Phenytoin hypersensitivity: 38 cases.

To determine the frequency and severity of hypersensitivity reactions to phenytoin, we reviewed 38 cases of proven reactions. Patients were included only if no other drugs, including other anticonvulsants, were in use at the time of the reaction. Rashes were most frequent, followed by fever, lymphadenopathy, eosinophilia, abnormal liver function tests, blood dyscrasias, serum sickness, renal failure, and polymyositis. The pseudolymphoma syndrome, (fever, rash, and lymphadenopathy) occurred in nine patients. Thirty-five of the 38 reactions occurred within 2 months of the start of therapy. Phenytoin sensitivity accounted for 467 inpatient days during the 14 years of study. Early recognition of phenytoin reactions, prompt drug withdrawal, and appropriate therapeutic measures were necessary to prevent serious morbidity from phenytoin hypersensitivity.