What is known and Objective
Prescribing sulfonamide-containing medications for patients with sulfonamide allergy continues to complicate medical decisions. We examined the cautionary recommendations in the approved drug monographs and primary literature, and formulated an evidence-based grading of cautionary recommendations for sulfonamide allergy and cross-reactivity among sulfonamide-containing medications.
Drug monographs were collected from six countries and three drug compendia. Two reviewers independently extracted the data from the contraindication, warning and/or precaution sections of drug monographs. Evidence for cross-reactivity was examined in the primary literature and compared with drug monograph recommendations. Consequently, medications were categorized based on the strength of recommendation and level of evidence by consensus.
Results and Discussion
We identified wide variability in cautionary recommendations ranging from no warning or precaution to contraindication among the sources reviewed. The recommendations were located mainly in the contraindication section of monographs for France (65·2%), United Kingdom (51·9%), Italy (50·0%), South Korea (43·5%), United States (38·2%) and Canada (37·0%), whereas in drug compendia, the recommendations were found in the precaution section for Martindale (51·4%) and Micromedex-Drugdex (33·3%), and contraindication and precaution section for the American Hospital Formulary Service Drug Information 2010 (30·8%). Evidence from the primary literature varied with recommendation included in drug monographs. Evidence-based categorization was carried out for 16 medications. Two sulfonamide-moiety-containing drugs were considered safe, six non-sulfonylarylamines required precaution, and eight medications from all three sulfonamide chemical classes were considered mostly unsafe.
What is new and Conclusion
There are significant discrepancies in cautionary recommendations included in drug-labels and drug compendia. Statements concerning cross-reactive hypersensitivity with other sulfonamides generally suggest theoretical possibilities. The consensus evidence-based grading instrument developed may be useful for deriving cautionary recommendations for sulfonamide-allergic patients.