Injectable Cotrimoxazole Dosing in mL
The usual dose of injectable cotrimoxazole is calculated as 5-10 mL per dose (equivalent to 400-800 mg trimethoprim component) given every 6-12 hours for adults, with the standard ampule containing 80 mg trimethoprim/400 mg sulfamethoxazole per 5 mL.
Standard Adult Dosing
The dosing of injectable cotrimoxazole depends on the severity of infection and indication:
For Severe Infections
- Standard severe infection dosing: 10 mL (2 ampules) every 12 hours, equivalent to 160 mg trimethoprim/800 mg sulfamethoxazole per dose 1
- For documented MRSA pneumonia: 5 mg/kg/dose IV every 8-12 hours, which translates to approximately 7.5-15 mL per dose for a 70 kg adult 1
- High-dose regimen for CNS infections: Up to 20 mL (4 ampules) twice daily has been used safely in neurosurgical patients without toxicity 2
For Moderate Infections
- Standard moderate infection dosing: 5-10 mL (1-2 ampules) every 12 hours 3
Pediatric Dosing Considerations
For children requiring IV therapy:
- Dose calculation: 8-12 mg/kg/day of trimethoprim component, divided every 6-12 hours 4, 5
- For severe pneumonia: 15-20 mg/kg/day trimethoprim divided every 6-8 hours 4
- Contraindication: Never use in infants under 2 months due to kernicterus risk 5
Renal Dose Adjustments
Critical adjustments are required for impaired kidney function:
- CrCl 15-30 mL/min: Reduce dose by 50% 4
- CrCl <15 mL/min: Reduce dose by 50% or use alternative agent 4
- Hemodialysis patients: Give 50% of dose after each dialysis session 4
Important Clinical Caveats
Contraindications and Monitoring
- Absolute contraindications: G6PD deficiency (hemolytic anemia risk), known sulfonamide hypersensitivity 4, 5
- Mandatory monitoring: Obtain baseline complete blood count and repeat monthly during prolonged therapy to detect thrombocytopenia, neutropenia, or anemia 1, 5
- Stevens-Johnson syndrome risk: Though rare, this devastating complication must be discussed with patients before initiating therapy 6
Drug Interactions
- Avoid concurrent methotrexate at treatment doses due to severe bone marrow suppression risk 1
- Caution with warfarin: May potentiate anticoagulant effects 5
Practical Administration Notes
Each standard ampule of injectable cotrimoxazole contains 80 mg trimethoprim/400 mg sulfamethoxazole in 5 mL 2. The medication requires dilution before IV administration and should be infused over 60-90 minutes to minimize vein irritation 3.