Cross-reactivity between sulfonamides
Antibiotic sulfonamides (eg sulfamethoxazole, sulfadiazine) and dapsone (a sulfone antibiotic closely resembling sulfonamide antibiotics) are often avoided in patients who are allergic to nonantibiotic sulfonamides (eg furosemide). However, this is usually not necessary because there is no cross-reactivity between antibiotic and nonantibiotic sulfonamides, with the exception of sulfasalazine (which is structurally similar to sulfonamide antibiotics). Avoid sulfasalazine in patients with antibiotic sulfonamide allergy, and vice versa.
Sulfasalazine is the only nonantibiotic sulfonamide with cross-reactivity to antibiotic sulfonamides.
Antibiotic sulfonamides (eg sulfamethoxazole) can be used in patients who are allergic to nonantibiotic sulfonamides (except sulfasalazine).
Evidence shows that the rate of immune-mediated cross-reactivity between antibiotic sulfonamides (including dapsone) is lower than previously thought. An antibiotic sulfonamide can be used in a patient with a history of nonsevere allergy to a different antibiotic sulfonamideKhan, 2019. In patients with a severe allergy to an antibiotic sulfonamide (eg anaphylaxis or a severe cutaneous adverse reaction such as drug rash with eosinophilia and systemic symptoms [DRESS] or Stevens–Johnson syndrome / toxic epidermal necrolysis [SJS/TEN]), do not use any other antibiotic sulfonamide.
For more information about allergy to sulfonamides, including a patient information sheet, see the Australasian Society of Clinical Immunology and Allergy (ASCIA) website.