A comparative study of laboratory parameters in head-injured patients receiving either phenytoin or placebo for 24 months

The effects of chronic phenytoin therapy on serum calcium, phosphorus, folate, and various hematological indices were assessed. One hundred and fifty-one patients, ages 18 months to 81 years, received phenytoin in a previously-conducted, double-blind, placebo-controlled study. Of the patients receiving phenytoin, initially 127 were evaluable while for control patients receiving placebo, 116 were evaluable. All patients had various laboratory parameters monitored at one day post-loading dose, one week, 1,3,6,9,12,15,18,21, and 24 months. Laboratory values examined were serum calcium, phosphorus, folate, white blood cell count with differential, hemoglobin, hematocrit, and red blood cell and platelet counts. A statistical analysis using the t-test method was employed to evaluate data. Data are reported as mean values +/- standard deviation. Patients suffering early hypersensitivity, manifested by a morbilliform skin rash, were removed from the drug by day 30 and were not included in the chronic therapy review. Results indicate that the various laboratory values examined were not significantly affected by phenytoin administration in the patient population. Therefore, chronic phenytoin therapy following the initial hypersensitivity period does not cause abnormal laboratory values as followed in this study.