Trimethoprim-sulfamethoxazole

C. diff Risk

Low

Oral Bioavailability

NA

Approximate Cost

IV$100/d PO$1/d

Dosing

UTI prophylaxis: 2 mg TMP/kg/DAY given as a single daily dose.

PJP prophylaxis in immunocompromised patients: 5 mg TMP/kg/DAY or 150 mg/m2/DAY PO given as a single daily dose or divided q12h for 2-7 days per week

Meningitis/PJP infection: IV: 15-20 mg TMP/kg/DAY divided q6-12h

Note dosing is expressed in mg of trimethoprim component.
Usual dose: Infants ≥2 months, Chidren, and Adolescents: Oral, IV: 6 to 12 mg TMP/kg/DAY divided q12h; Maximum: 320 mg TMP/DAY.

Use caution in infants <2 months old due to risk of kernicterus. No dosing references available.

Renally cleared, requires dosage adjustment with changes in renal function. Consult a pharmacist for renal dosing.

General Information

Common Usage

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

Drug Monitoring

Follow creatinine and electrolytes in patients at increased risk renal failure, hyperkalemia, CBC for cytopenias.

Adverse Effects

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

Major Interactions

ACEi - increased serum potassium level

Methotrexate- marrow suppression

Increases phenytoin <br>Increases INR with warfarin

Additional Information

Pediatric strength tablets 100mg SMX/ 20 mg TMP. Regular strength tablets 400mg SMX/ 80 mg TMP. Double strength tablets 800 mg SMX/ 160mg TMP

Pharmacology

Antimicrobial class: Sulfonamide - Antifolate

Average serum half life: TMP (prolonged in renal failure) Newborns: ~19 hours; range: 11-27 hours
infants 2 months to 1 year: ~4.6 hours; range: 3-6 hours.
Children 1-10 years: 3.7-5.5 hours.
Children and Adolescents >10 years: 8.19 hours
Adults: 6-11 hours
SMX: 9-12 hours, prolonged in renal failure (Adult data)

Route of Elimination: Both excreted in urine as metabolites and unchanged drug