Section 15 · Monograph
Sulfadiazine
Reviewed Nov 2026FDA label
SulfadiazineSulfonamide antibiotic
- Forms
- Tab: 500mg
- Dose
- Cerebral toxoplasmosis: 1,000mg (under 60kg) or 1,500mg (60kg or more) every 6 hours with pyrimethamine and leucovorin
- MOA
- Inhibits dihydropteroate synthase
Indications
- Toxoplasmosis (adjunct with pyrimethamine), chancroid, nocardiosis and other sulfonamide-susceptible infectionsFDA-labeled
Mechanism of Action
- Competitive inhibitor of bacterial and protozoal dihydropteroate synthase; synergistic with DHFR inhibitors
Full Dosing
Adult / usual
- Cerebral toxoplasmosis: 1,000mg (under 60kg) or 1,500mg (60kg or more) PO every 6 hours with pyrimethamine and leucovorin
- Maintain urine output of at least 2-3 liters/day (hydration) to reduce crystalluria
Renal
- Reduce dose in renal impairment
Contraindications
- Hypersensitivity to sulfonamides
- Infants under 2 months of age (except in congenital toxoplasmosis)
- Porphyria (relative); pregnancy near term
Drug Interactions
- Warfarin, phenytoin and methotrexate levels may increase
- Other myelosuppressive and nephrotoxic drugs
Adverse Effects
- Crystalluria, nephrolithiasis and acute kidney injury
- Rash, Stevens-Johnson syndrome
- Cytopenias, hepatitis, fever
- Hypoglycemia
Monitoring Parameters
- Renal function and urinalysis
- CBC
- Hydration and liver enzymes
Pregnancy & Lactation
- Avoid near term (kernicterus risk) except when treating toxoplasmosis
- Avoid in nursing infants with G6PD deficiency or jaundice