Approach to managing patients with sulfa allergy: use of antibiotic and nonantibiotic sulfonamides.

OBJECTIVE To present an approach to use of sulfonamide-based (sulfa) medications for patients with sulfa allergy and to explore whether sulfa medications are contraindicated for patients who require them but are allergic to them.

SOURCES OF INFORMATION A search of current pharmacology textbooks and of MEDLINE from 1966 to the present using the MeSH key words "sulfonamide" and "drug sensitivity" revealed review articles, case reports, one observational study (level II evidence), and reports of consensus opinion (level III evidence).

MAIN MESSAGE Cross-reactivity between sulfa antibiotics and nonantibiotics is rare, but on occasion it can affect the pharmacologic and clinical management of patients with sulfa allergy.

CONCLUSION How a physician approaches using sulfa medications for patients with sulfa allergy depends on the certainty and severity of the initial allergy, on whether alternatives are available, and on whether the contemplated agent belongs to the same category of sulfa medications (ie, antibiotic or nonantibiotic) as the initial offending agent.