Allergic reactions to phenytoin in a general hospital in Singapore.

Phenytoin is used for the treatment and prevention of fits. We investigated all patients reported to have phenytoin allergy in our hospital and found 42 confirmed cases. Sixty-nine percent were female and 83.3% were Chinese. The mean age of the patients was 46.5 years. The reactions reported were maculopapular rash (71.4%), Stevens-Johnson syndrome (14.3%), fever (4.8%), generalized exfoliative dermatitis (2.4%), toxic epidermal necrolysis (2.4%), vasculitis (2.4%) and agranulocytosis (2.4%). In conclusion, the majority of reported allergic reactions to phenytoin were cutaneous (92.9%) and one fifth of these were potentially life-threatening.