Pharmacokinetics of hexobarbital in man after intravenous infusion

The plasma levels of hexobarbital in humans were determined during and after a 30-min or 60-min zero-order intravenous infusion. Hexobarbital kinetics could be described by conceiving the body to exhibit two compartments. The plasma concentrations were fitted to the postinfusion equation and the parameters intrinsic to the two- compartment open model were estimated. The elimination half-life varied considerably among the 14 individuals (160–441 min), which could mainly be explained by the greatly varying metabolic clearance of the compound (123–360 ml /min). The apparent volume of distribution per kilogram of body weight was relatively constant (1.10±0.12 liters/kg).This work was supported in part by a grant from the Netherlands Foundation for Medical Research FUNGO.     

Pharmacokinetics of propylthiouracil in man after intravenous infusion

The kinetics of propylthiouracil in man was evaluated in four subjects after intravenous infusion at different infusion rates. Significant correlation among the rate of infusion, steadystate plasma levels, and AUC sustained the assumption of a doseindependent kinetics. The total body clearance and the elimination halflife evaluated after cessation of the infusion were in close agreement with values obtained in a previous study after intravenous bolus injection. The total volume of distribution was larger after infusion than found in the singleinjection studies. Data obtained from the infusions made it possible to evaluate the a phase indirectly.This work was supported by Grant 512-4121 from the Danish Medical Research Council, Copenhagen.     

Pharmacokinetics of bretylium in man after intravenous administration

The pharmacokinetic profile of bretylium was studied in four normal male volunteers using a new sensitive EC-GC procedure for its quantitation in biological fluids. The plasma concentrations and urinary excretion rates following the constant i.v. infusion of a single 4mg/kg dose of bretylium tosylate declined biexponentially and the data were fitted to a two-compartment model with a renal and a nonrenal route of elimination. The drug had a mean half-life (t_1/2)of 7.8 hr and apparent volume of distribution (V_d,)of 8.18 liters/kg. The renal clearance, which was 6 times that of the glomerular filtration rate, accounted for almost 84% of the total body clearance and correlated linearly with the subjects' creatinine clearance. The observed side effects of bretylium were mild and similar to those of other adrenergic blocking agents.This work was supported in part by a grant from Arnar-Stone Laboratories, Inc., McGaw Park, Illinois.     

Pharmacokinetics of intravenous fluticasone propionate in healthy subjects

1 Fluticasone propionate (FP) is a potent glucocorticoid used in the treatment of asthma. Prior to reporting the pharmacokinetics following the inhaled and oral routes, the pharmacokinetics need to be established following intravenous dosing. The present study determines the intravenous pharmacokinetics of FP, using non-compartmental analysis, in healthy male subjects over the 250 to 1000μg dose range.
2 The pharmacokinetics of FP can be regarded as being linear over this dosing range. FP was extensively distributed within the body ( V _ss 318  l), rapidly cleared (CL 1.1 l min⁻¹) with a terminal elimination half-life of 7.8  h and a mean residence time of 4.9  h.
3 In order that future pharmacokinetic/pharmacodynamic and other modelling can be carried out, the plasma concentration-time profiles were parameterized using a model based on sums of exponentials, the appropriateness of this model was justified as the secondary kinetic parameters from the model were similar to those obtained using non-compartmental analysis.     

HPLC法测定盐酸多沙普仑注射液中盐酸多沙普仑的含量

目的应用HPLC法测定盐酸多沙普仑注射液中盐酸多沙普仑的含量。方法色谱柱为依利特KromasilC18（5μm,4．6mm×250mm）,流动相为0．82g·L^-1醋酸钠溶液（用冰醋酸调pH值为4．5）-乙腈=71b：30,流速为1．0ml·min^-1,检测波长为214nm,柱温为室温。结果盐酸多沙普仑在12．87～90．12mg·L“范围内,浓度与峰面积线性关系良好（r=0．9997）;平均回收率为98．96％,RSD=0．44％（n=9）。精密度实验RSD分别为0．85％（n=6）。结论该方法测定结果准确、灵敏、可靠。     

Pharmacokinetics of ornidazole in neonates and infants after a single intravenous infusion

Summary The single dose pharmacokinetics of ornidazole has been evaluated in 12 neonates or infants (aged 1 to 42 weeks) after the infusion of 20 mg/kg over 20 min. Plasma disposition was described by a two-compartment open model. The distribution phase was short (T_1/2 (1)=0.31 h) and was followed by an elimination phase (t_1/2 (2)=14.67 h). The mean apparent volume of distribution was 0.96 l/kg^–1. These results did not differ from data previous by reported in adults. Total plasma clearance was between 0.4 and 1.4 ml·min^–1·kg^–1. The plasma concentration 24 h after the infusion was 7.32 mg·l^–1, which was above the minimum inhibitory concentration for clinically significant anaerobic bacteria. Based on the pharmacokinetic results and residual concentrations at 24 h, a single daily infusion of ornidazole 20 mg·kg^–1 appears adequate for therapy in neonates and infants.     

