What is the recommended dose of Septran DS (Sulfamethoxazole and Trimethoprim) for prophylaxis in a 16kg child?

Recommended Dose of Septran DS for Prophylaxis in a 16kg Child

The recommended dose of Septran DS (Trimethoprim-Sulfamethoxazole) for prophylaxis in a 16kg child is 8 mg/kg of trimethoprim component daily, which equals approximately 128 mg of trimethoprim per day, typically divided into two doses.

Dosage Calculation

• For children, the FDA-approved prophylactic dosage of trimethoprim-sulfamethoxazole is 750 mg/m² per day of sulfamethoxazole with 150 mg/m² per day of trimethoprim, given in equally divided doses twice daily 1
• Alternatively, for weight-based dosing, the recommended prophylactic dose is 8 mg/kg/day of the trimethoprim component divided into two doses 2
• For a 16kg child, this would equal 128 mg of trimethoprim per day, or 64 mg twice daily 1

Administration Schedule

• The prophylactic regimen can be administered in different schedules depending on the indication:
  • Daily administration (continuous prophylaxis) 1
  • Three consecutive days per week 2
  • Two non-consecutive days per week has also been shown to be effective in immunocompromised children 3

Specific Indications for Prophylaxis

• Pneumocystis jiroveci pneumonia (PCP) prophylaxis in immunocompromised children 2
• Prevention of recurrent urinary tract infections 4
• Post-exposure prophylaxis for certain infections (though this is an alternative, not first-line agent) 2

Important Considerations

• Septran DS (Double Strength) tablets contain 160 mg trimethoprim and 800 mg sulfamethoxazole per tablet 1
• For a 16kg child, liquid formulation may be more appropriate for accurate dosing 2
• Trimethoprim-sulfamethoxazole is contraindicated in children less than 2 months of age 1
• Regular monitoring is recommended:
  • Complete blood counts with differential and platelet count should be performed at initiation of TMP-SMX prophylaxis and monthly thereafter to assess for hematologic toxicity 2

Dose Adjustments

• Dose adjustment is necessary in patients with renal impairment:
  • For creatinine clearance 15-30 mL/min: use half the usual regimen
  • For creatinine clearance below 15 mL/min: use is not recommended 1

Potential Adverse Effects

• Common side effects include rash, gastrointestinal disturbances, and hematologic abnormalities 2
• If life-threatening toxicity occurs (anaphylaxis, Stevens-Johnson syndrome), the drug should be permanently discontinued 2
• For other potentially drug-related reactions (rash, neutropenia), the drug can be temporarily discontinued and tried again within 2 weeks 2

By following these dosing guidelines, trimethoprim-sulfamethoxazole can be safely and effectively used for prophylaxis in a 16kg child, with appropriate monitoring for potential adverse effects.