Loperamide (Imodium): Overdoses of loperamide associated with risk of serious cardiovascular events

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Loperamide a synthetic opioid inhibits gut motility by binding to opiate receptors in gut wall and reduces gastrointestinal secretions, resulting in improvement in diarrhoea symptoms. Loperamide also increases the tone of the anal sphincter. Loperamide is indicated for the symptomatic treatment of acute diarrhoea. In the UK, loperamide (brand name Imodium) is available on general sale (maximum daily dose 12 mg) and from pharmacists (maximum daily dose 16 mg).

Loperamide taken at high or very high doses as a drug of abuse or for self-treatment of opioid withdrawal may cause serious cardiovascular events such as QT prolongation, torsades de pointes, and cardiac arrest.

A European review of worldwide spontaneous reports identified 19 cases suggestive of cardiac rhythm disorders associated with loperamide abuse and misuse. In all cases, there was evidence of intentional high doses being taken for unapproved indications.

In 13 of the 19 reports, QT prolongation or torsades de pointes were recorded with daily dosages ranging from 40–80 mg up to 800 mg (the recommended maximum daily dose is 16 mg). Of the other 6 reports, one described syncope and irregular heartbeat (daily dose 400–600 mg), one described cardiac arrest with a rhythm of pulseless electrical activity (daily dose 400–800 mg), one described ventricular dysrhythmia (daily dose 400 mg), and one described asystole and death (chronic massive overdose). Two reports did not provide specific information on cardiac rh...