C difficile risk
Oral Bioavailability
IV: $$$ PO: $ (Tablet)

Spectrum Of Activity


Treatment4-6 mg TMP/kg/dose PO/IV q12h (includes 20-30 mg/kg/dose sulfamethoxazole)

Treatment of suspected or proven infectionProphylaxis in Haematology/Oncology/HPCT PatientsHIV-infected/exposed children ≤12 yrsHIV-infected/exposed children >12 yrsAlternative regimens for HIV-infected/exposed childrenOther immunocompromised children5 mg trimethoprim/kg/dose IV/PO q6h (includes 25 mg/kg/dose sulfamethoxazole)150mg TMP/m2/day
(5mg/kg/day) PO as a single daily dose or divided BID on 2-3 consecutive days/week
Dose limit: 320 mg TMP/day for 2-3x/weekly regimenUsual dosing is 75mg/m2 PO q12h every Friday, Saturday, Sunday 5 mg TMP/kg/dose PO once daily (preferred regimen for improved compliance) Dose limit: 160 mg TMP/day1 single strength (SS) tablet (80mg TMP/400mg SMX) PO once daily (preferred regimen for improved compliance)

  • ≤12 yrs: 2.5 mg TMP/kg/dose PO q12h, 3 times weekly

  • 12 yrs: 1 double strength (DS) tablet (160mg TMP/800mg SMX) PO daily 3 times weekly2.5-5 mg TMP/kg/day PO as a single daily dose, given 3 times weekly Round to the nearest tablet size Dose limit: 160mg TMP/day

TreatmentProphylaxis4-6 mg TMP/kg/dose PO q12h (includes 20-30 mg/kg/dose SMX)2-5 mg trimethoprim/kg/dose PO once daily Dose limit: 320mg TMP/day (160mg TMP/dose) Trimethoprim alone (without SMX) may be preferred as UTI prophylaxis for some patients, i.e. infants <1 month of age, or patients in whom an oral suspension is preferred


General Information

Pneumonia in an Immunocompromised Host:

  • TMP-SMX may not be appropriate if significant neutropenia or post-BMT and not yet engrafted

Cutaneous Abscesses, Furuncles, Carbuncles, and Boils (with or without cellulitis):

  • If there are risk factors for MRSA or failed 1st-line outpatient treatment despite adequate adherence:

    • PO: TMP-SMX or Clindamycin or Doxycycline (if ≥ 8 yrs old)
  • Use Clindamycin or Doxycycline if Group A strep is strongly suspected despite failure of 1st-line treatment

  • TMP-SMX does not cover Streptococcal infections well

ODB covered (tablet)

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

  • CBC, renal function test, liver function test, urinalysis; observe for change in bowel frequency

  • Sulfa antibiotics have been shown to displace bilirubin from protein binding sites which may potentially lead to hyperbilirubinemia and kernicterus in neonates and young infants; do not use in neonates; avoid use in infants <2 months unless other options are not available (eg, Pneumocystis)

May be taken with or without food

  • Maintain fluid intake. May be given with food

  • Do not give to infants <1 month old due to risk of kernicterus

  • Special Access Program authorization required for suspension, which is no longer marketed in Canada

  • Brand names: Cotrimoxazole, Septra, Bactrim

  • Trimethoprim and Sulfamethoxazole (TMP/SMX) is available in combination as a fixed dose ratio of 1:5