sulfadiazine: clinical use

Prescribing considerations

• Confirm that the suspected organism and clinical context support sulfonamide use; seek microbiology or infection-specialist advice for uncommon infections.
• Toxoplasmosis use is specialist-led and normally involves combination therapy with folinic-acid support.
• Ensure adequate hydration where clinically appropriate to reduce crystalluria risk.
• Actively distinguish sulfadiazine from sulfasalazine during prescribing, dispensing and medicines reconciliation.
• Use additional caution with renal or hepatic impairment, older age, folate deficiency, G6PD deficiency, lupus, HIV/AIDS, asthma or previous allergy.

Contraindications and cautions

• Hypersensitivity to sulfadiazine or another sulfonamide
• Severe renal or hepatic failure
• Acute porphyria
• Jaundice or an existing blood disorder
• Neonatal use
• Concurrent clozapine
• Previous sulfadiazine-associated Stevens–Johnson syndrome or toxic epidermal necrolysis

Monitoring

• Full blood count during prolonged treatment and promptly if infection, oral ulceration, bruising or bleeding develops.
• Renal function and urine assessment when treatment is prolonged, renal function is impaired or crystalluria is suspected.
• Assess skin and mucosal symptoms closely, particularly early in treatment.
• Consider interaction-specific monitoring, including anticoagulation, glucose, phenytoin, methotrexate or ciclosporin effects as applicable.

Clinical pharmacology

A competitive PABA antagonist that inhibits microbial folate synthesis. It is rapidly absorbed orally, partly protein-bound and eliminated mainly through urine.

Formulation and product differences

• The selected product is a plain white, biconvex oral tablet marked “CP” on one face.
• Its listed excipients include starches, microcrystalline cellulose, sodium starch glycolate, talc and magnesium stearate.

Tablet

Route: Oral

Strengths: 500 mg