What is the recommended dosage of Septrin (co-trimoxazole) for a 50kg patient with Stenotrophomonas infection?

Dosage of Co-trimoxazole (Septrin) for Stenotrophomonas maltophilia Infection in a 50kg Patient

For a 50kg patient with Stenotrophomonas maltophilia infection, the recommended dosage of co-trimoxazole (Septrin) is 15-20 mg/kg/day of trimethoprim component (750-1000 mg/day) divided into two doses every 12 hours. 1, 2

Dosing Calculation

• For a 50kg patient:

  • Standard dosing: 15-20 mg/kg/day of trimethoprim component 1
  • Calculation: 50kg × 15-20 mg/kg = 750-1000 mg trimethoprim per day 1
  • Divided into two equal doses (every 12 hours) 1

• Practical administration:

  • Each double-strength (DS) tablet contains 160 mg trimethoprim/800 mg sulfamethoxazole 1
  • Recommended dosage: 2-3 DS tablets daily, divided into two doses (1-1.5 DS tablets every 12 hours) 1, 3

Treatment Considerations

Duration of Therapy

• For Stenotrophomonas maltophilia pneumonia: 14 days of therapy is typically recommended 4
• For other infections: 10-14 days, depending on clinical response and infection site 1

Monitoring

• Monitor renal function regularly, as dose adjustment is required for patients with impaired renal function 1
  • For creatinine clearance 15-30 mL/min: reduce dose by 50% 1
  • For creatinine clearance <15 mL/min: not recommended 1
• Monitor for adverse effects including:
  • Hyperkalemia 4
  • Acute kidney injury 4
  • Skin reactions 3

Efficacy Considerations

• Co-trimoxazole remains the treatment of choice for Stenotrophomonas maltophilia infections 3, 5
• Recent research shows that both low-dose (8-12 mg/kg/day) and high-dose (>12 mg/kg/day) regimens have similar clinical success rates for pneumonia 4
• The pharmacodynamic target for effective treatment is an fAUC/MIC of approximately 67.4 for trimethoprim component 2

Alternative Options

• If co-trimoxazole cannot be used due to resistance or allergies, consider:
  • Minocycline (comparable efficacy to co-trimoxazole in some studies) 3
  • Ciprofloxacin (90% success rate in case reports) 5
  • Ceftazidime or ceftriaxone-based regimens (75% success rate in case reports) 5

Special Considerations

• Synergistic combinations may be beneficial for multidrug-resistant strains:
  • Co-trimoxazole with colistin 6
  • Co-trimoxazole with rifampin 6
• For severe infections, consider using the higher end of the dosing range (20 mg/kg/day of trimethoprim component) 2, 4