What is the recommended dose of lactulose (a laxative medication) for pediatric patients with constipation?

Pediatric Dosing of Lactulose for Constipation

For pediatric constipation, lactulose should be dosed at 1-1.5 g/kg/day (approximately 1.5-2.5 mL/kg/day), divided into 1-2 daily doses, with a maximum of 60 mL/day for most children. 1, 2

Age-Based Dosing Recommendations

• Infants (6 months to 2 years): 2.5-10 mL daily in divided doses 3
• Young children (2-5 years): 5-15 mL daily in divided doses 1, 2
• Older children (6-12 years): 10-20 mL daily in divided doses 1, 3
• Adolescents (>12 years): 15-30 mL daily in divided doses (similar to adult dosing) 1

Administration Guidelines

• Start at the lower end of the dosage range and titrate up based on response 1, 2
• Goal of therapy is to produce 2-3 soft stools daily 1
• If initial dose causes diarrhea, reduce the dose immediately 1
• If diarrhea persists despite dose reduction, discontinue lactulose 1
• For disimpaction therapy in severe cases, higher doses of 4-6 mL/kg/day (maximum 120 mL/day) may be used for up to 6 days 2

Efficacy and Considerations

• Lactulose is an osmotic laxative that works by drawing water into the intestinal lumen and promoting peristalsis 3
• While effective, studies show polyethylene glycol (PEG) has higher success rates compared to lactulose (56% vs 29%) with fewer side effects 4
• Lactulose requires approximately twice the dose compared to PEG for similar efficacy in children (500-750 mg/kg/day vs 250-400 mg/kg/day) 5
• PEG demonstrates better reduction in colonic transit time compared to lactulose (47.6 vs 55.3 hours) 6

Common Side Effects and Monitoring

• Common side effects: Bloating, flatulence, abdominal discomfort, and cramping 3
• Dose-dependent side effects: Higher doses increase risk of gas and abdominal discomfort 3
• Monitoring: Assess stool consistency, frequency, and abdominal symptoms 2
• Palatability: Lactulose has a sweet taste that some children may find unpleasant 4, 5

Special Considerations

• Maintenance therapy should be continued for several months to prevent recurrence of constipation 3
• Lactulose may be used safely in infants, though evidence is limited 1
• For severe constipation with impaction, consider initial disimpaction before starting maintenance therapy 2
• Ensure adequate hydration while using lactulose, as it works by drawing water into the intestine 3

Alternative Options

• If lactulose is ineffective or poorly tolerated, consider PEG 3350 at 0.8-1.0 g/kg/day 7
• For children with significant abdominal pain or bloating on lactulose, PEG may be better tolerated 4
• Stimulant laxatives may be added as rescue therapy for breakthrough constipation 3