What is the recommended dosage and treatment regimen for Cotrimoxazole (trimethoprim/sulfamethoxazole)?

Recommended Dosage and Treatment Regimens for Cotrimoxazole (Trimethoprim/Sulfamethoxazole)

The recommended dosage of cotrimoxazole (trimethoprim/sulfamethoxazole) varies by indication, with urinary tract infections typically treated with one double-strength tablet (160mg/800mg) twice daily for 3 days in uncomplicated cases, while more severe infections require higher doses and longer durations. 1

Adult Dosing Regimens by Indication

Urinary Tract Infections

• Uncomplicated UTI:
  • 1 double-strength tablet (160mg/800mg) twice daily for 3 days 2
  • Alternative: 2 double-strength tablets twice daily for 1 day 3, 4
• Complicated UTI:
  • 1 double-strength tablet twice daily for 10-14 days 1
• Pyelonephritis:
  • 1 double-strength tablet twice daily for 14 days 2
  • Consider initial IV dose of ceftriaxone 1g if fluoroquinolone resistance >10% 2

Skin and Soft Tissue Infections

• MRSA infections:
  • 1-2 double-strength tablets twice daily 2
  • Duration: Based on clinical response, typically 7-14 days

Respiratory Infections

• Acute exacerbations of chronic bronchitis:
  • 1 double-strength tablet (or 4 teaspoonfuls of suspension) twice daily for 14 days 1

Pneumocystis jirovecii Pneumonia

• Treatment:
  • 15-20 mg/kg/day of trimethoprim component (75-100 mg/kg/day of sulfamethoxazole) divided into doses every 6 hours for 14-21 days 1
• Prophylaxis:
  • 1 double-strength tablet daily 1

Traveler's Diarrhea

• 1 double-strength tablet twice daily for 5 days 1

Pertussis (Whooping Cough)

• Trimethoprim 8 mg/kg/day, sulfamethoxazole 40 mg/kg/day in 2 divided doses for 14 days 2

Pediatric Dosing

• Children >2 months:

  • UTI/Otitis media: 8 mg/kg/day trimethoprim and 40 mg/kg/day sulfamethoxazole divided every 12 hours for 10 days 1
  • Shigellosis: Same dose as above for 5 days 1

• Weight-based dosing guide:

  • 10 kg: 1 teaspoonful (5 mL) twice daily
  • 20 kg: 2 teaspoonfuls (10 mL) twice daily
  • 30 kg: 3 teaspoonfuls (15 mL) twice daily
  • 40 kg: 4 teaspoonfuls (20 mL) twice daily 1

• Contraindicated in infants <2 months due to risk of kernicterus 2, 1

Dosage Adjustments

Renal Impairment

• CrCl >30 mL/min: Standard regimen
• CrCl 15-30 mL/min: Half the usual regimen
• CrCl <15 mL/min: Not recommended 1

Elderly Patients

• May require dose adjustment due to higher peak concentrations and reduced clearance of trimethoprim 5

Treatment Duration Considerations

• Uncomplicated UTI: 3 days is as effective as 7 days with fewer side effects 6
• Complicated UTI: 10-14 days 1
• Pyelonephritis: 14 days 2
• Pertussis: 14 days 2

Monitoring and Safety

• Monitor complete blood counts with differential and platelet count at initiation and monthly for prolonged therapy 5
• Common side effects include gastrointestinal disturbances, hypersensitivity reactions, and rarely Stevens-Johnson syndrome 2, 5
• Higher incidence of adverse effects with longer treatment durations 6

Important Considerations

• Always consider local resistance patterns when prescribing empirically 2, 5
• Contraindicated in pregnancy (third trimester) due to risk of kernicterus 2
• For patients unable to tolerate TMP-SMX due to adverse reactions, temporary discontinuation with rechallenge after 2 weeks may be attempted 5
• Single-day or 3-day regimens for uncomplicated UTIs show comparable efficacy to longer courses with fewer side effects 3, 4, 6