Sulfamethoxazole

Sulfamethoxazole, as a sulfonamide, works by inhibiting bacterial dihydrofolate synthesis. When combined with trimethoprim, it exhibits synergistic activity through sequential blockade of the bacterial folate synthesis pathway, leading to an enhanced antibacterial effect.

Adult

Treatment of susceptible infections: By mouth, 960 mg twice daily; By intravenous infusion, 960 mg every 12 hours, increased to 1.44 g every 12 hours in severe infection. Moderate/Severe diabetic foot infection: By mouth, 960 mg twice daily; By intravenous infusion, 960 mg every 12 hours, increased if necessary to 1.44 g every 12 hours.…

Pediatric

Child 6 weeks–5 months: 120 mg twice daily, alternatively 24 mg/kg twice daily. Child 6 months–5 years: 240 mg twice daily, alternatively 24 mg/kg twice daily. Child 6–11 years: 480 mg twice daily, alternatively 24 mg/kg twice daily. Child 12–17 years: 960 mg twice daily.

Renal adjustment

Usual initial dose, then use half normal dose if eGFR 20–50 mL/minute/1.73 m2; 100 mg every 24 hours if eGFR less than 20 mL/minute/1.73 m2.

Hepatic adjustment

Manufacturer advises caution; maximum 400 mg daily in hepatic failure (risk of decreased elimination).

• risk of crystalluria