What are the best medications for constipation in pediatric patients?

Best Medications for Pediatric Constipation

Polyethylene glycol 3350 (PEG 3350) is the first-line pharmacological treatment for constipation in pediatric patients, demonstrating superior efficacy and fewer side effects compared to other laxatives. 1

First-Line Treatment: PEG 3350

PEG 3350 should be initiated as the primary laxative agent for children with functional constipation, with a starting dose of 0.4 g/kg/day (approximately 0.78 g/kg/day for maintenance in infants). 2, 3

Dosing by Age Group:

• Infants (<18 months): Start at 0.78 g/kg/day, which has been proven safe and effective with 97.6% success rate 3
• Children ≥18 months: Start at 0.4 g/kg/day, which provides optimal balance between efficacy and tolerability 2
• Older children (≥6 years): Can start with 2 sachets/day (approximately 17g daily for adults, scaled to pediatric dosing) 1

Evidence Supporting PEG 3350:

PEG 3350 achieved a 56% success rate (defined as ≥3 bowel movements/week and ≤1 encopresis episode every two weeks) compared to only 29% with lactulose in a large randomized controlled trial. 1 In dose-ranging studies, 73-77% of children receiving PEG 3350 achieved successful treatment (≥3 bowel movements in the second week) versus only 42% with placebo. 2

PEG 3350 produces significantly less abdominal pain, straining, and pain at defecation compared to lactulose, though patients may report worse taste. 1

Second-Line Treatment: Lactulose

Lactulose remains an effective alternative when PEG 3350 is unavailable or not tolerated, though it requires higher doses and produces more gastrointestinal side effects. 1, 4

Lactulose Dosing (FDA-Approved):

• Infants: 2.5-10 mL daily in divided doses 5
• Older children and adolescents: 40-90 mL total daily dose 5
• Goal: Produce 2-3 soft stools daily 5

Critical caveat: If initial lactulose dose causes diarrhea, reduce immediately; if diarrhea persists, discontinue lactulose. 5 Lactulose contains galactose (<1.6 g/15 mL) and lactose (<1.2 g/15 mL), requiring caution in diabetic patients. 5 Infants receiving lactulose may develop hyponatremia and dehydration, necessitating close monitoring. 5

Adjunctive Therapies for Specific Scenarios

Stimulant Laxatives (Senna, Bisacodyl):

Stimulant laxatives should be reserved as adjunctive therapy or for rescue treatment, not as monotherapy. 4 These agents work best when combined with osmotic laxatives for refractory cases.

Fruit Juices (Prune, Pear, Apple):

Juices containing sorbitol can be used to increase stool frequency and water content in infants with mild constipation, taking advantage of carbohydrate malabsorption. 6 However, this approach should not replace pharmacological therapy in established functional constipation.

Probiotics, Fiber, Suppositories:

These agents serve as excellent adjunct therapies in specific clinical scenarios but lack the robust evidence base of PEG 3350 for primary treatment. 4

Treatment Algorithm

1. Rule out fecal impaction through digital rectal examination before initiating maintenance therapy 7
2. Start PEG 3350 at 0.4 g/kg/day (or 0.78 g/kg/day in infants <18 months) 2, 3
3. Titrate dose based on response, aiming for soft, non-forced bowel movements every 1-2 days 7
4. If inadequate response after 1-2 weeks, increase PEG dose or add stimulant laxative 4
5. If PEG not tolerated or unavailable, switch to lactulose at age-appropriate dosing 5, 1
6. Continue maintenance therapy for several months to prevent recurrence, as functional constipation often requires prolonged treatment 3

Common Pitfalls to Avoid

Do not rely on stool softeners (docusate) alone, as they have no proven benefit for pediatric constipation. 8

Avoid fiber supplementation without adequate fluid intake and physical activity, as fiber can worsen symptoms in children with reduced gastrointestinal motility. 8

Do not use stimulant laxatives as monotherapy in young children, as they work best in combination with osmotic agents. 4

Never assume adequate dosing has been achieved based on loose stools from other laxatives during initial therapy, as this may falsely suggest therapeutic success. 5

Safety Profile

PEG 3350 demonstrates excellent safety across all pediatric age groups, with the most common adverse effect being transient diarrhea that resolves with dose adjustment. 3, 2 Only 9 of 46 patients (20%) experienced diarrhea, and no serious adverse events were reported in studies spanning up to 21 months of treatment. 3