What is the dose of Septran DS (sulfamethoxazole and trimethoprim) for Pneumocystis jirovecii pneumonia prophylaxis in a 10kg female?

Dosage of Septran DS (TMP-SMX) for Pneumocystis Jirovecii Pneumonia Prophylaxis in a 10kg Child

For a 10kg child, the recommended dose of Septran DS (trimethoprim-sulfamethoxazole) for Pneumocystis jirovecii pneumonia prophylaxis is 150 mg/m² per day of trimethoprim component (approximately one-half tablet of Septran DS daily or one-half tablet three times weekly). 1, 2

Dosing Calculation and Options

• For children, the FDA-approved dosage for PJP prophylaxis is 750 mg/m²/day sulfamethoxazole with 150 mg/m²/day trimethoprim given orally in equally divided doses twice a day, on 3 consecutive days per week 1
• For a 10kg child (approximately 0.5 m² body surface area), this translates to approximately:
  • One-half tablet of Septran DS (400mg/80mg) daily, OR
  • One-half tablet of Septran DS three times weekly (typically Monday-Wednesday-Friday) 2, 1
• The total daily dose should not exceed 1600 mg sulfamethoxazole and 320 mg trimethoprim 1

Administration Guidelines

• The medication can be given as a single daily dose or divided into two doses 1
• For children who cannot swallow tablets, the tablet can be crushed and mixed with food or liquid 2
• Ensure adequate hydration during treatment to prevent crystalluria and stone formation 3

Monitoring and Precautions

• Regular monitoring for adverse effects is essential, including:
  • Complete blood counts with differential and platelet counts 2
  • Renal function tests, especially in patients with underlying kidney disease 3
• Common adverse effects include rash, pruritus, cytopenias, and transaminase elevations 2
• For patients with creatinine clearance 15-30 mL/min, the dose should be reduced by half 3
• For patients with creatinine clearance <15 mL/min, TMP-SMX is not recommended and alternative agents should be considered 3

Alternative Regimens

• If TMP-SMX is not tolerated, alternative prophylactic regimens include:
  • Dapsone (2 mg/kg/day, maximum 100 mg daily) 2
  • Atovaquone (30 mg/kg daily) 2
• However, TMP-SMX remains the first-line agent due to superior efficacy compared to alternatives 2

Duration of Prophylaxis

• Prophylaxis should be continued as long as the immunosuppressive condition persists 3, 2
• For HIV-infected children, prophylaxis should be continued until immune reconstitution occurs (typically CD4+ T-cell counts >200 cells/μL for at least 3 consecutive months) 2

TMP-SMX prophylaxis has been shown to be highly effective in preventing PJP in immunocompromised children, with studies showing excellent efficacy and relatively low rates of adverse effects when appropriate dosing is used 4, 5.