What is the recommended dose of polyethylene glycol (PEG) 3350 for an 8-year-old with constipation?

Polyethylene Glycol Dosing for an 8-Year-Old with Constipation

For an 8-year-old child with constipation, start PEG 3350 at 0.4 g/kg/day (approximately 10-12 grams daily for an average 25-30 kg child), mixed in 4-8 ounces of any beverage, given once daily. 1

Evidence-Based Dosing Algorithm

Starting Dose

• Begin with 0.4 g/kg/day as the optimal starting dose based on the highest quality pediatric dose-ranging study, which demonstrated this dose provides the best balance of efficacy and tolerability 1
• For practical administration, this translates to approximately 10-12 grams daily for most 8-year-olds (assuming average weight of 25-30 kg)
• Mix the powder in 4-8 ounces of any beverage—water, juice (prune, pear, apple), or other liquids work equally well 2, 3

Dose Titration Strategy

• Adjust the dose every 3 days based on response, with the goal of achieving 2 soft stools per day 4
• The effective maintenance dose typically ranges from 0.6-0.8 g/kg/day in most children 4, 5
• If the child experiences abdominal pain or fecal incontinence at higher doses, reduce to 0.2-0.4 g/kg/day 1

Expected Response Timeline

• Expect significant improvement within 2 weeks: 73-77% of children achieve ≥3 bowel movements per week at doses of 0.2-0.8 g/kg/day 1
• Stool frequency typically increases from 2-3 per week to 7 per week within the first treatment period 5
• Encopresis (if present) decreases significantly, from approximately 10 episodes per week to 1-3 episodes per week 4, 5

Critical Implementation Details

Mixing and Administration

• Ensure complete dissolution before drinking—do not allow the child to drink if clumps remain visible 3
• Adequate overall fluid intake throughout the day is essential for PEG to work effectively, not just the mixing liquid 2
• The powder can be mixed in cold, hot, or room temperature beverages 3
• Juices with sorbitol content (prune, pear, apple) may provide synergistic benefits due to their own osmotic effects 2

Duration of Therapy

• FDA labeling states "do not use more than 7 days" for children 16 years and under without physician guidance 3
• However, research demonstrates safety and efficacy for much longer durations: mean treatment duration of 6.2 months in infants and up to 21 months in some cases 6
• Continue maintenance therapy as long as needed, as constipation often requires prolonged treatment 4, 7

Common Pitfalls and How to Avoid Them

Insufficient Dosing

• Do not assume treatment failure without confirming adequate dosing and fluid intake—many families use insufficient liquid volume or inadequate daily hydration 8
• If no response after 3-4 days at 0.4 g/kg/day, increase the dose rather than abandoning PEG 1, 4

Side Effects Management

• Transient diarrhea occurs in some children but typically resolves with dose adjustment—reduce by 25-50% if this occurs 6, 1
• At doses of 0.8 g/kg/day, increased abdominal pain and fecal incontinence may occur; use 0.4 g/kg/day as the preferred starting point to minimize this 1
• The medication is generally well-tolerated with minimal adverse effects across all pediatric age groups 6, 1, 4, 5

Persistent Constipation

• If constipation persists after 3-4 days of adequate PEG dosing, consider adding rectal therapy (bisacodyl or glycerin suppository) while continuing PEG 8
• Do not add fiber supplements when PEG fails—fiber is ineffective for established constipation and may worsen symptoms 8

Safety Profile

• PEG 3350 is safe across all pediatric age groups, including infants younger than 18 months (at 0.78 g/kg/day) 6
• No significant adverse effects have been reported in multiple studies with treatment durations up to 21 months 6, 4, 5, 7
• The medication is non-addictive and can be used long-term without tolerance development 7