C difficile risk
Oral Bioavailability


Usual dose: Infants ≥2 months, Chidren, and Adolescents: Oral, IV: 6 to 12 mg TMP/kg/DAY divided q12h; Maximum: 320 mg TMP/DAY.

Note dosing is expressed in mg of trimethoprim component.

Meningitis/PJP infection: IV: 15-20 mg TMP/kg/DAY divided q6-12h

Use caution in infants <2 months old due to risk of kernicterus. No dosing references available.

Renally cleared, requires dosage adjustment with changes in renal function. Consult a pharmacist for renal dosing.

PJP prophylaxis in immunocompromised patients: 5 mg TMP/kg/DAY or 150 mg/m2/DAY PO given as a single daily dose or divided q12h for 2-7 days per week UTI prophylaxis: 2 mg TMP/kg/DAY given as a single daily dose.

General Information

Urinary tract infections, susceptible MRSA infections, Stenotrophomonas infections, Pneumocystis jirovecii pneumonia (treatment or prophylaxis)

Follow creatinine and electrolytes in patients at increased risk renal failure, hyperkalemia, CBC for cytopenias.

Stevens Johnson syndrome/toxic epidermal necrolysis, other rashes, gastrointestinal upset common, bone marrow suppression, hyperkalemia, renal failure, hepatitis, aseptic meningitis

  • ACEi - increased serum potassium level

  • Methotrexate- marrow suppression

  • Increases phenytoin <br>Increases INR with warfarin

  • Pediatric strength tablets 100mg SMX/ 20 mg TMP.

  • Regular strength tablets 400mg SMX/ 80 mg TMP.

  • Double strength tablets 800 mg SMX/ 160mg TMP

Antimicrobial class: Sulfonamide - Antifolate

Average serum half life:

  • TMP (prolonged in renal failure)

    • Newborns: ~19 hours; range: 11-27 hours
    • infants 2 months to 1 year: ~4.6 hours; range: 3-6 hours.
    • Children 1-10 years: 3.7-5.5 hours.
    • Children and Adolescents >10 years: 8.19 hours
    • Adults: 6-11 hours
  • SMX: 9-12 hours, prolonged in renal failure (Adult data)

Route of Elimination: Both excreted in urine as metabolites and unchanged drug