What is the recommended dosage of loperamide (antidiarrheal medication) for treating diarrhea in adults?

Loperamide Dosing for Adult Diarrhea

Start loperamide at 4 mg initially, followed by 2 mg after each unformed stool or every 2-4 hours, with a maximum daily dose of 16 mg. 1, 2

Standard Dosing Algorithm

Initial Dose

• Give 4 mg (two 2 mg capsules) as the loading dose 1, 2

Maintenance Dosing (Choose One Approach)

• 2 mg after each unformed stool (preferred for acute diarrhea) 1, 2
• 2 mg every 2-4 hours (alternative interval-based approach) 1

Maximum Daily Limit

• Never exceed 16 mg (eight 2 mg capsules) per day due to serious cardiac adverse reactions including QT prolongation and Torsades de Pointes 1, 2

Expected Response Timeline

• Loperamide takes 1-2 hours to reach therapeutic effect, so space additional dosing accordingly to avoid rebound constipation 3, 4
• Clinical improvement typically occurs within 48 hours 2
• With combination antibiotic therapy (if indicated), 63% of patients pass no further unformed stools after initial doses, and 91% are well within 24 hours 5

Essential Supportive Measures

• Provide adequate oral fluid and electrolyte replacement 1, 3
• Implement dietary modifications: avoid lactose-containing products (except yogurt and firm cheeses), spices, coffee, and alcohol 1, 3
• Reduce insoluble fiber intake 1

Critical Contraindications and When to Stop

Absolute Contraindications

• Pediatric patients less than 2 years of age (risk of respiratory depression and cardiac adverse reactions) 2
• Grade 3-4 immunotherapy-induced diarrhea (loperamide may worsen outcomes) 1, 3

Clinical Situations Requiring Hospitalization Instead

• Fever with diarrhea 4
• Moderate to severe abdominal pain 4
• Bloody diarrhea 1, 4
• Signs of severe dehydration or sepsis (tachycardia, hypotension) 1

In these scenarios, hospitalize for IV fluids and evaluate for infectious causes (C. difficile, Shigella, other pathogens) rather than relying on loperamide alone 4

Chronic Diarrhea Dosing

• Start with 4 mg followed by 2 mg after each unformed stool until controlled 2
• Once controlled, reduce to maintenance dose of 4-8 mg daily (can be given as single daily dose or divided) 2
• Maximum remains 16 mg per day 2
• If no improvement after 10 days at 16 mg daily, symptoms are unlikely to respond to further loperamide 2

Special Populations

Elderly Patients

• No dose adjustment required, but elderly are more susceptible to QT prolongation 2
• Avoid in elderly taking Class IA or III antiarrhythmics or with risk factors for Torsades de Pointes 2

Hepatic Impairment

• Use with caution as systemic exposure may increase due to reduced metabolism 2

Renal Impairment

• No dose adjustment required (drug mainly excreted in feces) 2

Common Pitfalls to Avoid

• Do not delay initiation—early intervention prevents progression to severe diarrhea 3
• Do not exceed 16 mg daily—supratherapeutic doses cause serious cardiac events 3, 2
• Do not use in severe immunotherapy-induced colitis—worsens outcomes 1, 3
• Do not give additional doses before 1-2 hours have elapsed—prevents rebound constipation 3, 4
• Do not use as monotherapy in infectious dysentery without antibiotics—combination with fluoroquinolones (ciprofloxacin 500 mg twice daily or ofloxacin 400 mg once) is safe and more effective 5, 6

When Loperamide Fails

Refractory Diarrhea Options

• Octreotide 100-150 mcg subcutaneous/IV three times daily, titrate up to 500 mcg three times daily or 25-50 mcg/hour continuous infusion 1, 4
• Oral budesonide 9 mg once daily for chemotherapy-induced diarrhea refractory to loperamide 1
• Bile acid sequestrants (cholestyramine, colestipol, colesevelam) for bile salt malabsorption 1