Pediatric Dosing for Septra (Trimethoprim/Sulfamethoxazole)
For pediatric patients, Septra (trimethoprim/sulfamethoxazole) should be dosed at 8-12 mg/kg/day based on the trimethoprim component, divided into 2 doses for oral administration or 4 doses for intravenous administration. 1
Age-Specific Dosing Guidelines
Infants and Children (>2 months of age)
- Standard dosing: 8-12 mg/kg/day (based on trimethoprim component) divided every 12 hours for oral administration 1, 2
- Severity-based dosing:
Weight-Based Dosing Guide for Oral Administration
| Weight (kg) | Dose (every 12 hours) |
|---|---|
| 10-20 kg | 1 regular-strength tablet (80/400 mg) |
| 20-30 kg | 1½ regular-strength tablets |
| 30-40 kg | 2 regular-strength tablets or 1 DS tablet |
| >40 kg | Adult dosing may be used |
Indication-Specific Dosing
Skin and Soft Tissue Infections
- MRSA/MSSA infections: 8-12 mg/kg/day (trimethoprim) in 2 divided doses orally 1
- Duration: Typically 7 days, depending on clinical response 1
Urinary Tract Infections
- Standard dosing: 8 mg/kg/day trimethoprim with 40 mg/kg/day sulfamethoxazole divided every 12 hours 2
- Duration: 10-14 days for urinary tract infections 2
Other Indications
- Shigellosis: Same as UTI dosing but for 5 days 2
- Acute otitis media: 8 mg/kg/day trimethoprim with 40 mg/kg/day sulfamethoxazole divided every 12 hours for 10 days 2
Important Considerations
Age Restrictions
- Not recommended for infants less than 2 months of age 2
- Not recommended for treatment of MRSA in children under 8 years if alternatives are available 1
Renal Dosing Adjustments
- For creatinine clearance 15-30 mL/min: Use 50% of usual regimen
- For creatinine clearance <15 mL/min: Use not recommended 2
Monitoring and Safety
- Monitor for adverse effects including rash, gastrointestinal upset, and hematologic abnormalities
- Higher risk of adverse events in children with G6PD deficiency or folate deficiency
Clinical Pearls
- TMP-SMX is bactericidal but has limited published efficacy data for some indications 1
- For serious infections requiring IV administration, divide the daily dose into 4 administrations rather than 2 1
- When treating suspected MRSA infections, consider local resistance patterns before selecting TMP-SMX
- For prophylaxis of recurrent UTIs (not first-line therapy), lower doses may be used: 2 mg/kg/day trimethoprim with 10 mg/kg/day sulfamethoxazole 3
Remember that dosing should be based on the trimethoprim component when calculating pediatric doses of Septra, and duration of therapy should be tailored to the specific infection being treated.