Sulfadiazine warnings and precautions

# Warnings and Precautions

## Warnings
The sulfonamides should not be used for the treatment of group A betahemolytic streptococcal infections. In an established infection, they will not eradicate the streptococcus and, therefore, will not prevent sequelae such as rheumatic fever and glomerulonephritis.
Deaths associated with the administration of sulfonamides have been reported from hypersensitivity reactions, agranulocytosis, aplastic anemia and other blood dyscrasias.
The presence of such clinical signs as sore throat, fever, pallor, purpura or jaundice may be early indications of serious blood disorders.
The frequency of renal complications is considerably lower in patients receiving the more soluble sulfonamides.

## Precautions
General
Sulfonamides should be given with caution to patients with impaired renal or hepatic function and to those with severe allergy or bronchial asthma.
Hemolysis may occur in individuals deficient in glucose-6-phosphate dehydrogenase. This reaction is dose related.
Adequate fluid intake must be maintained in order to prevent crystalluria and stone formation.
Information for Patients
Patients should be instructed to drink an eight ounce glass of water with each dose of medication and at frequent intervals throughout the day. Caution patients to report promptly the onset of sore throat, fever, pallor, purpura or jaundice when taking this drug, since these may be early indications of serious blood disorders.
Laboratory Tests
Complete blood counts and urinalyses with careful microscopic examinations should be done frequently in patients receiving sulfonamides.
Drug Interactions
Administration of a sulfonamide may increase the effect of oral anticoagulants and methotrexate, probably by displacement of these drugs from binding sites on plasma albumin. Potentiation of the action of sulfonylurea hypoglycemic agents, thiazide diuretics and uricosuric agents may also be noted. This may also be due to displacement of the drugs from albumin or a pharmacodynamic mechanism may play a role. Conversely, agents such as indomethacin, probenecid and salicylates may displace sulfonamides from plasma albumin and increase the concentrations of free drug in plasma.
Carcinogenesis, Mutagenesis, Impairment of Fertility
The sulfonamides bear certain chemical similarities to some goitrogens. Rats appear to be especially susceptible to the goitrogenic effects of sulfonamides and long-term administration has produced thyroid malignancies in rats.
Pregnancy
Teratogenic Effects
Pregnancy Category C
The safe use of sulfonamides in pregnancy has not been established. The teratogenic potential of most sulfonamides has not been thoroughly investigated in either animals or humans. However, a significant increase in the incidence of cleft palate and other bony abnormalities in offspring has been observed when certain sulfonamides of the short, intermediate and long acting types were given to pregnant rats and mice in high oral doses (7 to 25 times the human therapeutic dose).
Nursing Mothers
Sulfadiazine is contraindicated for use in nursing mothers because the sulfonamides cross the placenta, are excreted in breast milk and may cause kernicterus.
Because of the potential for serious adverse reactions in nursing infants from sulfadiazine, a decision should be made whether to discontinue nursing or to discontinue the drug, taking into account the importance of the drug to the mother. See CONTRAINDICATIONS.
Pediatric Use
Sulfadiazine is contraindicated in infants less than 2 months of age (except as adjunctive therapy with pyrimethamine in the treatment of congenital toxoplasmosis). See CONTRAINDICATIONSand DOSAGE AND ADMINISTRATION.