盐酸多沙普仑在中国蒙古族和汉族健康人体内的药动学特征

目的研究盐酸多沙普仑注射剂在汉族和蒙古族健康志愿者体内的药动学特征。方法 20名健康志愿者（蒙古族和汉族各10名,男女各半）,单次静脉滴注盐酸多沙普仑注射剂50 mg,采用HP代法测定血药浓度,DAS 2.0软件程序计算药动学参数并采用SPSS 13.0软件进行统计学分析。结果蒙古族受试者主要药动学参数为ρmax（1.03±0.30）mg·L^-1,t1/2（4.30±3.20）h,Vd（1.80±0.85）L·kg^-11,AUC0→12（2.47±0.80）mg·h·L^-1,AUC0→∞（2.89±1.06）mg·h·L^-1。汉族受试者主要药动学参数为ρmax（1.55±0.52）mg·L^-1,t1/2（3.87±2.17）h,Vd（1.35±0.96）L·kg^-1,AUC0→12（3.51±1.26）mg·h·L^-1,AUC0→∞（4.06±1.44）mg·h·L^-1。结论经统计学分析,多沙普仑在蒙古族和汉族受试者体内的药动学参数AUC0→12,ρmax差异有统计学意义,其他参数差异无统计学意义。     

Serum doxapram and respiratory neuromuscular drive in normal man

Summary To investigate the means by which doxapram affects the control of ventilation, ventilatory function and P_0.1 have been related to serum doxapram concentration during a 45-min infusion of doxapram hydrochloride in 7 healthy, conscious subjects under normoxic conditions.Serum doxapram concentrations increased during the infusion: 1.88, 2.48, 3.42, and 3.97 µg/ml after 5, 10, 30 and 45 min, respectively. The majority of significant changes in the measurements from the baseline were observed at 30 and 45 min: , V_T, P_0.1, P_0.1/end-tidal CO₂ tension, V_T/T_i and blood pressure were increased, and end-tidal CO₂ tension was decreased.No significant changes in Pdi_max, T_i/T_tot, /P_0.1, and P_0.1/(V_T/T_i) were observed. A correlation was observed between the % increases in P_0.1 and and doxapram concentration, and between and P_0.1.The doxapram-induced increase in appears to be caused by increased neural drive. It is related to the serum drug concentration in the conscious subject.     

The pharmacokinetics of oxpentifylline in man when administered by constant intravenous infusion

Summary Subjects were each given either a 25, 50 or 100 mg intravenous loading dose of oxpentifylline followed by an intravenous infusion at a constant rate of 1.5 mg/min for 3 h. Plasma levels of oxpentifylline were measured to obtain information on its pharmacokinetics and to establish which of the loading doses gave the most rapid attainment of the steady state plasma levels of intact drug. Oxpentifylline kinetics were best described by a two compartment model giving a characteristic dip in the plasma level versus time curves before steady state was reached when either the 50 or 100 mg loading doses, followed by the constant intravenous infusion, were given. The terminal half-life of oxpentifylline was 1.02±0.86 h, reflecting a very high clearance of the drug (approx. 3 000 to 6 000 ml/min). The high clearance could be attributed to extrahepatic metabolism occurring in blood which was observed in vitro using whole blood but not plasma. The clearance of a reduced metabolite of oxpentifylline was less than that of the intact drug, although the half-life was similar (0.83±0.18 h). Of the three loading doses tested, only the highest showed any side effects, these being transient and occurring within a 5 to 10 min period after dosing and appeared to correlate with the high initial plasma levels of the drug. The 25 mg loading dose gave initial plasma levels generally below the final steady state levels, whilst the 50 mg loading was the closest to giving immediate steady state plasma levels of oxpentifylline.Also known as PENTOXIFYLLINE     

