Bactrim Formulations: IV and Oral Availability
Bactrim (trimethoprim-sulfamethoxazole) is available in both intravenous and oral formulations. 1
Available Formulations
Intravenous (IV) Formulation
- IV trimethoprim-sulfamethoxazole is available and indicated for severe infections requiring parenteral therapy 1
- The recommended IV dose for severe infections is 8-12 mg/kg/day (based on trimethoprim component) divided into 4 doses, with each dose infused over 1 hour 2, 3
- For CNS infections or severe bacteremia, the dose is 5 mg/kg/dose (based on trimethoprim) IV every 8-12 hours 3
- IV administration is specifically recommended for hospitalized patients with severe infections such as pyelonephritis, Pneumocystis pneumonia, or when oral therapy is not feasible 2
Oral Formulation
- Oral trimethoprim-sulfamethoxazole is widely available in tablet and suspension forms 1, 4
- Standard adult dosing is 1-2 double-strength tablets (800mg/160mg) twice daily for most infections 5, 3
- Oral suspension formulations deliver 40mg trimethoprim/200mg sulfamethoxazole per 5mL 6
- Pediatric dosing is 8-12 mg/kg/day (based on trimethoprim component) in 2 divided doses orally 5
Clinical Transition Strategy
- After acute pneumonitis resolves, patients can transition from IV to oral therapy with the same total daily dose to complete treatment courses 2
- This IV-to-oral switch is appropriate for patients with mild to moderate disease who do not have malabsorption or diarrhea 2
Key Clinical Considerations
- Both formulations are excreted primarily in urine, requiring dose adjustment when creatinine clearance is less than 30 mL/min 1
- The drug is contraindicated in the third trimester of pregnancy and in nursing mothers due to kernicterus risk 3
- Both IV and oral forms are effective against the same spectrum of gram-positive and gram-negative bacteria 1, 4