Pharmacokinetics of metoprolol in healthy,elderly, non-smoking individuals after a single dose and two weeks of treatment

Summary The effect of long-term treatment on the absorption and dispsoition of metoprolol has been evaluated in 8 healthy, non-smoking, elderly individuals (mean age 74.5 years) and in a control group of 8 healthy, young individuals. Two trace doses of [³H]metoprolol were given i.v., first concomitantly with a single oral 50 mg dose of cold metoprolol, and second, with the morning dose after 2 weeks of treatment with 50 mg b.d. In the elderly, the mean AUC increased by about 45% (p<0.05) over the treatment period, while in the control group the mean AUC was 18% greater (p<0.05) on Day 14 than on Day 1. In the elderly, changes both in pre-systemic elimination and in total body clearance accounted for the elevation of the AUC, whereas reduced first-pass effect appeared to be the major cause of the increased steady-state plasma level in the control group. With the exception of the volume term, V , the pharmacokinetic parameters were not significantly different between the elderly and the young individuals. For this reason, almost identical steady-state plasma levels were attained in the two groups. The results suggest that age-related physiological changes may have some minor effects on the pharmacokinetics of metoprolol, and also that the changes do not lead to significantly altered plasma concentrations compared to those in young individuals.     

Duration of benzodiazepine clinical activity: Lack of direct relationship with plasma half-life

The anxiolytic activity and tolerance of two dosage schedules of prazepam, a long plasma half-life benzodiazepine, were compared under double-blind conditions in two groups of 10 inpatients each who met Research Diagnostic Criteria for Generalized Anxiety Disorder and presented chronic and severe symptomatology. Patients received prazepam 40 mg per day on one of two dosage schedules: 1) divided dosage (DD) - 10 mg in the morning and at noon and 20 mg in the evening; or 2) single dosage (SD) - 40 mg in the evening. The 3 weeks of therapy were preceded and followed by 1 week of wash-out for baseline and follow-up assessments, which were performed weekly with the Hamilton Anxiety Scale, Clinical Global Impression, rating of morning drowsiness and evening worsening of symptoms, and patient self-rating of anxiety by means of a visual analogue scale performed both in the morning and in the afternoon. The results showed a clear superiority of the DD over the SD schedule: better anxiolytic efficacy on the Hamilton Anxiety Scale (P<0.0005) and on both morning and afternoon visual analogue scales (P<0.01 andP<0.0002); less morning drowsiness (P<0.0001); and steadier anxiolytic effect during the daytime, as globally rated by the investigator (P<0.0001) or measured by morning-afternoon differences on the visual analogue scale (P<0.005). These results suggest that plasma pharmacokinetics alone may not be sufficient to predict the duration of benzodiazepine anxiolytic activity.     

Concentration andpH dependent steady-state volume of distribution of methotrexate estimated by a simple physiologically based method

The effects of plasma concentration and pH on the steady-state volume of distribution, V_ss,of methotrexate (MTX) were studied in five conditioned male beagle-mongrel dogs. Steady-state plasma MTX concentrations of approximately 1, 20, and 100g/ml were targeted for by i.v. bolus doses followed by i.v. infusions. An isotonic solution of sodium bicarbonate or ammonium chloride was simultaneously infused for the purpose of inducing plasma pH change, while the infusion of an isotonic solution of sodium chloride served as a control. Plasma and urine concentrations of MTX were quantitated by a sensitive high-performance liquid chromatographic method, and the V_ss of MTX was estimated by a recently reported physiologically based method of Chiou and Lam. Statistically significant (p<0.05) concentration and plasma pHdependent V_ss of MTX were observed. Concentration dependence of V_ss was noted in sodium chloride and ammonium chloride infused dogs, but not in bicarbonate treated dogs. There was an average 50.0 and 44.8% increase in V_ss at 1 g/ ml relative to the two higher concentrations (20 and 100 g/ ml) for dogs treated with ammonium and sodium chloride, respectively. However, V_ss of MTX at the targeted concentrations of 20 and 100 g/ml was relatively constant. Plasma pHdependence of V_ss was observed only at the plasma concentration of 1 g/ml, and on the average, ammonium chloride and sodium chloride treatments resulted in 50.0 and 31.3% higher V_ss,respectively, when compared with the bicarbonate treatment. These phenomena appear to be adequately explained by the reported tissue uptake kinetics of MTX.This research was supported in part by a grant from the National Cancer Institute, CA-29754.Abstracted from a dissertation submitted in 1984 by Chung Y. Lui to the Graduate College, University of Illinois at Chicago, in partial fulfillment of Doctor of Philosophy Degree requirements.     

The combined use of high-performance liquid chromatography and radioimmunoassay for the bioanalysis of nicomorphine and its metabolites

Methods have been developed for the determination of nicomorphine using reversed-phase HPLC with UV detection; for the simultaneous assay of morphine and mononicotinoylmorphine by a coupled normal-phase HPLC-radioimmunoassay method; and for conjugates of morphine and mononicotinoylmorphine by radioimmunoassay. The methods have been evaluated and applied to a pharmacokinetic study of nicomorphine administered intramuscularly.     

