Allergic and nonallergic drug reactions.

Allergic drug reactions may be difficult to distinguish from nonallergic reactions. In this article, we review a pragmatic approach to the management of adverse drug reactions on the basis of knowledge of the classification and patterns of these reactions. Algorithms for management of patients with a previous adverse drug reaction who require treatment for the same indication, and the approach to a patient who experiences a drug reaction while on multiple drugs, are presented.