What are the AAP guidelines for using Miralax (polyethylene glycol) versus glycerin suppository in a 5-month-old infant with constipation?

Management of Constipation in a 5-Month-Old Infant

For a 5-month-old infant who hasn't had a bowel movement in 5 days, glycerin suppositories are the safer first-line option compared to Miralax (polyethylene glycol), as they work locally in the rectum with minimal systemic absorption and provide gentle stimulation.

Assessment of Infant Constipation

Before initiating treatment, consider these key factors:

• Normal stool patterns in infants vary widely - some breastfed infants may go several days without stooling
• Rule out concerning signs such as:
  • Abdominal distension
  • Vomiting
  • Poor feeding
  • Failure to thrive
  • Blood in stool
  • Anal fissures

Treatment Algorithm

First-Line Treatment: Glycerin Suppository

Glycerin suppositories are preferred for infants because:

• They work locally in the rectum without systemic absorption 1
• Produce gentle stimulation of the rectal mucosa
• Help avoid straining
• Typically produce results within 15-60 minutes 2
• Less invasive than other interventions
• Safe for infants

Administration of Glycerin Suppository

1. Use infant-sized glycerin suppository
2. Position infant on back with legs elevated
3. Gently insert the lubricated tip into the rectum
4. Hold buttocks together briefly to prevent expulsion
5. Results typically occur within 15-60 minutes

Second-Line Options

If glycerin suppositories are ineffective:

1. Dietary modifications (if formula-fed):

   • Consider formula with increased magnesium content to soften stool 3
   • Formulas with high β-palmitate may help with constipation 3

2. Polyethylene glycol (Miralax) - use with caution:

   • While PEG has been studied in infants as young as 3 months 4, it is not FDA-approved for children under 2 years
   • If used, the dosage should be carefully calculated at approximately 0.78 g/kg/day 4
   • Monitor closely for side effects including increased gas or transient diarrhea

Important Considerations

• Breastfed infants: Constipation is less common in breastfed infants. If breastfed, do not discontinue breastfeeding in favor of formula 3

• Formula-fed infants: Consider whether recent formula changes might be contributing to constipation

• Fluid intake: Ensure adequate hydration appropriate for age

• Warning signs: If constipation persists despite treatment or if there are signs of obstruction (bilious vomiting, severe distension), urgent evaluation is needed

Follow-up Recommendations

• If the infant responds to treatment, monitor for normal stool patterns
• If constipation recurs, consider underlying causes
• Persistent constipation beyond 2-3 weeks warrants further evaluation for anatomic or functional disorders

Caution

While polyethylene glycol (Miralax) has been studied in infants and found to be effective at a dose of 0.78 g/kg/day 4, it is not FDA-approved for children under 2 years of age 5. Glycerin suppositories represent a safer first-line approach with localized action and minimal systemic effects.