspiration. Interference with the absorption of fat soluble vitamins would not appear to be clinically significant. Docusate sodium may potentiate the hepatotoxicity of other drugs, but reports of this are rare. The role of cisapride in constipation has not been established. Antidiarrhoeal drugs are second line drugs whose use is aimed at minimising inconvenience and discomfort. No antidiarrhoeals can be recommended for children under 4 years of age. Loperamide is the drug of choice in older children and adults. The atropine component of diphenoxylate/atropine combinations can cause significant adverse effects. Bismuth salicylate is an inconvenient treatment for travellers' diarrhoea as large frequent doses of the liquid formulation are needed. Some bismuth can be absorbed and there is the potential to cause encephalopathy. Octreotide, methysergide and cholestyramine have a role for specific causes of diarrhoea only. Octreotide is effective in high output states from the small or large bowel, with few adverse effects. Clonidine and lidamidine may have a role in the treatment of chronic diabetic diarrhoea. The role of lidamidine in nondiabetic chronic diarrhoea has not been established.