C difficile risk
Oral Bioavailability


Routine Indications:

  • 1- 2 double strength (DS) tabs PO BID (Note: 1 DS tab = 160 mg trimethoprim, 800 mg sulfamethoxazole)

  • IV: 8 to 20 mg/kg/day (TMP component) divided every 6 to 12 hours.

Infuse over 60 minutesNot for use in infants <1 month of age; contains TMP/SMX in ratio of 1:5

Minor InfectionsProphylaxis (UTI)Serious Infections4mg (TMP)/kg/dose PO Q12H0.5 to 1mg (TMP)/kg PO once daily5mg (TMP)/kg/dose IV Q6-8H


IV: 1.6 mg/mL (as trimethoprim)

Mix 18mL of D5W with 2mL of undiluted trimethoprim/sulfamethoxazole in a 30mL empty sterile vial = 1.6 mg/mL (as trimethoprim)PREPARE JUST PRIOR TO ADMINISTRATION

16 mg/mL (trimethoprim) = 48H (after first use) 1.6 mg/mL (trimethoprim) = 1.5HRoom Temperature DO NOT REFRIGERATE

0 - 30 eGFR30+ eGFR- 1 - 2 DS tab daily OR

  • If normal dose is 1 DS tab BID: 1 DS tab followed by 1 SS tab BID

  • If normal dose is 2 DS tab BID: 1 DS tab BIDNo dosage adjustment required.

Depends on indication and and originally recommended dose. Consult pharmacy.

Neonatal: Reduce dose in liver impairment

General Information

Urinary tract infections, skin and soft tissue infections, pulmonary infections, bone and joint infections, meningitis, susceptible MRSA infections, Stenotrophomonas infections, Pneumocystis jirovecii pneumonia (treatment or prophylaxis), Nocardia infections

Pregnancy: An increased risk of congenital malformations (neural tube defects, cardiovascular malformations, urinary tract defects, oral clefts, club foot) following maternal use of sulfamethoxazole and trimethoprim during pregnancy has been observed in some studies. Folic acid supplementation should be considered if used during the first trimester. Use during the first trimester should be limited to situations where no alternative therapies are available. Due to theoretical concerns that sulfonamides pass the placenta and may cause kernicterus in the newborn, alternatives can be considered at the time of delivery, though there have not been any cases reported with exposure in utero.

Breastfeeding: Sulfamethoxazole and trimethoprim are both present in breastmilk. A systematic review of the use of sulfonamides near term and during breastfeeding found no adverse reactions in infants. However, caution in jaundiced, ill, stressed or premature infants, because of the possible risk of bilirubin displacement and kernicterus (thought this has never been reported via breastmilk exposure). Breastfeeding is likely compatible in healthy, fullterm infants. Monitor for signs of jaundice. Sulfamethoxazole and trimethoprim should be avoided while breastfeeding a G6PD-deficient infant.

Serum creatinine, potassium, BUN in patients at increased risk renal failure or hyperkalemia CBC

Stevens Johnson syndrome/toxic epidermal necrolysis, other rashes, gastrointestinal upset common, bone marrow suppression, thrombocytopenia, hyperkalemia, renal failure, hepatitis, aseptic meningitis, systemic lupus erythematosus (rare)

  • ACEi - increased serum potassium level

  • Increases amantadine levels

  • Decreases cyclosporine

  • Methotrexate - marrow suppression

  • Increases phenytoin

  • Increases rifampin

  • Increases INR with warfarin

High dose therapy required for treatment of Pneumocystis pneumonia and Stenotrophomonas maltophilia infections.

Use with caution in patients with G6PD deficiency; hemolysis may occur (dose-related). Use with caution in patients with potential folate deficiency. Use with caution in patients with systemic lupus erythematosus.

Antimicrobial class: Sulfonamide - Antifolate.