What is the pediatric dose of lactulose for constipation?

Pediatric Lactulose Dosing for Constipation

For infants, start with 2.5-10 mL daily in divided doses; for older children and adolescents, use 40-90 mL daily, with the goal of producing 2-3 soft stools per day. 1

Age-Specific Dosing Guidelines

Infants (Under 6 Months)

• Initial dose: 2.5-10 mL daily in divided doses 1
• Lactulose/lactitol-based medications are authorized and effective before 6 months of age 2
• If diarrhea develops, reduce the dose immediately; if diarrhea persists, discontinue lactulose 1

Infants and Young Children (6 Months to 6 Years)

• Start with 1 sachet/day (approximately 6 g lactulose per sachet) 3
• Polyethylene glycol becomes an option after 6 months and may be superior to lactulose 2
• Adjust dose based on response to achieve 2-3 soft stools daily 1

Older Children and Adolescents (6-15 Years)

• Initial dose: 40-90 mL daily (total daily dose) 1
• Can start with 2 sachets/day and titrate as needed 3
• The subjective goal remains producing 2-3 soft stools daily 1

Dose Titration Strategy

Adjust the dose every 1-2 days based on stool frequency and consistency 1:

• If inadequate response after initial dosing, increase gradually
• If diarrhea occurs, reduce dose immediately 1
• Target: 2-3 soft (not watery) bowel movements per day 1

Important Clinical Considerations

Comparative Efficacy

• PEG 3350 demonstrates superior efficacy compared to lactulose in pediatric constipation 3
• In a randomized controlled trial, PEG 3350 achieved 56% success rate versus 29% with lactulose 3
• PEG 3350 causes less abdominal pain, straining, and pain at defecation than lactulose 3
• Consider PEG 3350 as first-line therapy when available, particularly for children over 6 months 3, 2

Common Pitfalls to Avoid

• Bloating and flatulence are dose-dependent side effects that occur in approximately 20% of patients 4, 5
• Primary care physicians tend to undertreat childhood constipation—nearly 40% of children remain symptomatic after 2 months when treated inadequately 6
• Fixed dosing without clear instructions to adjust is a major treatment failure point—only 5% of physicians in one study instructed parents to titrate doses 6

Disimpaction Protocol

• For fecal impaction, use higher initial doses or consider rectal disimpaction first 6, 2
• Children who underwent colonic evacuation followed by daily laxative therapy had significantly better outcomes than those treated less aggressively 6
• After disimpaction, transition to maintenance dosing as outlined above 1

Monitoring and Side Effects

• Watch for excessive diarrhea, which can lead to hypokalemia and hypernatremia 4
• Monitor for abdominal pain and bloating, which may require dose reduction 4
• Treatment duration should be sufficient—typically months, not weeks—to prevent relapse 1, 2

When Lactulose May Not Be Optimal

• Lactulose has very low certainty of evidence even in adults 7
• In pediatric populations, PEG 3350 at 0.26 g/kg provided better success with fewer side effects compared to lactulose at 0.66 g/kg 3
• For infants under 18 months, PEG 3350 at 0.78 g/kg/day is safe and effective with 97.6% response rate 8