He H, McKay G, Midha K K
College of Pharmacy, University of Saskatchewan, Saskatoon, Canada.
J Pharm Sci. 1993 Oct;82(10):1027-32.
A benztropine RIA based on polyclonal antisera raised in New Zealand white rabbits has been developed. The drug-protein conjugates employed had a variety of moles of benztropine hemisuccinate coupled per mole of protein (bovine serum albumin or bovine thyroglobulin). Six antisera were developed and the one with the highest titer was further evaluated for its cross reactivity to N-desmethylbenztropine (4%) and the antipsychotic agents fluphenazine, flupenthixol, chlorpromazine, and haloperidol (all < 1%). The selected antiserum demonstrated sufficient sensitivity to measure benztropine from 0.156 to 100 ng/mL plasma in a 200-microL plasma sample, with a mean CV of < 6%. The RIA was applied to the analysis of steady-state plasma samples obtained from patients undergoing treatment with benztropine and plasma samples obtained from human volunteers and dogs orally dosed with the drug. Both the human and dog plasma samples, when analyzed after hydrolysis with beta-glucuronidase/sulfatase, demonstrated increments in benztropine concentrations, suggesting the drug may be undergoing biotransformation to phase II metabolite(s). In addition, when benztropine was selectively extracted from the unhydrolyzed plasma samples, there was a significant decrease in drug level, which further suggested that the antiserum cross reacted with phase II metabolite(s). The shape of the plasma concentration versus time profile obtained from the dog studies suggested that the drug might also undergo enterohepatic recycling.
基于在新西兰白兔中产生的多克隆抗体制备了一种苯海索放射免疫分析方法。所使用的药物 - 蛋白质偶联物每摩尔蛋白质（牛血清白蛋白或牛甲状腺球蛋白）结合的苯海索半琥珀酸酯的摩尔数各不相同。制备了六种抗血清，对效价最高的抗血清进一步评估了其对N - 去甲基苯海索（4%）以及抗精神病药物氟奋乃静、三氟噻吨、氯丙嗪和氟哌啶醇（均<1%）的交叉反应性。所选抗血清表现出足够的灵敏度，可在200 μL血浆样本中检测0.156至100 ng/mL血浆中的苯海索，平均变异系数<6%。该放射免疫分析方法应用于分析接受苯海索治疗患者的稳态血浆样本以及口服该药物的人类志愿者和犬的血浆样本。在用β - 葡萄糖醛酸酶/硫酸酯酶水解后分析的人类和犬血浆样本中，苯海索浓度均有所增加，表明该药物可能正在生物转化为II相代谢物。此外，当从未水解的血浆样本中选择性提取苯海索时，药物水平显著降低，这进一步表明抗血清与II相代谢物发生了交叉反应。从犬类研究获得的血浆浓度与时间曲线的形状表明该药物可能还会进行肝肠循环。
