Sulfatrim Pediatric Dosing
For most pediatric infections in children over 2 months of age, administer 8-12 mg/kg/day of trimethoprim (40-60 mg/kg/day of sulfamethoxazole) divided into two doses every 12 hours. 1, 2, 3
Age Restrictions
- Sulfatrim is contraindicated in infants under 2 months of age due to the risk of kernicterus from displacement of bilirubin from albumin binding sites 1, 3
Standard Dosing by Indication
Urinary Tract Infections and Acute Otitis Media
- 8 mg/kg/day trimethoprim (40 mg/kg/day sulfamethoxazole) divided every 12 hours for 10 days 3
- Alternative regimen: 4 mg/kg trimethoprim with 17.5 mg/kg sulphadiazine once daily has shown efficacy 4
Skin and Soft Tissue Infections (including MRSA)
Shigellosis
- 8 mg/kg/day trimethoprim (40 mg/kg/day sulfamethoxazole) divided every 12 hours for 5 days 3
- Alternative: 10 mg/kg trimethoprim with 50 mg/kg sulfamethoxazole divided every 12 hours for 5 days 5
Pneumocystis jirovecii Pneumonia (PCP)
Treatment:
- 15-20 mg/kg/day trimethoprim (75-100 mg/kg/day sulfamethoxazole) divided into 3-4 doses every 6 hours for 14-21 days 2, 3
Prophylaxis:
- 150 mg/m²/day trimethoprim with 750 mg/m²/day sulfamethoxazole divided into two doses, given three consecutive days per week 6, 3
- Alternative: 8 mg/kg/day trimethoprim divided into two doses daily 2, 6
- Maximum daily dose should not exceed 1600 mg sulfamethoxazole and 320 mg trimethoprim 3
Pertussis Prophylaxis
- 8 mg/kg/day trimethoprim (40 mg/kg/day sulfamethoxazole) for 14 days for all household and close contacts 7
Dosing Adjustments
Renal Impairment
- Creatinine clearance >30 mL/min: Use standard dosing 3
- Creatinine clearance 15-30 mL/min: Reduce to 50% of usual regimen 3
- Creatinine clearance <15 mL/min: Use not recommended 3
- For severe renal failure, increase dosing interval (hours) to 12 times the serum creatinine level (mg/dL), with a maximum interval of 48 hours 8
Monitoring Requirements
Hematologic Monitoring
- Obtain complete blood count with differential and platelet count at treatment initiation 1, 2
- Repeat monthly during prolonged therapy to detect neutropenia, thrombocytopenia, and anemia 1, 2
- Thrombocytopenia risk increases with higher serum trimethoprim levels and longer treatment duration 8
Therapeutic Drug Monitoring
- Target peak trimethoprim levels of 5-10 mcg/mL for serious infections 8
- Monitor serum concentrations in patients with severe renal failure 8
Adverse Effects and Management
Common Adverse Reactions (occur in ~15% of HIV-infected children)
- Dermatologic reactions (rash) 1, 2
- Hematologic effects (neutropenia, thrombocytopenia, anemia) 1, 2
- Gastrointestinal complaints 1
- Hepatic effects (hepatitis) 1
- Renal effects (interstitial nephritis) 1
Rash Management Algorithm
- Mild to moderate rash: Temporarily discontinue and restart when resolved 1, 2
- Urticarial rash or Stevens-Johnson syndrome: Permanently discontinue 1, 2
High-Risk Populations Requiring Caution
- G6PD deficiency: Risk of hemolytic anemia 1, 2
- Hepatic insufficiency: Requires dose adjustment consideration 1, 2
- Known sulfonamide hypersensitivity: Contraindicated 1, 2
Important Drug Interactions
- Methotrexate: May increase toxicity; use with caution 1
- Anticoagulants, hypoglycemics, thiazide diuretics, and anticonvulsants: Require monitoring 1
Pharmacokinetic Considerations
- Oral administration at 8/40 mg/kg/day divided every 12 hours achieves adult-equivalent exposure and meets pharmacodynamic targets for bacteria with MIC ≤0.5 mg/L in >90% of children 9
- For bacteria with MIC up to 1 mg/L, higher doses (12/60 mg/kg/day for ages 6-21 years or 15/75 mg/kg/day for ages 0-6 years) may be needed 9
- Half-life increases with age and serum creatinine levels 8