USES: Loperamide is a synthetic opioid medication that is used as an antidiarrheal agent. Because of its ready access and opioid effects, it has become a popular drug of abuse in the United States. PHARMACOLOGY: Loperamide acts directly via opioid receptors on circular and longitudinal intestinal muscles to inhibit peristalsis and prolong transit time. In addition, it causes reduction of fecal volume, increases viscosity, diminishes fluid and electrolyte loss, and shows antisecretory activity. It also increases tone on the anal sphincter.
TOXICOLOGY: The toxicity of loperamide is from its direct action on opioid receptors. In addition, dystonic reactions may develop after toxic doses from the portion of the molecule that is structurally similar to haloperidol.