Nandedkar A K, Williamson R, Kutt H, Fairclough G F
Ther Drug Monit. 1980;2(4):427-30.
Monitoring the blood levels of antiepileptic drugs (AED) has proven to be of value in the clinical management of epileptic patients. We have compared the plasma concentrations of AED determined by enzyme multiplied immunoassays (EMIT) and gas-liquid chromatography (GLC) assays and identified a group of patients (n = 22) in whom the EMIT values for phenytoin were up to three times higher than those obtained by GLC. All these patients were oliguric with various degrees of azotemia, most of them undergoing weekly hemodialysis. The ratio of EMIT over GLC was 2.0 in 14 patients, 2.5 in 5 patients, and near 3.0 in 3 patients. These ratios remained relatively constant during repeated determinations over several months. The magnitude of difference between EMIT and GLC values (microgram/ml) was not related to the degree of azotemia. The discrepancy remained unchanged when various modifications of EMIT and GLC techniques were used. When phenytoin was added in vitro to plasma from nonepileptic oliguric azotemic patients, the measured phenytoin values were close to and not higher than the target values by either methodology. We feel that, when monitoring phenytoin blood levels in epileptic patients with renal insufficiency, one should be aware of a discrepancy between phenytoin values assayed by GLC and EMIT.
监测抗癫痫药物（AED）的血药浓度已被证明在癫痫患者的临床管理中具有重要价值。我们比较了采用酶放大免疫分析法（EMIT）和气液色谱法（GLC）测定的AED血浆浓度，并确定了一组患者（n = 22），这些患者苯妥英的EMIT值比GLC法测定值高出两倍。所有这些患者均少尿并伴有不同程度的氮质血症，其中大多数人每周进行血液透析。14名患者的EMIT与GLC比值为2.0，5名患者为2.5，3名患者接近3.0。在数月的重复测定过程中，这些比值保持相对稳定。EMIT和GLC值（微克/毫升）之间的差异幅度与氮质血症程度无关。当对EMIT和GLC技术进行各种改进时，这种差异仍然不变。当将苯妥英体外添加到非癫痫性少尿氮质血症患者的血浆中时，两种方法测得的苯妥英值均接近且不高于目标值。我们认为，在监测肾功能不全的癫痫患者苯妥英血药浓度时，应注意GLC法和EMIT法测定的苯妥英值之间存在差异。
