(Trimethoprim/Sulfamethoxazole [TMP/SMX]) (Bactrim, Septra)


  • Antibiotic


  • Combination antibiotic (sulfonamide and folate antagonist)


  • Urinary tract infections (pyelonephritis, cystitis) (E. coli, Klebsiella and Enterobacter species, M. morganii, P. mirabilis, P. vulgaris)

  • Shigella enteritis (S. flexneri, S. sonnei)

  • Pneumocystis carinii pneuomonia

  • Acute otitis media (children) (H. influenzae, S. pneumoniae)

  • Acute exacerbations of chronic bronchitis (adults) (H. influenzae, S. pneumoniae)

  • Travelerís diarrhea (E. coli)

  • Acute and chronic pancreatitis

  • Unlabeled uses:

  • Cholera

  • Salmonella-type infections

  • Nocardiosis


  • Hypersensitivity to sulfa-related medications (sulfonylureas, thiazide and loop diuretics, carbonic anhydrase inhibitors, sunscreens with PABA, local anesthetics)

  • Pregnancy at term

  • Lactation

  • Infants less than 2 months old (except congenital toxoplasmosis as adjunct with pyrimethamine)

  • Megaloblastic anemia caused by folate deficiency


  • Pregnancy category C

  • Sulfonamides have been associated with severe hypersensitivity reactions and death.

  • Serious blood disorders (agranulocytosis, hepatocellular necrosis, aplastic anemia) have been associated with sulfonamides.  Perform complete blood counts.  Symptoms of sore throat, fever, pallor, purpura or jaundice may be early signs of serious blood disorders.

  • Use with caution in patients with severe asthma or allergies.

  • Hemolytic anemia may occur in patients with G-6-PD deficiency.

  • Photosensitization may occur, caution patients to use protective measures against ultraviolet or sunlight until tolerance is determined.

  • Sulfonamides increase the effect of oral anticoagulants (warfarin).

  • Take with a full glass of water and increase fluid intake to 2-3 liters per day.

  • Complete full course of therapy.

  • Parenteral therapy may cause extravascular infiltration and local irritation.

  • For oral suspension; store at room temperature, shake well before using

Adverse Reactions (Side Effects):

  • Headache, peripheral neuropathy, depression

  • Tinnitis, vertigo

  • Nausea, emesis, abdominal pain, anorexia, diarrhea

  • Hepatitis, pancreatitis, stomatitis

  • Urticaria, Stevens-Johnson type erythema multiforme

  • Crystalluria, elevated creatinine

  • Drug fever, chills

  • Photosensitivity 


Administered orally (tablets and suspension) and IV injection

  • Urinary tract infections, shigellosis, acute otitis media:

    • Adults: 160mg TMP and 800mg SMX q12h for 10-14 days (shigellosis for 5 days)

    • Children (> 2months): 8mg/kg TMP and 40mg/kg SMX in divided doses q12h for 10 days (shigellosis for 5 days)

  • Travelerís diarrhea:

    • Adults: 160mg TMP and 800mg SMX q12h for 5 days

  • Acute exacerbations of chronic bronchitis

    • Adults: 160mg TMP and 800mg SMX q12h for 14 days

  • Pneumocystis carinii pneumonia:

    • Adults: 15-20 mg/kg TMP and 100mg/kg SMX in divided doses q6h for 14-21 days

  • Parenteral:

    • Adults and Children > 2 months: 15-20 mg/kg/day (based on TMP dose) in 3-4 divided doses q6-8h for up to 14 days

  • Prophylaxis:

    • Adults: 160mg TMPO and 800mg SMX given orally q24h

    • Children > 2 months: 150mg/m2 TMP and 750mg/m2 SMX given orally in equally divided doses twice a day on three consecutive days of the week (do not exceed 320mg TMP and 1600mg SMX per day)

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