Classifications: sulfonamide antibiotic;
Therapeutic: antibiotic, sulfonamide

Prototype: Sulfisoxazole
Pregnancy Category: C


500 mg tablets


Short-acting sulfonamide, slightly less soluble than sulfisoxazole. Exerts bacteriostatic effect by interfering with bacterial utilization of PABA, thereby inhibiting folic acid biosynthesis required for bacterial growth.

Therapeutic Effect

Effective against a wide range of gram-positive and gram-negative microorganisms.


Used in combination with pyrimethamine for treatment of cerebral toxoplasmosis and chloroquine-resistant malaria.


Hypersensitivity to sulfonamides or to any ingredients in the formulation; porphyria; pregnancy (category C); at term pregnancy; lactation.

Cautious Use

Application of lotion to denuded or debrided skin; dehydration; hepatic disease; impaired renal function.

Route & Dosage

Mild to Moderate Infections
Adult: PO Loading Dose 2–4 g loading dose PO Maintenance Dose 2–4 g/d in 4–6 divided doses
Child: PO Loading Dose >2 mo, 75 mg/kg  PO Maintenance Dose 150 mg/kg/d in 4–6 divided doses (max: 6 g/d)

Rheumatic Fever Prophylaxis
Adult: PO <30 kg, 500 mg/d; >30 kg, 1 g/d

Adult: PO 2–8 g/d divided q6h
Child (>2 mo): PO 100–200 mg/kg/d divided q6h
Neonate: PO 50 mg/kg q12h x 12 mo


  • Maintain sufficient fluid intake to produce urinary output of at least 1500 mL/24 h for children between 3000 and 4000 mL/24 h for adults. Concomitant administration of urinary alkalinizer may be prescribed to reduce possibility of crystalluria and stone formation.
  • Store in tight, light-resistant containers.

Adverse Effects (≥1%)

CNS: Headache, peripheral neuritis, peripheral neuropathy, tinnitus, hearing loss, vertigo, insomnia, drowsiness, mental depression, acute psychosis, ataxia, convulsions, kernicterus (newborns). GI: Nausea, vomiting, diarrhea, abdominal pains, hepatitis, jaundice, pancreatitis, stomatitis. Hematologic: Acute hemolytic anemia (especially in patients with G6PD deficiency), aplastic anemia, methemoglobinemia, agranulocytosis, thrombocytopenia, leukopenia, eosinophilia, hypoprothrombinemia. Body as a Whole: Headache, fever, chills, arthralgia, malaise, allergic myocarditis, serum sickness, anaphylactoid reactions, lymphadenopathy, local reaction following IM injection, fixed drug eruptions, diuresis, overgrowth of nonsusceptible organisms, LE phenomenon. Skin: Pruritus, urticaria, rash, erythema multiforme including Stevens-Johnson syndrome, exfoliative dermatitis, alopecia, photosensitivity, vascular lesions. Urogenital: Crystalluria, hematuria, proteinuria, anuria, toxic nephrosis, reduction in sperm count. Metabolic: Goiter, hypoglycemia. Special Senses: Conjunctivitis, conjunctival or scleral infection, retardation of corneal healing (ophthalmic ointment).


Drug: paba-containing local anesthetics may antagonize sulfa's effects; oral anticoagulants potentiate hypoprothrombinemia; may potentiate sulfonylurea-induced hypoglycemia. May decrease concentrations of cyclosporine; may increase levels of phenytoin.


Absorption: Readily absorbed from GI tract. Peak: 3–6 h. Distribution: Distributed to most tissues, including CSF; crosses placenta. Metabolism: In liver. Elimination: In urine.

Nursing Implications

Assessment & Drug Effects

  • Lab tests: Baseline and periodic urine C&S to determine drug effectiveness; with long-term therapy, CBC, Hct, and Hgb.
  • Monitor hydration status.

Patient & Family Education

  • Take drug exactly as prescribed. Do not alter schedule or dose; take total amount prescribed unless physician changes the regimen.
  • Drink fluids liberally unless otherwise directed.
  • Report early signs of blood dyscrasias (sore throat, pallor, fever) promptly to the physician.

Common adverse effects in italic, life-threatening effects underlined; generic names in bold; classifications in SMALL CAPS; Canadian drug name; Prototype drug

© 2006-2023 Last Updated On: 02/01/2023 (0)
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