| Type of Reaction | Pathogenesis | Examples of Causative Drug | Clinical Patterns |
|---|---|---|---|
Type I | IgE-mediated; immediate-type immunologic reactions | Penicillin, other antibiotics | Urticaria/angioedema of skin/mucosa, edema of other organs, and anaphylactic shock |
Type II | Drug + cytotoxic antibodies cause lysis of cells such as platelets or leukocytes | Penicillin, sulfonamides, quinidine, isoniazid | Petechiae due to thrombocytopenic purpura, drug-induced pemphigus |
Type III | IgG or IgM antibodies formed to drug; immune complexes deposited in small vessels activate complement and recruitment of granulocytes | Immunoglobulins, antibiotics, rituximab, infliximab | Vasculitis, urticaria, serum sickness |
Type IV | Cell-mediated immune reaction; sensitized lymphocytes react with drug, liberating cytokines, which trigger cutaneous inflammatory responseb | Sulfamethoxazole, anticonvulsants, allopurinol | Morbilliform exanthematous reactions, fixed drug eruption, lichenoid eruptions, Stevens-Johnson syndrome, toxic epidermal necrolysis |
a After the Gell and Coombs classification of immune reactions.
b For contact sensitivity see Section 2.