Pediatric Mesalazine Dosing for Ulcerative Colitis
For children with mild-to-moderately active ulcerative colitis, use weight-based oral mesalazine at 50–100 mg/kg/day (maximum 4.8 g/day) given once daily, with lower doses of 30–50 mg/kg/day for maintenance of remission.
Active Disease Treatment (Induction)
Weight-Based Dosing Strategy
Administer 50–100 mg/kg/day once daily for children with mild-to-moderately active ulcerative colitis, with a maximum daily dose of 4.8 g regardless of weight 1, 2.
A randomized pediatric trial demonstrated that low-dose (27–71 mg/kg/day) and high-dose (53–118 mg/kg/day) mesalamine achieved identical treatment success rates of 55–56%, with no additional benefit from higher dosing 2.
Multimatrix mesalamine at 30,60, or 100 mg/kg/day once daily (up to 4,800 mg/day) produced dose-proportional systemic exposure and was well tolerated across all pediatric age groups (5–17 years) 1.
Practical Dosing by Weight
For children 18–30 kg: Start with 1.2–2.4 g/day once daily 1, 2.
For children 31–50 kg: Start with 2.4–3.6 g/day once daily 1, 2.
For adolescents >50 kg: Start with 3.6–4.8 g/day once daily, mirroring adult high-dose regimens 1, 2.
Once-daily dosing is as effective as divided dosing and should be preferred to improve adherence 3, 4.
Maintenance Therapy
Standard Maintenance Dosing
Use 30–50 mg/kg/day (approximately 1–2 g/day for most children) once daily to maintain remission after induction 5, 6.
For children with frequent relapses or extensive disease, escalate maintenance to 60–80 mg/kg/day (up to 3 g/day) 5.
Combined Oral and Rectal Therapy
For left-sided or extensive disease, add rectal mesalamine (enemas ≥1 g/day or suppositories 1 g/day for proctitis) to oral therapy, as combination therapy is superior to oral therapy alone 3, 5.
The combination of oral mesalamine ≥2.4 g/day plus rectal mesalamine ≥1 g/day is more effective than either modality alone for both induction and maintenance 3.
Pharmacokinetic Considerations
Pediatric pharmacokinetics mirror adult profiles: A single 20 mg/kg dose produced a mean Cmax of 1332 ng/mL at 3.7 hours, with a terminal half-life of 3.5 hours and systemic bioavailability of 22–29% 1, 6.
Steady-state exposures in children are similar to adults at comparable mg/kg doses, supporting weight-based extrapolation from adult data 1.
Treatment Duration and Response Monitoring
If rectal bleeding persists beyond 10–14 days or sustained symptom relief is not achieved by 40 days, escalate to systemic corticosteroids rather than continuing suboptimal mesalamine 3, 8.
Do not continue mesalamine monotherapy in children with progressively worsening symptoms, weight loss, or extraintestinal manifestations—these patients require corticosteroids, immunomodulators, or biologics 3, 8.
Common Pitfalls and Caveats
Avoid underdosing: Doses <50 mg/kg/day for active disease are subtherapeutic and delay effective treatment 8, 9, 2.
Mesalamine intolerance occurs in up to 15% of children, presenting as paradoxical worsening diarrhea, headache, nausea, or rash; acute intolerance mimics a flare and recurs on rechallenge 9.
Monitor renal function periodically, as rare interstitial nephritis and nephrotic syndrome have been reported with mesalamine 9.
Mesalamine is ineffective for Crohn's disease maintenance in children; if Crohn's disease is suspected or confirmed, switch to azathioprine (1.5–2.5 mg/kg/day) or biologics 8, 9.
When to Escalate Beyond Mesalamine
If children require ≥2 courses of corticosteroids per year despite optimized mesalamine, escalate to thiopurines, anti-TNF therapy, vedolizumab, or tofacitinib 5.
High-risk features (young age at diagnosis, extensive disease, deep ulcers, or failure of mesalamine within 6–8 weeks) warrant early introduction of immunomodulators or biologics rather than prolonged mesalamine trials 8, 5.