Revised Winter-Tozer equation for normalized phenytoin concentrations in trauma and elderly patients with hypoalbuminemia.

ObjectiveTo develop a revised equation reflecting the current practice of measuring unbound phenytoin at room temperature, and to evaluate the revised Winter–Tozer method of predicting normalized total phenytoin concentrations in two groups of patients with hypoalbuminemia — elderly nursing home patients and critically ill head trauma patients.DesignAlbumin, unbound phenytoin, and total phenytoin concentrations were obtained from two sources: prospectively from a group of elderly nursing home patients and by a retrospective chart review of trauma patients enrolled in a previous double-blind, placebo-controlled study.SettingCommunity nursing homes; a university-affiliated urban teaching hospital.ParticipantsElderly nursing home patients (n = 46) taking chronic phenytoin therapy and patients enrolled in a double-blind, placebo-controlled study (n = 58) evaluating the use of phenytoin to prevent posttraumatic seizures.Main Outcome MeasuresPrediction error analysis was performed by using the methods proposed ...