Trimethoprim-Sulfamethoxazole

C. diff Risk

Low

Oral Bioavailability

Excellent

Approximate Cost

IV:$$$
PO:$

Dosing

Adult

PO: 1-2 DS tabs PO BID

IV: 10-20mg/kg/day of TMP IV in 3-4 divided doses

General Information

Common Usage

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

Drug Monitoring

Laboratory

  • With high dose: consider baseline and periodic measurement of Cr (dose adjustment and nephrotoxicity assessment)

  • CBC

  • K

  • LFTs

Clinical

  • Hypersensitivity

  • GI effects

Adverse Effects

  • Nausea

  • Vomiting

  • Hypersensitivity reactions, bone marrow suppression

  • Hyperkalemia

Major Interactions

  •  ACEi - increased serum potassium level

  •  Increases amantadine levels

  •  Decreases cyclosporine

  •  Methotrexate - marrow suppression

  •  Increases phenytoin

  •  Increases rifampin

  •  Increases INR with warfarin

Pharmacology

Antimicrobial class: Sulfonamide - Antifolate

Pregnancy category: C

Average serum half life: 10 hours

Biliary penetration: Moderate

CSF penetration: Therapeutic

Lung penetration: Therapeutic

Urine penetration: Therapeutic