What is the recommended loperamide (Imodium) dosing regimen for acute non‑bloody, non‑febrile diarrhea in adults and children, including over‑the‑counter and prescription limits?

Loperamide Dosing for Acute Non-Bloody, Non-Febrile Diarrhea

For adults and children ≥13 years with acute diarrhea, start with 4 mg (two capsules) immediately, then 2 mg after each unformed stool, not exceeding 16 mg (eight capsules) in 24 hours. 1

Adult Dosing (≥13 Years)

Initial dose: 4 mg (two capsules) followed by 2 mg (one capsule) after each unformed stool 1

Maximum daily dose: 16 mg (eight capsules per day) 2, 1

• Clinical improvement typically occurs within 48 hours 1
• Doses should be spaced 1-2 hours apart to allow therapeutic effect and avoid rebound constipation 3
• Treatment duration for acute diarrhea is generally limited to 48-72 hours 3
• If symptoms worsen or fail to improve within 48 hours, reassess and consider antibiotics, particularly if fever, bloody diarrhea, or severe abdominal pain develops 3

Pediatric Dosing (Ages 2-12 Years)

Ages 2-5 years (13-20 kg): Use liquid formulation (1 mg/5 mL); give 1 mg three times daily on first day (3 mg total) 1

Ages 6-8 years (20-30 kg): 2 mg twice daily on first day (4 mg total) 1

Ages 8-12 years (>30 kg): 2 mg three times daily on first day (6 mg total) 1

After first day: Give 1 mg per 10 kg body weight only after each loose stool, not exceeding first-day maximum 1

Critical Contraindications

Absolute contraindications:

• Children under 2 years of age (risk of respiratory depression and cardiac adverse reactions) 1
• Bloody diarrhea with fever or suspected invasive bacterial infections (Shigella, Salmonella, STEC) 4
• Severe dysentery with high fever 2, 4

Discontinue immediately if:

• Bloody diarrhea develops during treatment 3
• Symptoms worsen after 48 hours 3
• Signs of paralytic ileus appear 2

Over-the-Counter vs. Prescription Limits

Over-the-counter availability: Loperamide is available without prescription for adults 4

Maximum OTC and prescription dose: Both are limited to 16 mg per day for acute diarrhea 1

• Higher doses (up to 24 mg/day) have been used in cancer-related chemotherapy-induced diarrhea, but this exceeds FDA-approved dosing and carries increased cardiac risk 5
• The FDA has warned against exceeding recommended doses due to risk of QT prolongation, torsades de pointes, cardiac arrest, and death 1, 5

Chronic Diarrhea Dosing (If Applicable)

Initial: 4 mg followed by 2 mg after each unformed stool until controlled 1

Maintenance: Average 4-8 mg daily (may be given as single or divided doses) 1

Maximum: 16 mg per day 1

• If no improvement after 10 days at 16 mg/day, further administration unlikely to help 1
• Once-daily dosing is often effective for chronic conditions 6

Monitoring and Safety

Patients should:

• Record number of stools and report fever or dizziness upon standing 3
• Receive appropriate fluid and electrolyte replacement 1
• Be monitored for constipation (most common side effect, especially in females) 3

Avoid in elderly patients taking:

• Class IA or III antiarrhythmics 1
• Other QT-prolonging medications 1

Practical Considerations

• Loperamide has minimal systemic absorption and lacks central opiate effects at therapeutic doses 2, 7
• Superior efficacy compared to diphenoxylate and bismuth subsalicylate 8
• May be combined with antibiotics for moderate-to-severe traveler's diarrhea when appropriate 3
• No dose adjustment needed for renal impairment or elderly patients (though elderly require closer cardiac monitoring) 1