What is the appropriate dosage of Bactrim (trimethoprim/sulfamethoxazole) to prescribe?

From the Guidelines

The recommended dosage of Bactrim (trimethoprim/sulfamethoxazole) for adults is 1-2 double-strength tablets (160 mg trimethoprim/800 mg sulfamethoxazole) every 12 hours, as indicated in the treatment guidelines for skin and soft-tissue infections 1. For children, the dosage is typically 8-12 mg/kg/day (based on the trimethoprim component) divided into two doses, as stated in the guidelines for MRSA SSTI treatment 1. The choice of dosage depends on the severity of the infection, patient factors, and local epidemiology. Key considerations include:

• The need for adequate hydration to prevent crystalluria
• Dosage adjustments for patients with renal impairment, with frequency reduction recommended when creatinine clearance falls below 30 mL/min
• The potential for resistance and the importance of selecting the appropriate antibiotic based on local susceptibility patterns
• The use of Bactrim as part of a comprehensive treatment plan, which may include incision and drainage for abscesses and other supportive care measures. In general, Bactrim is effective against a wide range of bacterial pathogens, including MRSA, and is a useful option for the treatment of skin and soft-tissue infections, as well as other types of infections, as supported by the guidelines 1.

From the FDA Drug Label

The usual adult dosage in the treatment of urinary tract infections is 1 sulfamethoxazole and trimethoprim double strength tablet or 2 sulfamethoxazole and trimethoprim tablets every 12 hours for 10 to 14 days 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 10 - 44 20 1 66 30 1½ 88 40 2 or 1 DS tablet

The appropriate dosage of Bactrim (trimethoprim/sulfamethoxazole) to prescribe is:

• For adults: 1 double strength tablet or 2 single strength tablets every 12 hours for 10 to 14 days for urinary tract infections.
• For children: 40 mg/kg sulfamethoxazole and 8 mg/kg trimethoprim per 24 hours, given in two divided doses every 12 hours for 10 days, with the dose adjusted according to the child's weight as shown in the provided table 2.

From the Research

Bactrim Dosage

The appropriate dosage of Bactrim (trimethoprim/sulfamethoxazole) to prescribe can vary depending on the specific condition being treated.

• For uncomplicated skin infections, a study found that trimethoprim-sulfamethoxazole (TMP-SMX) was effective in treating skin and skin-structure infections, including cellulitis and abscesses, with a dosage of 160 mg/800 mg twice daily for 10 days 3.
• Another study compared the efficacy of a higher dose of TMP-SMX (320 mg/1,600 mg twice daily) to the standard dose (160 mg/800 mg twice daily) for 7 to 15 days in patients with skin and soft tissue infections caused by methicillin-resistant Staphylococcus aureus (MRSA), and found that the higher dose did not result in a significantly higher rate of clinical resolution 4.
• A study on the pharmacokinetics of TMP-SMX in the elderly found that the dosage of 160 mg/800 mg twice daily resulted in higher plasma concentrations of trimethoprim in elderly patients compared to younger patients, but the clinical significance of this finding is unclear 5.
• The standard dosage of Bactrim for various infections, including urinary tract infections, bacterial upper respiratory tract infections, and skin and soft-tissue infections, is typically 160 mg/800 mg twice daily 6.
• A study comparing cephalexin plus trimethoprim-sulfamethoxazole to cephalexin alone for the treatment of uncomplicated cellulitis found that the combination therapy did not result in a higher rate of clinical cure, but the dosage of trimethoprim-sulfamethoxazole used was 320 mg/1,600 mg twice daily 7.

Considerations for Dosage

When prescribing Bactrim, consider the following:

• The dosage may need to be adjusted in patients with renal impairment, as trimethoprim is primarily excreted by the kidneys 5.
• The efficacy and safety of Bactrim in patients with certain medical conditions, such as liver disease or allergies to sulfonamides, should be carefully evaluated 6.