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Lack of cross reactivity between sulfonamide antibiotics and nonantibiotic sulfonamides


I am seeing a 66 year-old gentleman with severe glaucoma who was referred to me by his ophthalmologist to determine if he is allergic to acetazolamide (Diamox). He has failed many other medications for treatment of his glaucoma and at this time declines surgical intervention. He is unsure if he ever took sulfa containing antibiotics but was advised at age 6 to avoid them for unknown reasons. Since Diamox is not a sulfonamide antibiotic, does he need to be skin tested to this medication or is the risk of cross reaction so low that this is not necessary?


From the Drug Allergy: An Updated Practice Parameter, October, 2010, see below, testing is not indicated.

"There are data suggesting that patients with a history of allergy to sulfonamide antibiotics are at slightly increased risk of reacting to nonantibiotic sulfonamides, although this does not appear to be due to immunologic cross reactivity but rather a nonspecific predisposition to react to drugs. Although all sulfonamides contain a NH2-SO2 moiety, sulfonamide antibiotics also contain an aromatic amine at the N4 position and a substituted ring at the N1 position, and these groups are believed to be essential for various types of allergic reactions to sulfonamide antibiotics."

We hope this helps.
Patricia McNally, MD, FAAAAI