May T W, Rambeck B, Nothbaum N
Biochemical Department, Gesellschaft für Epilepsieforschung, Bielefeld, FRG.
Eur Neurol. 1991;31(1):57-60. doi: 10.1159/000116647.
The interpretation of the total phenytoin (PT) concentration can be problematic if valproic acid (VPA) is given as a comedication, because VPA displaces PT from the protein binding sites and can increase the free fraction of PT. In order to estimate the free or unbound PT concentration (PTf) from the total PT concentration (PTt) and VPA concentration, a nomogram was constructed and evaluated. Data of 84 patients on combined therapy with PT and VPA were used in drawing up the regression equation (PTf = 0.0792.PTt + 0.000636.PTt.VPA) from which the nomogram was constructed. The predictions were checked using another 33 patients whose serum concentrations were determined in the morning and in addition several times during the day. The results show that using this method the PTf concentrations can be accurately estimated from the PTt and VPA concentrations.
如果丙戊酸（VPA）作为联合用药，总苯妥英（PT）浓度的解读可能会有问题，因为VPA会将PT从蛋白质结合位点上置换出来，并可能增加PT的游离分数。为了根据总PT浓度（PTt）和VPA浓度估算游离或未结合的PT浓度（PTf），构建并评估了一张列线图。绘制回归方程（PTf = 0.0792·PTt + 0.000636·PTt·VPA）时使用了84例接受PT和VPA联合治疗患者的数据，列线图即根据该方程构建。使用另外33例患者进行预测验证，这些患者的血清浓度在早晨测定，并且在一天中还多次测定。结果表明，使用该方法可以根据PTt和VPA浓度准确估算PTf浓度。
