Antidiarrheal Drugs: Loperamide Overview

Antidiarrheal Drug Overview

• Prototype Drug: Loperamide is the standard antidiarrheal medication.
• Mnemonic for Loperamide: "Dave eLOPEd in Mexico and had travelers diarrhea so he took LOPERamide" helps remember its use.

Loperamide Side Effects

• Common side effects include dizziness, dry mouth, and drowsiness.

Drug Interaction Advisories

• Caution with Antihistamines: Due to increased drowsiness, avoid combining loperamide with antihistamines.
• Quinine Interaction: Patients should not drink tonic water while taking loperamide, as it contains quinine, which can cause QT prolongation when mixed with loperamide.

Pharmacokinetics and Mechanism

• Blood-Brain Barrier: Loperamide does cross the blood-brain barrier but does not cause opioid-like responses in the CNS.
• Mechanism: It is an opioid receptor agonist, specifically binding to mu-opioid receptors in the gut.

Dosing Instructions and Safety

• Dosing Guidance: Initial dose is 2 pills (4mg) after the first loose bowel movement, followed by 2mg after each additional bowel movement.
• Maximum Dose: The maximum recommended dose of loperamide is 8mg within a 24-hour period.

Cardiovascular Considerations

• QT Prolongation: A prolonged QT interval can lead to serious arrhythmias like Torsades de Pointes and potential sudden cardiac death.
• Medication Interactions: Loperamide should not be taken with CNS depressants due to risks of severe drowsiness, and with medications that cause QT prolongation, including specific antiarrhythmics, macrolides, fluoroquinolones, antipsychotics, antidepressants, and antiemetics.