What is the dosing for Trimethoprim (TMP)-Sulfamethoxazole (SMZ) in pediatric patients?

From the Guidelines

Trimethoprim-sulfamethoxazole (TMP-SMX) dosing for pediatric patients is typically 8-12 mg/kg/day of trimethoprim (based on the trimethoprim component) in either 4 divided doses intravenously or 2 divided doses orally. The most recent and highest quality study 1 provides the dosing guidelines for TMP-SMX in pediatric patients. According to this study, the recommended dosage is 8-12 mg/kg/day of trimethoprim, which is consistent with other studies 1.

Key Considerations

• The dosage is based on the trimethoprim component, with 8-12 mg/kg/day being the standard dose for most infections.
• The medication should be divided into 2-4 doses, depending on the severity of the infection and the patient's response to treatment.
• TMP-SMX should be used cautiously in infants under 2 months due to the risk of kernicterus.
• Adequate hydration should be maintained during treatment, and the medication should be taken with food to minimize gastrointestinal side effects.

Important Details

• For urinary tract infections, a common dosage is 6-12 mg/kg/day of trimethoprim divided twice daily for 3-14 days, depending on infection severity.
• For Pneumocystis jirovecii pneumonia treatment, higher doses of 15-20 mg/kg/day of trimethoprim divided into 3-4 doses are used for 14-21 days.
• For PJP prophylaxis, 150 mg/m² of trimethoprim (750 mg/m² of sulfamethoxazole) is given twice daily for three consecutive days per week.

Mechanism of Action

• TMP-SMX works by inhibiting two sequential steps in bacterial folate synthesis, making it effective against many common pediatric pathogens.
• However, resistance patterns should be considered when prescribing, as the efficacy of TMP-SMX can be limited by the development of resistant strains 1.

From the FDA Drug Label

Children: The recommended dose for children with urinary tract infections or acute otitis media is 40 mg/kg sulfamethoxazole and 8 mg/kg trimethoprim per 24 hours, given in two divided doses every 12 hours for 10 days. The following table is a guideline for the attainment of this dosage: Children 2 months of age or older: Weight Dose-every 12 hours lb kg Tablets 22-44 10-20 1 66-88 30-40 2 (400 mg/80 mg) or 1 (DS) tablet

The dosing for Trimethoprim (TMP)-Sulfamethoxazole (SMZ) in pediatric patients is 40 mg/kg sulfamethoxazole and 8 mg/kg trimethoprim per 24 hours, given in two divided doses every 12 hours for 10 days, for children with urinary tract infections or acute otitis media, and for children 2 months of age or older.

• The dose is divided into two doses every 12 hours.
• The dosage can also be determined using the provided weight-based table. 2

From the Research

Dosing for Trimethoprim (TMP)-Sulfamethoxazole (SMZ) in Pediatric Patients

• The optimal dosing for TMP-SMZ in pediatric patients is based on the matching adult TMP exposure and attainment of the surrogate pharmacodynamic (PD) target for efficacy, a free TMP concentration above the MIC over 50% of the dosing interval 3.
• For pediatric patients, the exposure achieved after oral administration of TMP-SMX at 8/40 mg/kg of body weight/day divided into administration every 12 h matches the exposure achieved in adults after administration of TMP-SMX at 320/1,600 mg/day divided into administration every 12 h and achieves the PD target for bacteria with an MIC of 0.5 mg/liter in >90% of infants and children 3.
• Higher doses of 12/60 and 15/75 mg/kg/day divided into administration every 12 h are optimal for bacteria with an MIC of up to 1 mg/liter in subjects 6 to <21 years and 0 to <6 years of age, respectively 3.
• Intermittent low-dose TMP-SMZ has been used in children with vesicoureteral reflux, with a dose of 1 mg/kg body weight of trimethoprim together with 5 mg/kg of sulfamethoxazole at bedtime every other day 4.
• In pediatric urinary tract infection, trimethoprim (TMP) as a single therapeutic agent has been studied, with a cure rate of 100% compared to TMP/Sulfa 100% 5.
• The pharmacokinetics of intravenous TMP-SMZ in children and adults with normal and impaired renal function have been studied, with a recommended loading dose of 250 mg of TMP and 1,250 mg of SMZ/m2, followed by maintenance doses of 150 mg of TMP and 750 mg of SMZ/m2 every 8 hr for children aged 10 years or younger and every 12 hr for adults with normal renal function 6.
• For acute otitis media, a single intramuscular dose of ceftriaxone has been compared to 10 days of oral TMP-SMZ, with 8 mg of TMP and 40 mg of SMZ/kg/day in two divided doses 7.