What is the dosage and usage of Lomotil (diphenoxylate) for treating diarrhea?

Lomotil (Diphenoxylate-Atropine) for Diarrhea

Direct Recommendation

Lomotil is NOT recommended as a first-line agent for diarrhea—loperamide is superior in efficacy and safety profile, and should be used instead. 1, 2, 3

FDA-Approved Dosing (When Lomotil Must Be Used)

Adults:

• Initial dose: 2 tablets (5 mg diphenoxylate) four times daily (20 mg/day total) 4
• After initial control is achieved, reduce to maintenance dose as low as 5 mg (2 tablets) daily 4
• Maximum daily dose: 20 mg 4
• If no improvement within 48 hours for acute diarrhea or 10 days for chronic diarrhea at maximum dose, discontinue—further treatment unlikely to help 4

Pediatric patients:

• Contraindicated in children under 2 years of age 4
• Ages 2-13 years: Use only oral solution formulation, NOT tablets 4
• Dose: 0.3 mg/kg/day (based on research data) 5
• Must assess nutritional status and degree of dehydration before use 4

Why Loperamide Should Be Used Instead

Loperamide is more effective than Lomotil with fewer side effects:

• Loperamide provides faster symptom control and has longer duration of action than diphenoxylate 3, 6
• Loperamide causes fewer central nervous system effects and peripheral side effects compared to diphenoxylate-atropine 1, 2
• Loperamide is available over-the-counter, while Lomotil requires prescription due to greater abuse potential and central effects 7

Recommended loperamide dosing:

• Initial: 4 mg, then 2 mg after each unformed stool OR every 2-4 hours 8
• Maximum: 16 mg per day 8
• For cancer treatment-induced diarrhea: 2 mg every 2 hours during day and 4 mg every 4 hours at night 7

Critical Safety Contraindications for Both Agents

Never use Lomotil or loperamide in:

• Severe dysentery with high fever or bloody stools 2, 7
• Suspected infectious diarrhea from invasive organisms (Shigella, Salmonella, STEC) 2, 7
• Children under 2 years of age 7, 4

These contraindications exist because antimotility agents can worsen outcomes by prolonging pathogen exposure and increasing risk of toxic megacolon. 2

When Lomotil Might Be Considered (Third-Line)

In cancer patients with chemotherapy-induced diarrhea:

• Only after loperamide has failed 2
• Only after octreotide (100-150 mcg subcutaneously three times daily) has been tried 8, 1
• Only after infectious causes have been excluded 2
• Use with extreme caution in neutropenic patients 2

Mechanism Differences Explaining Inferior Profile

Diphenoxylate-atropine produces more prolonged intestinal transit inhibition than loperamide:

• The combination effect is more pronounced and less titratable 1, 7
• This increases risk of complications in infectious diarrhea by trapping pathogens 7
• Atropine component adds anticholinergic side effects without therapeutic benefit for diarrhea 1

Loperamide has additional antisecretory effects not mediated by opioid receptors, making it more effective for reducing stool volume. 7

Common Pitfalls to Avoid

• Do not use Lomotil as first-line therapy—this is outdated practice that exposes patients to unnecessary risks 1, 2
• Do not combine with activated charcoal—no evidence of benefit and may cause aspiration 7
• Do not continue beyond recommended timeframes if ineffective—48 hours for acute diarrhea, 10 days for chronic at maximum dose 4
• Do not use tablets in children under 13 years—only liquid formulation if absolutely necessary 4