5-氟尿嘧啶白及微球家兔肾动脉栓塞后体内药代动力学研究

以常规5-氟尿嘧啶(5-Fu)注射液为对照品,研究了5-Fu白及微球家兔肾动脉栓塞后体内药代动力学过程.血药5-Fu浓度采用反相高效液相色谱法,所得血药浓度数据用3P87药代动力学程序处理.实验结果5-Fu白及微球体内过程符合二室模型,t1/2a(6.27±6.10)min,t1/2β(203.6±97.5)min,Cmax(4.8±1.9)μg/ml.t1/2a,t1/2β均比注射剂明显延长(P<0.01).表明微球剂型具有靶向制剂长效、高效、低毒的特点.     

国产与进口吲哚美辛缓释胶囊生物等效性评价

比较国产与进口吲哚美辛缓释胶囊在人体内的生物利用度和生物等效性.18名健康男性志愿者双周期随机交叉口服吲哚美辛缓释胶囊75 mg,用反相高效液相色谱法测定达稳态后的血药浓度.受试制剂与参比制剂的达峰时间(Tpeak)分别为(3.78±1. 00)h和(3.50±1.29)h;达峰浓度(Cmax)分别为(7.51±2.74)ug/ml和(8.05±2.58)ug/ml;药时曲线面积(AUC)分别为(66.41±30.12)和(63.90±26.50)ug@ml-1@h-1.多次给药达稳态条件下,国产的吲哚美辛缓释胶囊与进口制剂的相对生物利用度为(103.20±21.90)%.双单侧检验表明,国产与进口吲哚美辛缓释胶囊具有生物等效性.     

大剂量萘哌地尔在家犬体内的药物动力学

目的 :建立HPLC测定家犬血浆中萘哌地尔浓度的方法 ,研究大剂量萘哌地尔胶囊在家犬体内的药物动力学。方法 :健康家犬 5只 ,单剂量给予萘哌地尔胶囊 2 0 0mg后 ,在不同时间点从后肢静脉取血 ,血浆样品碱化后经乙醚提取 ,以乙腈 :磷酸盐缓冲液 (pH 6 .5 ) (6 0 :40 )为流动相 ,由ODSC18分析柱分离测定 ,紫外 2 30nm为检测波长 ,维拉帕米为内标。血药浓度数据用 3p97药物动力学程度处理。结果 :线性范围为 10～ 12 0 0ng·ml-1;方法回收率为98 83%～ 10 1 5 0 % ;日间RSD≤ 5 5 6 % ,日内RSD≤ 3 30 %。单剂量给予家犬萘哌地尔胶囊 2 0 0mg后 ,血药浓度随时间变化规律符合一室开放模型 ,T1/2Ke为 1 91～ 4 99h ,Tmax为 1 87～ 3 2 1h ,Cmax为 338 79～ 414 0 4ng·ml-1。结论 :本方法简便、回收率高、重现性好 ,用于大剂量萘哌地尔在动物体内的药物动力学研究 ,切实可行。     

HPLC法测定口服5—氨基水杨酸制剂后血浆和尿中的药物及其代谢物

目的建立测定血浆和尿样中5-氨基水杨酸(5-ASA)及代谢物乙酰-5-氨基水杨酸(Ac-5-ASA)浓度的HPLC方法,并进行5-ASA缓释片Pentasa的人体药动学研究.方法使用荧光检测器,以丙酰-4-氨基水杨酸为内标,用衍生化法使样品中的5-ASA丙酰化,甲醇沉淀蛋白后上清液直接进样.色谱柱为PhenomenexLunaTMC18,流动相为0.1mo1/L乙酸溶液乙腈三乙胺(460400.4,V/V/V)的混合液.测定6位健康志愿者口服1000magPentasa后血药浓度和尿药浓度.结果血浆中5-ASA及代谢物的线性范围为0.01～10μg/ml,尿样中为0.2～200μg/ml,血浆和尿中药物与代谢物的回收率在95.3%～106.2%之间,日内日间相对标准差均在052%～9.22%范围内.Pentasa口服后5-ASA和Ac-5-ASA的血药浓度在3～4h内达到峰值,分别为1.55和3.11μg/rl,AUC分别为6.90和26.32μg/(ml@h),60h内尿中排泄了口服剂量37.1%的药物.结论方法简便,灵敏度和准确度高,可用于5-ASA制剂的药物动力学研究.     

用双剂量实验数据分析药物的米氏消除参数的识别问题

本文分析了给药剂量对按一级过程吸收，米氏过程消除药物的血药浓度的峰值与达峰时间的影响。并据此讨论了利用较少的双剂量实验数据改善识别米氏参数的方法。