- Tablets 500 mg
Exerts bacteriostatic action by competing with PABA, an essential component in folic acid synthesis, therefore preventing synthesis of folic acid needed by bacteria for growth.
Absorbed rapidly from the GI tract. A peak level of 6.04 mg per 100 mL is reached 4 h after a single 2 g oral dose (4.65 mg per 100 mL is free or active drug).
Protein binding is 38% to 48%. Diffuses into CSF, reaching concentrations of 32% to 65% of blood levels.
At least 1 acetylated form.
Excreted primarily in the urine, reaching concentrations that are 10 to 25 times higher then serum levels. About 10% of a single oral dose is excreted in the first 6 h, 50% within 24 h, and 60% to 85% in 48 to 72 h. 15% to 40% is excreted in the acetyl form.
Indications and Usage
Treatment of chancroid, trachoma, inclusion conjunctivitis, nocardiosis, UTI, toxoplasmosis encephalitis, malaria, meningococcal meningitis, acute otitis media; prophylaxis against meningococcal meningitis and recurrences of rheumatic fevers; with streptomycin as adjunctive therapy for Haemophilus influenza meningitis.
Hypersensitivity to sulfonamides; infants less than 2 mo of age (except as adjunctive therapy with pyrimethamine in treating congenital toxoplasmosis); pregnancy at term; nursing period.
Dosage and AdministrationAdults
PO 2 to 4 g, divided into 3 to 6 doses, every 24 h.Children older than 2 mo of age
PO Initially, one-half the 24-h dose.Maintenance
150 mg/kg or 4 g/m 2 , divided into 4 to 6 doses, every 24 h.Rheumatic Fever Prophylaxis
Under 30 kg give 500 mg every 24 h; over 30 kg give 1 g every 24 h.
Store tablets at ambient room temperature (59° to 86°F).
Drug InteractionsAnticoagulants, hydantoins (eg, phenytoin), methotrexate, sulfonylureas, thiazide diuretics, uricosuric agents
Effects of these agents may be enhanced by sulfadiazine.Indomethacin, probenecid, salicylates
May increase free sulfadiazine plasma levels, increasing the pharmacologic and adverse effects.
Laboratory Test Interactions
None well documented.
Headache; peripheral neuritis; mental depression; convulsions; ataxia; hallucinations; vertigo; insomnia.
Nausea; emesis; abdominal pain; diarrhea; anorexia; pancreatitis; stomatitis.
Crystalluria; stone formation; toxic nephrosis with oliguria and anuria; periarteritis nodosa; lupus erythematosus phenomenon.
Agranulocytosis; aplastic anemia; thrombocytopenia; leukopenia; hemolytic anemia; purpura; hypoprothrombinemia; methemoglobinemia.
Allergic reactions including erythema multiforme (Stevens-Johnson syndrome), generalized skin eruptions, toxic epidermal necrolysis, urticaria, serum sickness, pruritus, exfoliative dermatitis, anaphylactoid reactions, periorbital edema, conjunctival and scleral injection, photosensitization, arthralgia, allergic myocarditis, drug fever, and chills.
Category C .
Excreted in breast milk; use is contraindicated.
Contraindicated in children under 2 mo of age (except as adjunctive therapy with pyrimethamine in treating toxoplasmosis).
Special Risk Patients
Use with caution in patients with renal or hepatic function impairment and those with severe allergy or bronchial asthma.
May occur if adequate fluid intake is not maintained.
Group A beta-hemolytic streptococcal infections
Do not use drug for this infection.
May occur in G-6-PD-deficient individuals.
Severe reactions, including deaths, have been associated with hypersensitivity reactions, agranulocytosis, aplastic anemia, other blood dyscrasias, and renal and hepatic damage.
Has chemical similarities to some goitrogens, diuretics (eg, acetazolamide, thiazides), and oral hypoglycemic agents. Goiter production, diuresis, and hypoglycemia have occurred rarely in patients receiving sulfonamides; cross-sensitivity may exist.
- Review dosing schedule and prescribed length of therapy with patient.
- Advise patient to take each dose with a full (8 oz) glass of water without regard to meals. Advise patient to take with food if stomach upset occurs.
- Remind patient to complete entire course of therapy, even if symptoms of infection have disappeared.
- Advise patient to contact health care provider if infection does not seem to be improving or is worsening.
- Advise patient to drink fluids liberally (eg, eight 8-oz glasses of water daily) while taking this medication.
- Advise patient to discontinue therapy and contact health care provider immediately if any of the following symptoms occur: rash, hives, itching, sore throat, unexplained fever, pallor, purple spots under the skin, blood in urine, yellowing of the skin or eyes.
- Warn patient that diarrhea containing blood or pus may be a sign of a serious disorder and to seek medical care if noted and not treat at home.
- Advise patient to avoid unnecessary exposure to sunlight or tanning lamps and to use sunscreen and wear protective clothing to avoid photosensitivity reactions.
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