What are the recommended pediatric and adult doses of polyethylene glycol (PEG 3350) for treating constipation?

Polyethylene Glycol Dosing

For adults with chronic constipation, use polyethylene glycol 3350 at 17 g once daily, and for children, start with 0.4 g/kg/day (approximately 0.8 g/kg/day for maintenance therapy). 1

Adult Dosing

The FDA-approved and guideline-recommended dose for adults is 17 g once daily, mixed in 4-8 ounces of any beverage 1, 2. This dose:

• Is approved for occasional constipation but has demonstrated efficacy for chronic idiopathic constipation for up to 6 months 1
• Can be titrated based on symptom response and side effects with no clear maximum dose 1
• Should be fully dissolved before drinking; do not use if clumps remain 2

Key adult considerations:

• The 17 g daily dose significantly increases complete spontaneous bowel movements (mean difference 2.90 per week) and overall bowel movement frequency (mean difference 2.30 per week) compared to placebo 1
• Response is durable over 6 months of continuous use 1
• For acute relief within 24 hours, higher doses (68 g as a single dose) have been studied but are not standard practice 3

Pediatric Dosing

For Functional Constipation (Maintenance):

Start with 0.4 g/kg/day for children aged 2 years and older 4. This dose can be adjusted every 3 days to achieve 2 soft stools per day, with an effective range of 0.27-1.42 g/kg/day (mean effective dose 0.8 g/kg/day) 5.

Specific pediatric evidence:

• The 0.4 g/kg/day dose significantly improved bowel movement frequency and stool consistency with fewer side effects than higher doses 4
• The 0.8 g/kg/day dose, while effective, caused more abdominal pain and fecal incontinence 4
• Mean effective maintenance dose across studies is approximately 0.74-0.84 g/kg/day 5

For Children Under 2 Years:

Consult a physician - FDA labeling recommends asking a doctor for children 16 years and under, though real-world data shows usage in children under 2 years with a median dose of one sachet (6.9 g) daily 2, 6. Safety data in this age group shows no concerning signals, but electrolyte monitoring may be prudent 6.

For Home Cleanouts (Disimpaction):

Pediatric gastroenterology practices use significantly higher doses:

• 1-day cleanout: median 5.3 g/kg/day 7
• 2-day cleanout: median 4.6 g/kg/day 7

These doses are substantially higher than standard maintenance dosing and should be used under specialist guidance.

Practical Administration

Mixing instructions:

• Dissolve powder completely in 4-8 ounces of any temperature beverage (cold, hot, or room temperature) 2
• Do not combine with starch-based thickeners used for dysphagia 2
• Ensure adequate hydration throughout treatment 1

Duration:

• FDA labeling states "do not use more than 7 days" for over-the-counter use 2
• However, clinical evidence supports safe use for up to 6 months for chronic constipation 1

Common Pitfalls to Avoid

1. Underdosing in children: The 0.2 g/kg/day dose, while effective, is less optimal than 0.4 g/kg/day for symptom control 4

2. Inadequate dissolution: Drinking incompletely dissolved powder reduces efficacy and palatability 2

3. Premature discontinuation: Most gastrointestinal side effects (bloating, cramping) occur in the first week and decrease markedly thereafter 8

4. Ignoring dose titration: The dose should be adjusted based on stool frequency and consistency, not arbitrarily maintained 1

Expected Side Effects

Common and generally mild side effects include 1:

• Bloating and abdominal discomfort
• Flatulence
• Diarrhea (158 more per 1,000 treated patients)
• Cramping

These effects are consistent with osmotic laxative therapy and most are mild to moderate in severity. Serious adverse events are rare with no significant difference from placebo 1.