What is the recommended dose of Sulfatrim (sulfamethoxazole and trimethoprim) for pediatric patients?

Recommended Dosage of Sulfatrim (Sulfamethoxazole and Trimethoprim) for Pediatric Patients

For pediatric patients 2 months of age or older, the recommended dose of Sulfatrim (sulfamethoxazole and trimethoprim) is 40 mg/kg sulfamethoxazole and 8 mg/kg trimethoprim per 24 hours, given in two divided doses every 12 hours. 1, 2

Age Restrictions

• Sulfatrim is contraindicated in pediatric patients less than 2 months of age 1, 2

Dosing Guidelines by Weight

For children 2 months of age or older:

Weight (kg)	Weight (lb)	Dose (every 12 hours)
10	22	1/2 tablet
20	44	1 tablet
30	66	1 1/2 tablets
40	88	2 tablets or 1 DS tablet

1, 2

Dosing for Specific Conditions

Urinary Tract Infections and Acute Otitis Media

• 40 mg/kg sulfamethoxazole and 8 mg/kg trimethoprim per 24 hours
• Given in two divided doses every 12 hours
• Treatment duration: 10 days 1

Shigellosis

• Same dosage as UTI: 40 mg/kg sulfamethoxazole and 8 mg/kg trimethoprim per 24 hours
• Given in two divided doses every 12 hours
• Treatment duration: 5 days 1, 3

Pneumocystis jiroveci Pneumonia Treatment

• 75 to 100 mg/kg sulfamethoxazole and 15 to 20 mg/kg trimethoprim per 24 hours
• Given in equally divided doses every 6 hours
• Treatment duration: 14 to 21 days 1, 2

Pneumocystis Prophylaxis

• 750 mg/m² sulfamethoxazole with 150 mg/m² trimethoprim per day
• Given orally in equally divided doses twice a day, on 3 consecutive days per week
• Maximum daily dose: 1600 mg sulfamethoxazole and 320 mg trimethoprim 1, 2

Dosage Adjustments

Renal Impairment

• Creatinine clearance >30 mL/min: Standard dosage regimen
• Creatinine clearance 15-30 mL/min: Half the usual regimen
• Creatinine clearance <15 mL/min: Not recommended 1, 2

Pharmacokinetic Considerations

• Weight-based dosing is essential as TMP and SMX clearance varies with age 4
• Both TMP and SMX clearance increase with age, requiring higher mg/kg doses in younger children to achieve therapeutic levels 4
• Serum concentrations of TMP-SMX should be monitored in patients with severe renal impairment 5

Clinical Pearls

• Oral absorption of TMP-SMX in children is reliable and achieves therapeutic levels 4
• For optimal efficacy against bacteria with MIC of 0.5 mg/L, the standard dose of 8/40 mg/kg/day divided every 12 hours is sufficient 4
• For bacteria with higher MICs (up to 1 mg/L), higher doses may be required: 12/60 mg/kg/day for children 6 to <21 years and 15/75 mg/kg/day for children 0 to <6 years 4
• Regular monitoring of complete blood counts is recommended when initiating TMP-SMX therapy to assess for hematologic toxicity 6

Common Pitfalls to Avoid

• Using TMP-SMX in infants younger than 2 months (contraindicated) 1, 2
• Failure to adjust dosing in renal impairment, which can lead to drug accumulation 1, 5
• Not accounting for age-related differences in clearance when dosing 4
• Overlooking the need for higher dosing when treating resistant organisms 4