What is the recommended Bactrim (trimethoprim/sulfamethoxazole) dosing for prophylaxis against urinary tract infections in pediatric patients with vesicoureteric reflux?

From the Guidelines

For prophylaxis against urinary tract infections in pediatric patients with vesicoureteric reflux, the recommended Bactrim (trimethoprim/sulfamethoxazole) dosing is 2-3 mg/kg of the trimethoprim component given once daily at bedtime, as supported by recent guidelines and studies 1. This dosing strategy is based on the principle of maintaining adequate urinary concentrations of the antibiotic overnight, when urine stasis is more likely to occur, thereby preventing bacterial colonization in the urinary tract. The medication should be administered consistently each evening to ensure its effectiveness. For infants under 2 months of age, Bactrim is generally avoided due to the risk of kernicterus and other adverse effects 1. The duration of prophylaxis depends on the grade of reflux, resolution on follow-up imaging, and clinical response, but typically continues until reflux resolves or surgical intervention is performed. Some key points to consider in the management of pediatric patients with vesicoureteric reflux include:

• The grade of reflux, with higher grades (III and IV) being associated with a greater risk of recurrent UTIs and renal scarring 1
• The presence of fever, bowel and bladder dysfunction, and other clinical factors that may influence the risk of recurrent UTIs and the effectiveness of prophylactic antibiotics 1
• Regular monitoring of urinalysis and urine cultures to assess the effectiveness of prophylaxis and detect breakthrough infections
• Counseling parents about potential side effects of Bactrim, including rash, gastrointestinal upset, and rare but serious adverse reactions like Stevens-Johnson syndrome. It is essential to weigh the benefits of prophylactic antibiotics against the risk of microbial resistance and to consider alternative treatment options, such as surgical correction of reflux or behavioral modification, in certain cases 1.

From the FDA Drug Label

Children: For children, the recommended dose is 750 mg/m2/day sulfamethoxazole with 150 mg/m2/day trimethoprim given orally in equally divided doses twice a day, on 3 consecutive days per week. The total daily dose should not exceed 1600 mg sulfamethoxazole and 320 mg trimethoprim.

The recommended Bactrim (trimethoprim/sulfamethoxazole) dosing for prophylaxis against urinary tract infections in pediatric patients with vesicoureteric reflux is:

• 750 mg/m2/day sulfamethoxazole
• 150 mg/m2/day trimethoprim given orally in equally divided doses twice a day, on 3 consecutive days per week, with a maximum daily dose of 1600 mg sulfamethoxazole and 320 mg trimethoprim 2.

From the Research

Vesicoureteric Reflux Pediatric Bactrim Dosing

The recommended Bactrim (trimethoprim/sulfamethoxazole) dosing for prophylaxis against urinary tract infections in pediatric patients with vesicoureteric reflux is as follows:

• 1 mg/kg body weight of trimethoprim together with 5 mg/kg of sulfamethoxazole at bedtime every other day 3
• 2 mg trimethoprim combined with 10 mg sulphamethoxazole per kg body weight daily 4

Efficacy and Safety

Studies have shown that intermittent low-dose trimethoprim-sulfamethoxazole is effective in preventing recurrent urinary infections in children with vesicoureteral reflux 3, 4

• In one study, none of the boys had a recurrence of urinary infection, while 2 of the 11 girls had a total of 7 recurrences during the prophylaxis period 3
• Another study found that co-trimoxazole in a dose of 2 mg trimethoprin combined with 10 mg sulphamethoxazole per kg body weight daily was very effective, with only six of 130 children receiving this treatment developing a reinfection 4

Laboratory Findings

Long-term use of trimethoprim-sulfamethoxazole has been found to have no significant effect on complete blood count, serum electrolytes, or creatinine in children with vesicoureteral reflux 5

• A study found no significant electrolyte, renal, or hematologic abnormalities when comparing the treatment and placebo groups 5
• The study suggests that routine monitoring of these laboratory tests in children receiving long-term trimethoprim-sulfamethoxazole prophylaxis may not be necessary 5

Resistance and Treatment

However, there is a concern about the development of resistance to trimethoprim-sulfamethoxazole in children with vesicoureteral reflux 6, 7

• One study found that there were more trimethoprim- and sulfamethoxazole-resistant E. coli cultures from patients with vesicoureteral reflux than from those without vesicoureteral reflux 6
• Another study found that treatment with trimethoprim, sulfamethoxazole, and ampicillin alone appeared to be insufficient in many cases due to high resistance rates of E. coli and other uropathogens 6