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Tuesday, August 11, 2015

Report from the National Institute of Allergy and Infectious Disease Workshop on Drug Allergy

Allergic reaction to drugs is a serious and often underserved public health concern. In 2013, the National Institute of Allergy and Infectious Diseases (NIAID) Division of Allergy, Immunology and Transplantation convened a workshop on the issue. Representatives from several NIH institutes and from the FDA joined experts in drug allergy for a day-long discussion. Wheatley et al present a summary of the topics and recommendations (J Allergy Clin Immunol 2015; 136(2): 262-271).

The authors define “drug allergy” as any adverse drug reaction (ADR) that has a proven immunologic mechanism, including but not limited to IgE-mediated disease. There are currently no systematic epidemiologic studies of drug allergy. Most of the epidemiologic data on adverse drug reactions (ADRs) at this point relies on clinical diagnosis. With few specific diagnostic tests, physician-based assessment remains the gold standard for phenotyping the reactions.

ADRs are categorized as type A or type B. Type A reactions result from known pharmacologic/toxic effects of the drug often related to dosage. Mechanisms other than pharmacologic toxicity mediate type B reactions, which constitute approximately 20% of ADRs. The majority of type B reactions have an immunological basis. In particular, IgE-mediated reactions, whether immediate or delayed, often occur with a single encounter with the allergen. The mechanisms underlying both immediate-onset and delayed-onset reactions remain elusive. In no small part, this is due to a lack of appropriate reagents and reliable tests to detect drug-specific IgE antibodies and an absence of model systems.

While drug desensitization has a risk of inducing an allergic reaction, it is the only currently available approach that appears to provide clinical benefit. There is a need for valid, rapid, and inexpensive screening tests. While immunologically mediated ADRs are common, there will be few patients with the same reaction to the same drug in the same clinical context in any one institution. The authors call for multi-center clinical networks and communication between investigators, funding and regulatory agencies, and the pharmaceutical industry as the field grows.

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