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Antimicrobials
Trimethoprim/Sulfamethoxazole

Trimethoprim/Sulfamethoxazole

Medium
Good (70 to 90%)
IV: $8.26/dose; PO: $0.05/DS tablet

Dosing

General Information

  • Serum creatinine

  • Potassium

  • CBC

  • LFTs

  • Gastrointestinal upset

  • Bone marrow suppression

  • Hyperkalemia

  • Increased serum creatinine

  • Drug-induced liver injury

  • Skin reactions, including Stevens-Johnson syndrome/toxic epidermal necrolysis

Bactrim, Bactrim-DS

  • Absorption: Oral: Rapid; almost completely (90% to 100%)
  • Distribution: 
    • Both SMX and TMP distribute to middle ear fluid, sputum, vaginal fluid
    • TMP also distributes into bronchial secretions
    • Vd = 1.3 L/kg
  • Protein Binding: 
    • SMX: ~70%
    • TMP: ~44%
  • Metabolism: 
    • Hepatic, both to multiple metabolites
    • SMX to hydroxy (via CYP2C9) and acetyl derivatives, and also conjugated with glucuronide; TMP to oxide and hydroxy derivatives
    • The free forms of both SMX and TMP are therapeutically active
  • Half-Life Elimination: 
    • TMP: 6-11 hours
    • SMX: 9-12 hours, prolonged in renal failure
  • Time to Peak, Serum: 1 to 4 hours
  • Excretion: Both are excreted in urine as metabolites and unchanged drug