What is the appropriate dose of polyethylene glycol 3350 for a healthy 3‑year‑old child with constipation?

Appropriate PEG 3350 Dose for a 3-Year-Old Child

For a healthy 3-year-old child with constipation, start polyethylene glycol 3350 at 0.8 g/kg/day (approximately 10–12 grams daily for an average-weight child), mixed in at least 4–8 ounces of liquid, and continue for 1–2 weeks before assessing response. 1, 2

Weight-Based Dosing Algorithm

• Initial dose: 0.8–0.88 g/kg/day is the evidence-based starting point for children aged 2–3 years 1, 2
• Effective maintenance dose: Most children respond to 0.7–0.8 g/kg/day after initial treatment 1, 2
• Dose range: Can be adjusted from 0.27 g/kg/day up to 1.42 g/kg/day based on response and tolerability 2
• For a typical 3-year-old weighing 14–15 kg, this translates to approximately 10–12 grams daily as a starting dose 2

Critical Administration Details

• Mix the powder in at least 4–8 ounces of liquid (water, juice, soda, coffee, or tea) 1, 3
• Juices containing sorbitol provide synergistic osmotic benefit and may enhance efficacy 1
• Insufficient liquid volume is the most common cause of treatment failure—ensure the child drinks the full mixture and maintains adequate fluid intake throughout the day 1
• First bowel movement typically occurs within 2–4 days of starting therapy 3

Dose Titration Strategy

• Adjust the dose every 3 days based on stool frequency and consistency to achieve approximately 2 soft stools per day 2
• If no response after 3–4 days of optimal dosing with confirmed adequate hydration, increase the dose incrementally (e.g., by 0.2 g/kg/day) 1, 2
• If still no bowel movement after 3–4 days, add a bisacodyl suppository (5 mg for children) or glycerin suppository while continuing PEG 1

Treatment Duration and Maintenance

• Continue therapy for 1–2 weeks initially to achieve optimal effect 1, 3
• Average treatment duration in pediatric studies is 6–12 months, with efficacy maintained throughout 1
• Do not stop abruptly once bowel movements normalize—continue maintenance dosing to prevent relapse 1

Safety Profile in Young Children

• PEG 3350 is safe and effective in children as young as 6 months, with a 97.6% success rate in infants and toddlers 4
• Common side effects include mild abdominal distension, flatulence, and transient diarrhea that resolves with dose adjustment 1, 4
• No clinically significant electrolyte disturbances occur with chronic use 5

Critical Pitfalls to Avoid

• Rule out fecal impaction before starting—may require manual disimpaction or enema first 1
• Exclude bowel obstruction or paralytic ileus as contraindications 1
• Ensure adequate daily fluid intake beyond the mixing liquid—PEG requires water to exert its osmotic effect 1
• Do not assume treatment failure without first optimizing dose and confirming compliance with adequate fluid intake 1

When to Escalate Therapy

• If constipation persists despite optimal PEG dosing for 3–4 days, add an oral stimulant laxative (senna 2.5–5 mg daily or bisacodyl 5 mg daily) to exploit complementary mechanisms 1, 5
• Stimulant laxatives work best when given approximately 30 minutes after meals to leverage the gastrocolic reflex 1

FDA Labeling Caveat

Note that the FDA label states "should not be used by children" 3, but this reflects the original over-the-counter approval for adults only. Multiple high-quality pediatric guidelines and research studies strongly support PEG 3350 as first-line therapy for childhood constipation, with extensive safety and efficacy data in children as young as 6 months 1, 4, 2, 6. The American Gastroenterological Association and American Academy of Pediatrics explicitly endorse weight-based dosing for pediatric use 1.