Drug Allergy

Adverse reactions to pharmaceutical and diagnostic products constitute a major hazard in the practice of medicine and are responsible for substantial morbidity and cost. Adverse drug reactions can be divided into predictable and unpredictable reactions. Predictable reactions including drug toxicity, drug interactions, and adverse effects are dose dependent, can be related to known pharmacologic actions of the drug and occur in patients without any unique susceptibility. In contrast, unpredictable reactions are dose independent, often not related to the pharmacologic actions of the drug and occur in susceptible patients. These include idiosyncratic reactions, allergic (hypersensitivity) reactions, and pseudoallergic reactions. Pseudoallergic reactions resemble allergic reactions but are distinguished by the fact that an immunologic mechanism is not involved. In this review, we will concentrate on drug allergy, its underlying immunological abnormalities, clinical manifestations, diagnosis and management.