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

From the Guidelines

Trimethoprim-sulfamethoxazole (TMP-SMX) dosing for uncomplicated urinary tract infections is 1 double-strength tablet (160mg TMP/800mg SMX) twice daily for 3 days, as recommended by the most recent and highest quality study 1.

Key Considerations

• The dosing may vary based on the infection being treated, with more severe infections requiring higher doses or longer treatment durations.
• For patients with renal impairment, dosing should be adjusted, with frequency reductions when creatinine clearance falls below 30 mL/min.
• TMP-SMX works by inhibiting two sequential steps in bacterial folate synthesis, making it effective against many gram-positive and gram-negative bacteria.
• Common side effects include rash, gastrointestinal disturbances, and hyperkalemia, and patients should be monitored for allergic reactions, especially those with sulfa allergies.

Evidence Summary

• A 2021 study published in the Annals of Internal Medicine 1 recommends TMP-SMX as a first-line treatment for uncomplicated urinary tract infections, with a dosing regimen of 1 double-strength tablet twice daily for 3 days.
• Other studies, such as those published in Clinical Infectious Diseases 1, also support the use of TMP-SMX for urinary tract infections, but the 2021 study provides the most recent and highest quality evidence.

Important Notes

• The medication should be taken with plenty of water to reduce the risk of adverse effects.
• Patients with a history of sulfa allergies should be monitored closely for signs of an allergic reaction.
• TMP-SMX is not recommended for patients with severe renal impairment or those who are pregnant or breastfeeding, unless the benefits outweigh the risks.

From the FDA Drug Label

DOSAGE AND ADMINISTRATION Not recommended for use in pediatric patients less than 2 months of age. Urinary Tract Infections and Shigellosis in Adults and Pediatric Patients, and Acute Otitis Media in Children Adults: The usual adult dosage in the treatment of urinary tract infections is 1 sulfamethoxazole and trimethoprim DS tablet every 12 hours for 10 to 14 days An identical daily dosage is used for 5 days in the treatment of shigellosis. 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. For Patients With Impaired Renal Function When renal function is impaired, a reduced dosage should be employed using the following table: Creatinine Clearance (mL/min)Recommended Dosage Regimen Above 30Usual standard regimen 15-301/2 the usual regimen Below 15Use not recommended Acute Exacerbations of Chronic Bronchitis in Adults The usual adult dosage in the treatment of acute exacerbations of chronic bronchitis is 1 sulfamethoxazole and trimethoprim double strength tablet every 12 hours for 14 days Pneumocystis Carinii Pneumonia Treatment Adults and Children: The recommended dosage for patients with documented Pneumocystis carinii pneumonia is 75 to 100 mg/kg sulfamethoxazole and 15 to 20 mg/kg trimethoprim per 24 hours given in equally divided doses every 6 hours for 14 to 21 days Prophylaxis Adults The recommended dosage for prophylaxis in adults is 1 sulfamethoxazole and trimethoprim DS (double strength) tablet daily 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. Travelers’ Diarrhea in Adults For the treatment of traveler’s diarrhea, the usual adult dosage is 1 sulfamethoxazole and trimethoprim DS (double strength) tablet or 2 sulfamethoxazole and trimethoprim tablets every 12 hours for 5 days.

The dosing for Trimethoprim (TMP)-Sulfamethoxazole (SMZ) varies based on the condition being treated.

• Urinary Tract Infections and Shigellosis:
  • Adults: 1 DS tablet every 12 hours for 10 to 14 days
  • Children: 40 mg/kg sulfamethoxazole and 8 mg/kg trimethoprim per 24 hours, given in two divided doses every 12 hours for 10 days
• Acute Exacerbations of Chronic Bronchitis:
  • Adults: 1 DS tablet every 12 hours for 14 days
• Pneumocystis Carinii Pneumonia:
  • Adults and Children: 75 to 100 mg/kg sulfamethoxazole and 15 to 20 mg/kg trimethoprim per 24 hours given in equally divided doses every 6 hours for 14 to 21 days
• Prophylaxis:
  • Adults: 1 DS tablet daily
  • Children: 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
• Travelers’ Diarrhea:
  • Adults: 1 DS tablet or 2 tablets every 12 hours for 5 days 2

From the Research

Dosing for Trimethoprim (TMP)-Sulfamethoxazole (SMZ)

• The dosing for Trimethoprim (TMP)-Sulfamethoxazole (SMZ) varies depending on the specific condition being treated and the patient population 3, 4, 5, 6, 7.
• For healthy, adult, nonpregnant women with bacterial cystitis, 3 days of trimethoprim/sulfamethoxazole (TMP/SMZ) is standard therapy in those regions where less than 10% to 20% of Escherichia coli that cause such infections is resistant to TMP/SMZ 3.
• For children, intravenous TMP-SMZ was given at a daily dose of 10 and 50 mg/kg, respectively, every six hours 4.
• For women hospitalized with acute pyelonephritis, TMP/SMZ was given at 160/800 mg iv every 12 h for 3 days, then 160/800 mg orally twice daily 5.
• For single-dose therapy in women with urinary tract infection, a single dose of two double-strength trimethoprim-sulfamethoxazole tablets (320 mg of TMP and 1,600 mg of SMZ) was used 6.
• For intravenous administration in children and adults with normal and impaired renal function, a loading dose of 250 mg of TMP and 1,250 mg of SMZ/m2 is recommended, 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 7.

Special Considerations

• In regions where resistance to TMP/SMZ is more than 10% to 20%, alternative treatments such as oral fluoroquinolones or nitrofurantoin may be recommended 3.
• Patients with renal failure may require adjusted dosing intervals, with the dosage interval (hr) increased to 12 times the serum creatinine level (mg/dl) (maximum, 48 hr) 7.
• Serum concentrations of TMP and perhaps of N4-acetyl-SMZ should be monitored in patients with severe renal failure 7.