Cotrimoxazole Dosing for Pediatric and Adult Patients
Pediatric Dosing (Children >2 months)
For treatment of most infections in children, administer 8-12 mg/kg/day of trimethoprim (40-60 mg/kg/day of sulfamethoxazole) divided into 2 doses every 12 hours. 1, 2, 3
Standard Treatment Dosing by Indication
Urinary tract infections and acute otitis media: 8 mg/kg trimethoprim (40 mg/kg sulfamethoxazole) per 24 hours, divided every 12 hours for 10 days 3
Skin and soft tissue infections: 8-12 mg/kg/day of trimethoprim for 7-10 days 1
Non-severe pneumonia: 8 mg/kg trimethoprim per dose, twice daily 4
Shigellosis: Same as UTI dosing (8 mg/kg trimethoprim daily) for 5 days 3
Severe infections (e.g., MRSA osteomyelitis): 10-12 mg/kg/day of trimethoprim, or up to 15-20 mg/kg/day divided every 6-8 hours for life-threatening infections 2
Pneumocystis Jirovecii Pneumonia (PCP)
Treatment: 75-100 mg/kg/day sulfamethoxazole with 15-20 mg/kg/day trimethoprim, divided every 6 hours for 14-21 days 3
Prophylaxis: 150 mg/m²/day trimethoprim with 750 mg/m²/day sulfamethoxazole, divided twice daily, given 3 consecutive days per week (maximum 320 mg trimethoprim/1600 mg sulfamethoxazole daily) 4, 5, 3
HIV-exposed infants: Begin prophylaxis at 4-6 weeks of age and continue throughout the first year until HIV infection is ruled out 5
Weight-Based Dosing Table (Standard Treatment)
For achieving 8 mg/kg trimethoprim per dose every 12 hours: 3
- 10 kg (22 lbs): 1 single-strength tablet (80 mg TMP/400 mg SMX)
- 20 kg (44 lbs): 1 single-strength tablet
- 30 kg (66 lbs): 1½ single-strength tablets
- 40 kg (88 lbs): 2 single-strength tablets OR 1 double-strength tablet
Important Pediatric Considerations
Contraindicated in infants <2 months due to risk of kernicterus 1, 3
Use liquid formulation for accurate dosing in children weighing <16 kg 2
The standard 8/40 mg/kg/day dosing achieves therapeutic targets for bacteria with MIC ≤0.5 mg/L in >90% of children 6
Adult Dosing
For most infections in adults, administer 1 double-strength tablet (160 mg trimethoprim/800 mg sulfamethoxazole) every 12 hours. 3
Standard Treatment Dosing by Indication
Urinary tract infections: 1 double-strength tablet every 12 hours for 10-14 days 3
Acute exacerbations of chronic bronchitis: 1 double-strength tablet every 12 hours for 14 days 3
Shigellosis: 1 double-strength tablet every 12 hours for 5 days 3
Traveler's diarrhea: 1 double-strength tablet every 12 hours for 5 days 3
Pneumocystis Jirovecii Pneumonia (PCP)
Treatment: 15-20 mg/kg/day trimethoprim (75-100 mg/kg/day sulfamethoxazole) divided every 6 hours for 14-21 days 3
Prophylaxis: 1 double-strength tablet daily 3
Renal Impairment Adjustments
Dose reduction is mandatory in renal impairment to prevent toxicity. 2
CrCl >30 mL/min: Standard dosing 3
CrCl 10-50 mL/min (treatment dosing): 3-5 mg/kg every 12 hours instead of every 6-8 hours 2
CrCl <15 mL/min: Reduce dose by 50% or use alternative agent 2, 3
CrCl <10 mL/min (treatment dosing): 3-5 mg/kg every 24 hours 2
Ensure adequate hydration (at least 1.5 liters daily) to prevent crystalluria 2
Monitoring Requirements
Obtain complete blood count with differential and platelet count at treatment initiation, and repeat monthly during prolonged therapy. 1, 5, 2
Monitor for hematologic toxicity including neutropenia, thrombocytopenia, and anemia 1, 5
Approximately 15% of HIV-infected children experience adverse reactions 1
Key Safety Considerations
Contraindicated in severe hepatic impairment 2
Use with extreme caution in G6PD deficiency due to risk of hemolytic anemia 1, 2
Drug interactions: May increase methotrexate toxicity, enhance warfarin anticoagulant effect, and increase hypoglycemia risk with oral hypoglycemics 1, 2
For mild rash: Temporarily discontinue and restart when resolved 1
For urticarial rash or Stevens-Johnson syndrome: Permanently discontinue 1