Table 2 Classification of allergic drug reactions: mechanisms, clinical manifestations, and timing of reactions [6,7,8,9].
From: Drug allergy
Immune reaction | Mechanism | Clinical manifestations | Timing of reaction |
|---|---|---|---|
Type I (IgE-mediated) | Drug-IgE complex binding to mast cells with release of histamine, inflammatory mediators | Anaphylaxisa, urticariaa, angioedemaa, bronchospasma | Minutes to hours after drug exposure |
Type II (cytotoxic) | Specific IgG or IgM antibodies directed at drug-hapten coated cells | Anemia, cytopenia, thrombocytopenia | Variable |
Type III (immune complex) | Tissue deposition of drug-antibody complexes with complement activation and inflammation | Serum sickness, vasculitis, fever, rash, arthralgia | 1–3 weeks after drug exposure |
Type IV (delayed, cell mediated) | MHC presentation of drug molecules to T cells with cytokine and inflammatory mediator release; may also be associated with activation and recruitment of eosinophils, monocytes, and neutrophils | Contact sensitivity, skin rashes, organ-tissue damage | 2–7 days after drug exposure |