From the Guidelines
Bactrim (sulfamethoxazole-trimethoprim) is typically dosed based on the trimethoprim component, with a standard dose of 1-2 double-strength tablets (800mg sulfamethoxazole/160mg trimethoprim) twice daily for adults, and 8-12 mg/kg/day of the trimethoprim component, divided into 2-4 doses, for children. For most adult urinary tract infections, the standard dose is one double-strength tablet twice daily for 3-5 days. For more severe infections like pneumocystis pneumonia, higher doses of 15-20mg/kg/day of the trimethoprim component, divided into 3-4 doses, are used for 14-21 days. Children are usually dosed at 8mg/kg/day of trimethoprim divided into two doses. Renal dosing adjustments are necessary for patients with creatinine clearance below 30 mL/min. Common side effects include rash, gastrointestinal upset, and photosensitivity. Patients should maintain adequate hydration while taking Bactrim and report any unusual bleeding, severe skin reactions, or persistent fever. Bactrim works by inhibiting two sequential steps in bacterial folate synthesis, making it effective against many gram-positive and gram-negative bacteria. It should be taken with a full glass of water, and patients should complete the full prescribed course even if symptoms improve before finishing 1.
Some key points to consider when prescribing Bactrim include:
- The dose and duration of treatment may vary depending on the specific infection being treated and the patient's individual needs.
- Patients with a history of sulfa allergy or other adverse reactions to Bactrim should be monitored closely for signs of an allergic reaction.
- Bactrim may interact with other medications, such as warfarin and phenytoin, and patients should be advised to report any changes in their medication regimen.
- Patients with renal impairment may require dose adjustments to avoid toxicity.
- Bactrim is effective against a wide range of bacterial infections, including urinary tract infections, respiratory tract infections, and skin and soft tissue infections.
Overall, Bactrim is a effective and widely used antibiotic that can be used to treat a variety of bacterial infections, but it should be used judiciously and with careful consideration of the patient's individual needs and medical history 1.
From the FDA Drug Label
The usual adult dosage in the treatment of urinary tract infections is 1 sulfamethoxazole and trimethoprim tablet (double strength) or 2 sulfamethoxazole and trimethoprim tablets (400 mg/80 mg) 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 1 44 20 1 66 30 1½ 88 40 2 (400 mg/80 mg) or 1 (DS) tablet 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 30 Usual standard regimen 15-30 ½ the usual regimen Below 15 Use not recommended
The dosing for Trimethoprim-Sulfamethoxazole (Bactrim) is as follows:
- Adults: 1 double strength tablet or 2 single strength tablets every 12 hours for 10 to 14 days for urinary tract infections
- Children: 40 mg/kg sulfamethoxazole and 8 mg/kg trimethoprim per 24 hours, given in two divided doses every 12 hours for 10 days
- Renal impairment: reduced dosage for creatinine clearance 15-30 mL/min, and not recommended for creatinine clearance below 15 mL/min 2 3
From the Research
Dosing for Trimethoprim-Sulfamethoxazole (Bactrim)
- The dosing for Trimethoprim-Sulfamethoxazole should be adjusted when the creatinine clearance decreases to less than 30 ml/min 4, 5, 6
- A daily dose of 320/1,600 mg of Trimethoprim-Sulfamethoxazole was highly effective for prophylaxis in renal transplantation patients 7
- A dose of 160/800 mg daily of Trimethoprim-Sulfamethoxazole gave unexpectedly low blood levels and was effective only for prevention of urinary tract infections after catheter removal 7
- Trimethoprim-Sulfamethoxazole (160:800 mg) twice daily for 7 days was used for the treatment of acute uncomplicated cystitis in women 8