What is the maximum daily dosage of Lomotil (diphenoxylate) that should not be exceeded?

Maximum Daily Dosage of Lomotil (Diphenoxylate)

The maximum daily dose of Lomotil should not exceed 20 mg of diphenoxylate (8 tablets) in adults, and clinical improvement should be evident within 48 hours for acute diarrhea or 10 days for chronic diarrhea—otherwise, further administration is unlikely to provide benefit. 1

Adult Dosing Guidelines

• Initial dose: 2 tablets four times daily (20 mg diphenoxylate per day) 1
• Maximum dose: 20 mg diphenoxylate per day (8 tablets total) 1
• Maintenance dose: Once control is achieved, reduce to the lowest effective dose—often as little as 5 mg (2 tablets) daily 1

Pediatric Dosing Restrictions

• Contraindicated in children under 2 years of age 1
• Children under 13 years: Use only oral solution, not tablets 1
• Special caution required in young children due to risk of respiratory depression and other serious adverse effects 1

Clinical Decision Points

For acute diarrhea: If no clinical improvement occurs within 48 hours at maximum dosage, discontinue therapy 1

For chronic diarrhea: If no improvement after 10 days at maximum daily dose of 20 mg, symptoms are unlikely to be controlled by continued administration 1

Important Safety Considerations

• Diphenoxylate is inferior to loperamide and codeine for chronic diarrhea management, particularly for controlling urgency and fecal incontinence 2
• Central nervous system side effects are greatest with diphenoxylate compared to alternative antidiarrheal agents 2
• Abuse potential exists: Cases of dependence have been reported with doses ranging from 3 to 250 tablets daily (median 25 tablets), far exceeding recommended dosing 3
• Keep out of reach of children: The atropine component is included specifically to discourage abuse, but overdose can be fatal in children 1

Comparative Efficacy Context

The NCCN guidelines for palliative care recommend loperamide as first-line antidiarrheal therapy (4 mg initially, then 2 mg after each loose stool, up to 16 mg/day maximum), with diphenoxylate/atropine listed as an alternative only for patients not already on opioids at 1-2 tablets every 6 hours PRN, with a maximum of 8 tablets/day 4

Research demonstrates that loperamide and codeine are superior to diphenoxylate for symptomatic treatment of chronic diarrhea, with diphenoxylate being significantly less effective at producing solid stools and more likely to cause problematic central nervous system effects 2

Monitoring Requirements

• Assess nutritional status and degree of dehydration before initiating therapy 1
• Evaluate response within 48 hours for acute diarrhea 1
• Reassess at 10 days for chronic diarrhea—if no improvement, discontinue 1