Recommended Dosage of Injection Trimethoprim Sulphamethoxazole for Adults
For adult patients, the recommended intravenous dosage of Trimethoprim-Sulfamethoxazole (TMP-SMX) is trimethoprim 320 mg per day and sulfamethoxazole 1,600 mg per day, divided into 2 doses and administered every 12 hours. 1
Standard Dosing Regimens
The dosage of TMP-SMX injection varies based on the indication:
For Pneumocystis jirovecii Pneumonia (PCP):
- 15-20 mg/kg/day of trimethoprim component divided in 3 or 4 equal doses (every 6 to 8 hours) for 14 days 2
- This higher dosage is necessary for effective treatment of this severe opportunistic infection
For Severe Urinary Tract Infections:
- 8-10 mg/kg/day of trimethoprim component divided in 2 to 4 equal doses (every 6,8, or 12 hours) for 14 days 2
For Shigellosis:
- 8-10 mg/kg/day of trimethoprim component divided in 2 to 4 equal doses (every 6,8, or 12 hours) for 5 days 2
Administration Guidelines
TMP-SMX injection requires proper dilution and administration:
- Each 5 mL of TMP-SMX injection should be diluted in 125 mL of 5% dextrose in water 2
- The solution should be administered by intravenous infusion over 60-90 minutes 2
- Rapid infusion or bolus injection should be avoided to prevent adverse reactions 2
- After dilution, the solution should be used within 6 hours and should not be refrigerated 2
- For patients requiring fluid restriction, a more concentrated dilution (5 mL per 75 mL of 5% dextrose) may be used, but must be administered within 2 hours 2
Dosage Adjustments for Renal Impairment
Renal function significantly impacts TMP-SMX clearance, requiring dosage adjustments:
- Normal renal function: Standard dosage as above 2
- Creatinine clearance 15-30 mL/min: Reduce to half the usual dosage regimen 2
- Creatinine clearance below 15 mL/min: TMP-SMX injection is not recommended 2
The half-lives of both TMP and SMX increase with age and are directly correlated with serum creatinine levels, necessitating careful monitoring in elderly patients or those with impaired renal function 3
Monitoring and Adverse Effects
Common adverse effects that require monitoring include:
- Gastrointestinal effects (nausea, vomiting) 1
- Hypersensitivity skin reactions 1
- Blood dyscrasias (monitor complete blood counts) 1
- Thrombocytopenia (associated with higher serum TMP levels and longer treatment duration) 3
Special Considerations
- TMP-SMX is contraindicated in patients with known hypersensitivity to trimethoprim or sulfonamides 2
- The medication should be used with caution in patients with impaired hepatic function, folate deficiency, or blood dyscrasias 1
- TMP-SMX should not be administered to pregnant women, nursing mothers, or infants aged <2 months due to potential risk for kernicterus 1
- Adequate fluid intake should be maintained to prevent crystalluria and renal stones 1
Stability Information
TMP-SMX injection is stable in glass containers with various infusion fluids for up to 12 hours at room temperature 4. If cloudiness or crystallization occurs after mixing, the solution should be discarded and a fresh solution prepared 2.