Lomotil Dosing for Diarrhea
The recommended adult dose of Lomotil (diphenoxylate-atropine) is 2 tablets (5 mg diphenoxylate) four times daily initially (20 mg/day total), reduced to maintenance of 2 tablets daily once control is achieved, though loperamide is strongly preferred as first-line therapy due to superior efficacy and safety profile. 1
Why Lomotil Is Not First-Line
Loperamide should be used instead of Lomotil for acute diarrhea management. 2, 3 The American Gastroenterological Association recommends loperamide as first-line treatment because:
- Lomotil is generally less effective than loperamide for acute diarrhea 2
- Lomotil causes more central nervous system effects (sedation, dizziness) 2, 4
- Lomotil has more peripheral anticholinergic side effects from the atropine component (dry mouth, blurred vision, urinary retention) 2, 4
- Lomotil requires a prescription while loperamide is available over-the-counter 5
FDA-Approved Lomotil Dosing
Adults
- Initial dose: 2 tablets (5 mg diphenoxylate) four times daily (20 mg/day total) 1
- Maintenance: Reduce to as little as 2 tablets daily once control achieved 1
- Duration: Clinical improvement should occur within 48 hours for acute diarrhea 1
- Chronic diarrhea: If no improvement after 10 days at maximum dose (20 mg/day), further treatment unlikely to help 1
Children
- Under 2 years: Contraindicated - do not use 1
- Ages 2-13 years: Use only oral solution (not tablets), with special caution 1
- Dosing: 0.3 mg/kg/day has been studied, though not recommended as first-line 6
Critical Safety Contraindications
Never use Lomotil in these situations: 3, 5
- Severe dysentery with high fever or bloody stools 3
- Suspected infectious diarrhea from invasive organisms (Shigella, Salmonella, STEC) 3, 5
- Children under 2 years of age 1
The risk with invasive organisms is prolonged illness and toxic complications, as documented in a case of Shiga dysentery where Lomotil use led to a two-year course of intermittent diarrhea 7.
Preferred Alternative: Loperamide Dosing
For acute diarrhea, use loperamide instead: 8
- Initial dose: 4 mg (2 tablets) 8
- Maintenance: 2 mg after each unformed stool or every 2-4 hours 8
- Maximum: 16 mg per day 8
- Onset: Takes 1-2 hours to reach therapeutic effect 8
When Lomotil Might Be Considered
Lomotil is listed as a third-line option only after loperamide and octreotide have failed in cancer patients with therapy-associated diarrhea, and only after excluding infectious causes 3. In chronic diarrhea with fecal incontinence, Lomotil reduced stool frequency from 4.9 to 2.6 times/day and stool weight from 460 to 256 g/day 9.
Common Pitfalls to Avoid
- Do not use in bloody diarrhea or high fever - this suggests invasive infection where antimotility agents can worsen outcomes 3, 5
- Do not confuse with paregoric - these are different formulations with different dosing 8
- Monitor for paralytic ileus - rare but serious complication with high-dose use 8
- Avoid in neutropenic patients - requires careful risk-benefit assessment 3