Disclaimer to the On-line Edition
This Manual has been designed for use in the NICU at London Health Sciences Centre (LHSC), London, Ontario, Canada, and represents clinical practice at this institution. The information contained within the Manual may not be applicable to other centres. If users of this Manual are not familiar with a drug, it is recommended that the official monograph be consulted before it is prescribed and administered. Any user of this information is advised that the contributors, Editor and LHSC are not responsible for any errors or omissions, and / or any consequences arising from the use of the information in this Manual.



  • Prophylaxis of urinary tract infections (UTI) in newborns with structural anomalies of the genitor-urinary tract


Trimethoprim (TMP) inhibits the enzyme dihydrofolate reductase (DHFR). DHFR catalyzes the reduction of dihydrofolate to tetrahydrofolate. Tetrahydrofolate is the active form of folic acid and is required in the biosynthesis of nucleic acids. TMP possesses a wide spectrum of activity against both gram positive and gram negative organisms.

Side Effects

Rash, hyperkalemia, hyponatremia, elevated liver enzymes, nausea, vomiting, elevated BUN and serum creatinine


1 mg/kg po q12h

(The rationale for giving trimethoprim in one evening dose is the long overnight dwell in the bladder in older children. Babies have no bladder control and just cycle the bladder when the intravesical pressure exceeds the opening pressure.)


10 mg/mL suspension (prepared with simple syrup - 85 % sucrose)
Stable for 30 days at Room temp
SHAKE WELL before using


  1. "Trimethoprim" in Lexi-Comp Online, accessed 18 Dec 2009.
  2. "Trimethoprim" in Micro Medex Online, accessed 18 Dec 2009.

Prepared by David Knoppert, Dec 2009
Reviewed by Dr Guido Filler, Dec 2009

Last Uploaded: Thursday, 26-May-2011 00:53:49 EDT