Lactulose for Infant Constipation
For infants with constipation, lactulose should be initiated at 2.5-10 mL daily in divided doses, titrated upward based on response with a goal of producing 2-3 soft stools daily, and continued for an adequate duration as constipation often requires prolonged therapy. 1
Initial Dosing Strategy
- Start with 2.5-10 mL daily in divided doses for infants, as specified in the FDA labeling 1
- The lower end of this range (2.5-5 mL daily) is appropriate for younger infants, while older infants approaching 12 months may require doses toward the higher end 1
- Divide the total daily dose into 2-3 administrations to minimize gastrointestinal side effects and improve tolerance 2
Dose Titration Algorithm
- Increase the dose gradually every 2-3 days based on stool frequency and consistency until achieving 2-3 soft, non-forced bowel movements daily 2, 1
- If diarrhea develops at any point, reduce the dose immediately 1
- If diarrhea persists despite dose reduction, discontinue lactulose 1
- Allow 24-48 hours (or occasionally longer) before assessing response and making dose adjustments, as improvement may be delayed 2, 1
Treatment Duration
- Continue lactulose therapy for several months, as functional constipation in infants typically requires prolonged treatment to restore normal colonic motility and prevent relapse 3
- The rule for successful treatment is "sufficient dose for a long time" 3
- Do not discontinue therapy prematurely once symptoms improve, as this commonly leads to recurrence 3
Safety Profile and Monitoring
Common Side Effects
- Bloating, flatulence, and excessive gas occur in approximately 20% of patients and are dose-dependent 2, 4
- Abdominal discomfort and cramping may occur but are difficult to assess in preverbal infants, requiring careful parental observation of feeding behavior, sleep patterns, and crying episodes 2
- These gastrointestinal effects typically improve with dose adjustment 2, 4
Serious Adverse Effects (Rare)
- Excessive dosing can cause diarrhea with potential electrolyte disturbances including hypokalemia and hypernatremia 4
- Monitor for signs of dehydration if diarrhea develops (decreased urine output, dry mucous membranes, lethargy) 4
Practical Considerations
- Lactulose is considered safe, effective, and well-tolerated in constipated children with a favorable safety profile 2
- Adequate hydration is essential while using lactulose 2
- The medication can be mixed with formula, breast milk, or water to improve palatability 2
Position in Treatment Algorithm
- Lactulose is appropriate as first-line osmotic laxative therapy for infants under 6 months of age, as it is specifically authorized and effective in this age group 3
- For infants over 6 months, polyethylene glycol (PEG) becomes an alternative option, though lactulose remains effective and is significantly less expensive 3, 5
- Dietary modifications alone (hyperosmotic mineral water, diet changes) are not effective treatments for established constipation in infants 3
Evidence Quality
The evidence supporting lactulose in infants is limited, with most pediatric data extrapolated from older children and adults 6. However, lactulose has demonstrated effectiveness and safety in clinical practice for decades 7, 5, 8. A 2019 randomized controlled trial in children (using 4-6 mL/kg/day for disimpaction) confirmed lactulose is safe, effective, and well-tolerated, though PEG showed faster response 7. A 1977 controlled trial in children under 15 years found lactulose superior to senna with significantly fewer side effects 8.
Critical Pitfalls to Avoid
- Do not use insufficient doses for inadequate duration, as this is the most common cause of treatment failure 3
- Do not discontinue therapy too early once symptoms improve, as relapse is common 3
- Do not continue lactulose if persistent diarrhea develops despite dose reduction 1
- Do not use in suspected bowel obstruction, as the osmotic mechanism could worsen obstruction 4