Pediatric Cotrimoxazole (Trimethoprim-Sulfamethoxazole) Syrup Dosing
For children over 2 months of age, administer 8-12 mg/kg/day of trimethoprim (40-60 mg/kg/day of sulfamethoxazole) divided into 2 doses given every 12 hours for standard treatment of most infections. 1, 2
Age-Based Contraindication
- Do not use cotrimoxazole in infants under 2 months of age due to the risk of kernicterus 2
Standard Treatment Dosing by Severity
Mild-to-Moderate Infections
- Use 8-10 mg/kg/day of trimethoprim divided every 12 hours for urinary tract infections, skin and soft tissue infections, or non-severe pneumonia 1, 2
Serious Infections
- Use 10-12 mg/kg/day of trimethoprim divided every 12 hours for severe MRSA infections 1
- For life-threatening infections, doses up to 15-20 mg/kg/day divided every 6-8 hours may be used 1
Severe MRSA Osteomyelitis
- Administer 4 mg/kg/dose of trimethoprim every 8-12 hours, typically combined with rifampin for >6 weeks 1
Weight-Based Practical Dosing Table
For achieving 8 mg/kg trimethoprim per dose every 12 hours 1:
| Weight | Dose per administration |
|---|---|
| 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 |
Formulation Considerations
- Use liquid formulation for children weighing <16 kg to ensure accurate dosing, as recommended for younger children 1, 3
Renal Impairment Adjustments
- CrCl 10-50 mL/min: Administer 3-5 mg/kg every 12 hours (instead of every 6-8 hours) 1
- CrCl <10 mL/min: Administer 3-5 mg/kg every 24 hours 1
- CrCl 15-30 mL/min: Reduce dose by 50% 1
- CrCl <15 mL/min: Reduce dose by 50% or use an alternative agent 1
Prophylaxis Dosing (Special Circumstances)
For Pneumocystis jirovecii pneumonia (PCP) prophylaxis in immunocompromised children:
- 150 mg/m²/day trimethoprim with 750 mg/m²/day sulfamethoxazole, divided into 2 doses, given 3 consecutive days per week 1, 3
- Maximum: 320 mg trimethoprim/1600 mg sulfamethoxazole daily 1
For pertussis prophylaxis:
- 8 mg/kg/day trimethoprim (40 mg/kg/day sulfamethoxazole) for 14 days for all household and close contacts 2
Monitoring Requirements
- Obtain complete blood count with differential and platelet count at treatment initiation 1, 2
- Repeat monthly during prolonged therapy to assess for hematologic toxicity including neutropenia, thrombocytopenia, and anemia 1, 2
Critical Safety Precautions
- Screen for G6PD deficiency before initiating therapy due to hemolytic anemia risk 1, 2
- Use with caution in patients with renal insufficiency, hepatic insufficiency, and G6PD deficiency 1, 2
- Ensure adequate hydration (at least 1.5 liters daily) to prevent crystalluria 1
- Avoid in patients with severe hepatic impairment 1
Important Drug Interactions
- May increase methotrexate toxicity 1, 2
- Enhances anticoagulant effect of warfarin 1, 2
- Increases hypoglycemia risk with oral hypoglycemics 1, 2
- Use caution with thiazide diuretics and anticonvulsants 2
Common Adverse Effects
Adverse reactions occur in approximately 15% of HIV-infected children 2:
- Dermatologic reactions (rash) 2
- Hematologic effects (neutropenia, thrombocytopenia, anemia) 2
- Gastrointestinal complaints 2
- Hepatic effects (hepatitis) 2
- Renal effects (interstitial nephritis) 2