Parenteral Manual

Sulfamethoxazole and Trimethoprim

Disclaimer: Official controlled document is the CHEO online copy. It is the responsibility of user to ensure that any paper copy version is the same as the online version before use.

Alternate Name(s): 
Original Date: 
August 2005
Revised Date: 
November 2017
  • Treatment of infections due to susceptible gram positive and gram negative bacteria     
  • Treatment of Pneumocystis carinii pneumonia (PCP).
Reconstitution and Stability: 
  • Available as ampoules containing 16 mg/mL Trimethoprim and 80 mg/mL sulfamethoxazole
  • All doses, dilutions based on the trimethoprim [TMP] component
  • Protect from light.  Keep at room temperature, do not refrigerate                                  
  • MUST be diluted prior to use                     
  • Diluted with D5W to a concentration of 0.64 mg/mL of TMP stable 48 hrs 
  • Diluted with D5W to a concentration of 0.8 mg/mL of TMP stable 24 hrs  
  • Diluted with D5W to a concentration of 1 mg/mL of TMP stable 2 hours
  • Diluted with D5W to a concentration of 1.6 mg/mL of TMP stable 1 hour

- Solutions Compatible: D5W

- Additives/Above Cassette Compatible: no information

- Y-site Compatible: morphine

- Incompatible: TPN, 0.9% NaCl (compatible with 0.9% NaCl) but over time, a precipitate forms. Therefore, D5W is the preferred solution)


(For approved routes of administration by nursing personnel, refer to Policy for the Administration of Intravenous Medications.)

IV Direct


IV Intermittent Infusion YES

Syringe pump dilution: 0.8 mg/mL of TMP ONLY


Large volume pump

Usual dilution: 0.64 to 0.8 mg/mL of TMP preferred dilution
Fluid restricted patients: 1 to 1.6 mg/mL of TMP

Infusion time: 1 to 1.5 hours

IV Continuous Infusion NO

(For neonatal dosages, refer to Neonatal IV Drug Manual.)

  • Based on Trimethoprim [TMP] component


  • Bacterial Infection: 8-12 mg TMP/kg/day IV ÷ Q 12 hours
  • Pneumocystis carnii: 20 mg TMP/kg/day IV ÷ Q 6 hours
  • Pneumocystitis carinii prophylaxis: 150 mg TMP/m2/day IV÷ Q 12-24 hours 3 days/week Maximum: 320 mg TMP/day

Adjustment for Renal Impairment:

  • CrCl > 30 mL/minute: Standard regimen
  • CrCl 15-30 mL/minute: Reduce dose by 50%
  • CrCl < 15 mL/minute: Not recommended
Potential hazards of parenteral administration: 
  • Thrombophlebitis, pain and local irritation at site of injection    
  • Rare fatalities have occurred due to severe Stevens-Johnson syndrome, toxic epidermal necrolysis, hepatic necrosis, agranulocytosis, aplastic anemia and other blood dyscrasias; discontinue use at first sign of rash or any sign of adverse reaction
  • Nausea, vomiting
  • Mild and reversible increase in serum creatinine
  • Hyperkalemia
  • Avoid in infants <2 months of age
  • Allergy - avoid in patients with known hypersensitivity to trimethoprim or sulfonamides
  • Avoid in patients with megaloblastic anemia due to folate deficiency
  • Fluid overload is a possible complication of large doses of cotrimoxazole
  • Use with caution in G-6-PD deficiency, impaired renal or hepatic function
  • Monitor blood counts in patients predisposed to folate deficiency (malnutrition states, malabsorption syndromes and anticonvulsant therapy)
  • May potentiate the effects of oral anticoagulants (e.g. Warfarin)
  • Decreases serum cyclosporin levels                                                    
  • Injection contains propylene glycol 40%, ethanol 10%, benzyl alcohol 1%, diethanolamine 0.3% and sodium metabisulfite 0.1%                    
  • Maintain adequate fluid intake to prevent crystalluria and stone formation
  • Increases the effect of phenytoin, digoxin and thiopental

The information contained on this website is provided for informational purposes only, as a guide to assist physicians, nurses and other healthcare providers in deciding on the appropriate care required for a particular patient. At all times, physicians, nurses and other healthcare providers must exercise their independent clinical judgment, based on their knowledge, training and experience, taking into account the specific facts and circumstances of each patient, when deciding on the appropriate course of investigation and/or treatment to recommend in a particular clinical situation.

CHEO has made every effort to ensure that the information contained on this website is as current and accurate as possible. However, changes can occur due to ongoing research and the constant influx of new information. Where possible, hospitals and healthcare practitioners should verify the information before acting on it.

Reliance on any information in this website is at the user's own risk. CHEO is not responsible or liable for any harm, loss or other consequences from the use or misuse of the information on this website.