What is the recommended dose of lactulose for a 5-month-old infant?

Lactulose Dosing for a 5-Month-Old Infant

For a 5-month-old infant with constipation, the recommended initial dose of lactulose is 2.5 to 10 mL per day in divided doses, with the goal of producing 2-3 soft stools daily. 1

Pediatric Dosing Guidelines

The FDA-approved dosing for infants is based on achieving therapeutic effect rather than fixed weight-based calculations:

• Initial dose for infants: Start with 2.5 to 10 mL daily in divided doses 1
• Titration principle: Adjust the dose to produce 2-3 soft stools per day 1
• Immediate dose reduction: If diarrhea occurs, reduce the dose immediately; if diarrhea persists, discontinue lactulose 1

Age-Specific Considerations

At 5 months of age, this infant falls into the category where lactulose/lactitol-based medications are specifically authorized and effective:

• Lactulose is approved and effective for infants under 6 months of age for functional constipation 2
• This age group requires careful monitoring as they are more susceptible to dehydration and electrolyte disturbances with excessive dosing 1

Practical Administration Approach

Start conservatively and titrate upward:

• Begin with 2.5 mL once or twice daily (total 2.5-5 mL/day) 1
• Increase gradually every 2-3 days if inadequate response 1
• Maximum range for this age is up to 10 mL daily in divided doses 1
• Split the total daily dose into 2-3 administrations to minimize cramping and improve tolerance 1

Critical Safety Monitoring

Watch for these complications that signal dose reduction is needed:

• Diarrhea (more than 3-4 loose stools daily) requires immediate dose reduction 1
• Dehydration signs (decreased urine output, dry mucous membranes, lethargy) 3
• Excessive gas and abdominal cramping are dose-dependent side effects 4
• Perianal skin irritation from frequent loose stools 4, 3

Common Pitfalls to Avoid

• Do not escalate doses aggressively in infants—the therapeutic window is narrow and excessive dosing causes more harm than benefit 4, 3
• Do not continue lactulose if severe diarrhea develops—this can lead to dangerous dehydration in a 5-month-old 1
• Do not use adult dosing calculations (mL/kg) and extrapolate down—pediatric dosing for infants is specifically lower than weight-based calculations would suggest 1

Alternative Considerations

If lactulose is ineffective or poorly tolerated after appropriate dosing:

• Polyethylene glycol (PEG) is an alternative but is typically reserved for infants over 6 months of age 2, 5
• At 5 months, lactulose remains the first-line osmotic laxative 2
• Investigate underlying causes if constipation persists despite adequate lactulose dosing (dietary factors, anatomical issues, metabolic conditions) 2

Duration of Therapy

• Continue lactulose for as long as needed to maintain regular bowel function 2
• Attempt gradual weaning once regular stool pattern is established for several weeks 2
• Long-term use is generally safe in infants when dosed appropriately 6