Risk Strom BL, Schinnar R, Apter AJ, et al: Absence of cross-reactivity between sulfonamide antibiotics and sulfonamide nonantibiotics. N Engl J Med 2003; 349(17):1628-35.

This retrospective cohort study used the General Practice Research Database in the United Kingdom to assess the risk of allergic reactions within 30 days after the receipt of a sulfonamide nonantibiotic (e.g. furosemide, glyburide, probenecid or hydrochlorothiazide). Overall, 4.8% of patients (969 of 20,225) had an apparent allergic reaction within 30 days after receiving the initial sulfonamide antibiotic. Of these, 96 (9.9%) had an allergic reaction after subsequently receiving a sulfonamide nonantibiotic. Of the 19,257 who had no allergic reaction after a sulfonamide antibiotic, 315 (1.6%) had an allergic reaction after a sulfonamide nonantibiotic (OR 2.8; 95% CI 2.1-3.7).

Among those with a prior hypersensitivity reaction after receiving a sulfonamide antibiotic, the risk of an allergic reaction after receiving a sulfonamide nonantibiotic was lower than the risk of allergy after receiving a penicillin (OR 0.7; 95% CI 0.5-0.9). Finally, the risk of allergy after sulfonamide nonantibiotic was lower in patients with a history of sulfonamide antibiotic allergy than it was among patients with penicillin allergy (OR 0.6; 95% CI 0.5-0.8). Although a history of allergy to sulfonamide antibiotics is a marker of increased risk on subsequent exposure to sulfonamide nonantibiotics, this risk appears to be due to a predisposition to allergic reactions rather than to cross-reactivity with sulfonamide based drugs. In fact, patients with a history of hypersensitivity to sulfonamide antibiotics are at even greater risk for subsequent reactions to penicillins, a biochemically distinct group, than to nonantibiotic sulfonamides.