Overview
Loperamide is an antidiarrheal medication that acts on opioid receptors in the gut to slow intestinal motility and reduce fluid secretion. It is indicated for symptomatic relief of acute nonspecific diarrhea in patients aged 2 years and older, chronic diarrhea associated with inflammatory bowel disease in adults, and to reduce ileostomy output. The drug carries warnings about serious cardiac adverse reactions, particularly with higher-than-recommended doses.
Mechanism of Action
Loperamide is a synthetic opioid receptor agonist that acts primarily on mu-opioid receptors in the myenteric plexus of the intestinal wall. It inhibits peristalsis by reducing acetylcholine release, decreases intestinal secretions, and enhances water and electrolyte absorption, resulting in reduced stool frequency and improved stool consistency.
Indications
- Control and symptomatic relief of acute nonspecific diarrhea in patients 2 years and older
- Chronic diarrhea in adults associated with inflammatory bowel disease
- Reducing volume of discharge from ileostomies
Common Doses
- 2 mg capsules
- 1 mg/5 mL liquid
Dosage
For acute diarrhea: Initial dose of 4 mg (2 capsules) followed by 2 mg (1 capsule) after each unformed stool, not to exceed 16 mg daily. For chronic diarrhea: Initial dose of 4 mg followed by 2 mg after each unformed stool until controlled, then reduce to maintenance dose of 4-8 mg daily, not to exceed 16 mg daily. Pediatric dosing varies by age and weight.
Contraindications
- Pediatric patients less than 2 years of age
- Known hypersensitivity to loperamide or excipients
- Abdominal pain in the absence of diarrhea
- Acute dysentery with blood in stools and high fever
- Acute ulcerative colitis
- Bacterial enterocolitis caused by Salmonella, Shigella, or Campylobacter
- Pseudomembranous colitis associated with broad-spectrum antibiotics
Side Effects
- Constipation
- Dizziness
- Nausea
- Abdominal pain/cramps
- Dry mouth
- Drowsiness
- Flatulence
- Vomiting
- Rash, pruritus, urticaria
- QT prolongation and serious cardiac arrhythmias (with overdose/misuse)
- Toxic megacolon
- Anaphylactic reactions
Interactions
- CYP3A4 inhibitors (e.g., itraconazole) increase loperamide exposure 3.8-fold
- CYP2C8 inhibitors (e.g., gemfibrozil) increase loperamide exposure 2.2-fold
- P-glycoprotein inhibitors (e.g., quinidine, ritonavir) increase loperamide plasma concentrations 2-3 fold
- Combined CYP3A4 and CYP2C8 inhibitors increase loperamide exposure 12.6-fold
- Loperamide decreases saquinavir exposure by 54%
Counseling Points
- Take only as directed; do not exceed maximum daily dose of 16 mg
- Discontinue if constipation, abdominal distention, or no improvement occurs
- Maintain adequate fluid intake to prevent dehydration
- Seek medical attention if diarrhea persists beyond 48 hours or if fever or blood in stools develops
- Avoid concurrent use with other antidiarrheals
- Store out of reach of children due to risk of serious cardiac events with overdose