An Antidiarrhoeal drug is the term used for any drug which provides symptomatic relief for diarrhoea.

Electrolyte solutions are used to replace lost fluids and salts in acute cases. Bulking agents like methylcellulose, guar gum or plant fibre (bran, sterculia, ispaghul etc) are used for diarrhoea in functional bowel disease and to control ileostomy output. Absorbents absorb toxic substances that cause infective diarrhoea, methylcellulose is an absorbent as well. Opiate derivatives slow intestinal transit, but the associated problems make their extended use uncommon.