Drug Allergy
An immune-mediated adverse reaction to a medication, distinct from predictable pharmacological side effects. Drug allergies involve the immune system recognising the drug as foreign and mounting a response. True allergic reactions to peptide drugs are uncommon but can include urticaria, angioedema, and anaphylaxis.
Technical Context
True drug allergy involves adaptive immune system activation against the drug or its metabolites. Evaluation includes: clinical history (timing, symptoms, reproducibility), skin testing (immediate — prick/intradermal testing for IgE; delayed — patch testing for T-cell-mediated), in vitro testing (drug-specific IgE, basophil activation test), and graded challenge/desensitisation (administering incremental doses under medical supervision). For peptide drugs, true allergic reactions are uncommon compared to non-immune adverse effects (pharmacological side effects, injection site reactions). When allergy is suspected, the offending peptide should be discontinued and alternative agents from the same class (which may have different immunogenic epitopes) or different classes should be considered. Desensitisation protocols exist for peptide drugs that are essential and lack alternatives.