DeMonaco H J, Lawless L M
Arch Neurol. 1983 Aug;40(8):481-3. doi: 10.1001/archneur.1983.04210070021007.
The variability of protein binding of phenytoin in epileptic patients was evaluated using a rapid ultrafiltration system. Thirty-one pairs of total and free (unbound) phenytoin plasma concentrations were reviewed. Filtered plasma for free phenytoin determination was obtained using an ultrafiltration membrane system. All samples were analyzed by an enzyme-multiplied immunoassay technique. A good correlation was obtained for total phenytoin concentration v free phenytoin concentration. Comparison of obtained and predicted free phenytoin values differed significantly. Of nine patients demonstrating toxic effects, six had total phenytoin concentrations within the accepted therapeutic range with free concentrations above the therapeutic range. The results of this study indicate a wide variation of phenytoin protein binding in chronic epileptic patients, implying that total phenytoin concentration must be interpreted cautiously, and use of free phenytoin concentration appears to be a more appropriate guide to therapy. The availability of a rapid method of ultrafiltration makes free phenytoin plasma levels readily available to the clinician.
使用快速超滤系统评估癫痫患者苯妥英蛋白结合的变异性。回顾了31对苯妥英总血浆浓度和游离（未结合）血浆浓度。使用超滤膜系统获取用于测定游离苯妥英的过滤血浆。所有样本均采用酶放大免疫分析技术进行分析。苯妥英总浓度与游离苯妥英浓度之间具有良好的相关性。获得的游离苯妥英值与预测值相比存在显著差异。在9名出现毒性作用的患者中，6名患者的苯妥英总浓度在公认的治疗范围内，但游离浓度高于治疗范围。本研究结果表明，慢性癫痫患者中苯妥英蛋白结合存在广泛差异，这意味着必须谨慎解释苯妥英总浓度，而使用游离苯妥英浓度似乎是更合适的治疗指导。快速超滤方法的可用性使临床医生能够轻松获得游离苯妥英血浆水平。