The concentration-dependent disposition and kinetics of inulin

Summary The disposition of inulin was studied in 30 healthy male and 10 healthy female volunteers, and 10 patients with stable chronic renal failure (mean creatinine clearance 45 ml·min^–1) following intravenous infusion of 70 mg·kg^–1 over 5 min.Plasma concentrations fell rapidly initially but the rate of decline decreased continuously over 8 h and a linear terminal elimination phase could not be identified. Inulin was excreted rapidly by the subjects with normal renal function and 97.3% of the dose was recovered in the urine in 8 h. There was a progressive highly significant fall in the renal clearance of inulin after 2 h as plasma concentrations fell below about 150 mg·l^–1. Six to 8 h after administration the clearance was less than 50% of the initial value in the healthy volunteers and the corresponding fall in the renal patients was 33%.The concentration-dependent renal clearance of inulin was confirmed in step-up and step-down constant infusion studies in which clearances were measured at mean plasma concentrations ranging from 35.2 to 186.7 mg·l^–1. These studies virtually excluded time, changes in posture and urine flow rate as important factors. There was no statistically significant fall in clearance during the first 2 h and kinetic analysis was based on data obtained over this time. Under these conditions the mean plasma half life, volume of distribution (V_ss) and total body clearance of inulin in the healthy males, healthy females and patients with chronic renal failure were 73.2, 65.5 and 172.4 min, 10.5, 9.6 and 8.81·70 kg^–1 and 113.3, 111.5 and 43.3 ml·min^–1·70 kg^–1 respectively. There were no sex differences in any of the kinetic variables.The mechanism of the concentration-dependent clearance of inulin is unknown but the findings are consistent with saturable renal tubular reabsorption. Care is required with the use of inulin for measurement of the glomerular filtration rate by the single injection technique.     

Elimination rate ofN-acetylprocainamide after a single intravenous dose of procainamide hydrochloride in man

Equations were derived which made it possible to determine the elimination rate of N -acetylprocainamide from urinary data after intravenous administration of procainamide hydrochloride. A single dose of 500 mg of the drug was infused intravenously in four healthy subjects. On the basis of those equations, the formation rate of the metabolite could be calculated presuming that all rate processes were occurring by first-order processes. However, close examination of the excretion rate data appears to support the contention that the formation or excretion of N -acetylprocainamide may be occurring by a saturable process.     

Pharmacokinetics and safety of l-carnitine infused i. v. in healthy subjects

Summary The pharmacokinetics and safety of a brief i. v. infusion of l-carnitine 0, 20, 40 and 60 mg/kg have been investigated in 10 healthy subjects.The diurnal intraindividual variability of plasma carnitine was small (C. V.=3.0, 3.9 and 3.9%, respectively), and the total 24 h excretion in urine was also small and relatively constant: 4.6, 21.5 and 13.0 mg/day in the controls vs 4.6, 20.2 and 6.0 mg/day during treatment in the three subjects to whom saline alone was administered according to a single-blind design. Therefore, the pre-dose level of carnitine was subtracted from the level after dosing for the pharmacokinetic analysis. Plasma carnitine fitted well to a three-compartment open model, with Vc of 0.11–0.20 l/kg and a t_1/2 of 10–23 h. The urine recovery in 24 h was 77.2–95.4%.There were no objective or subjective side-effects attributable to carnitine, so its i. v. infusion is considered to be safe.     

Determination of pharmacokinetic parameters of vitamin K1 in rats after an intravenous infusion

Pharmacokinetic parameters of vitamin K1 have a large range of values in different literature. The aim of this study was to determine the pharmacokinetic parameters of vitamin K1 following post-constant speed intravenous infusion (PCSII) to provide rational pharmacokinetic parameters of vitamin K1 and compare these with results of noncompartmental analysis following intravenous injection (IV). After 15 hours intravenous infusion of vitamin K1 in rats, the logarithmic concentration–time curve of vitamin K1 was fit to a linear equation following PCSII (R² = 0.9599 ± 0.0096). Then, half-time (T_1/2), apparent volume of distribution (V_d), and clearance rate (CL) were estimated successively. T_1/2 of vitamin K1 was 4.07 ± 0.41 hour, CL was 89.47 ± 3.60 mL/h, and V_d was 525.38 ± 54.45 mL in rats following PCSII. There was no significant difference in pharmacokinetic parameters of vitamin K1 among different sampling times. For noncompartmental analysis, T_1/2 and mean residence time (MRT_INF) for a sampling duration of 6h were shorter than those of 12 hours or 24 hours sampling duration following IV (P < .05, P < .01). In addition, T_1/2 of vitamin K1 was obviously different from MRT-equated half-time (T_{1/2, MRT})(P < .05). V_d and CL of vitamin K1 following PCSII were larger than those following IV based on noncompartmental analysis (P < .01). The results demonstrated that drug distribution in the body was balanced and the Napierian logarithmic concentration–time curve of vitamin K1 fit to a linear equation following PCSII. Vitamin K1 has a long T_1/2 and a relatively large V_d following PCSII.     

氨茶碱和多沙普仑减轻布托啡诺术后镇痛期嗜睡的比较

目的:观察氨茶碱或多沙普仑对布托啡诺术后镇痛期嗜睡和镇痛效果(VAS评分)的影响。方法:全组均为硬膜外麻醉后,随机分为0.01%布托啡诺和0.25%氨茶碱镇痛泵组(简称组Ⅰ,n=35),0.01%布托啡诺和0.15%多沙普仑镇痛泵组(简称组Ⅱ,n=35)和0.01%布托啡诺镇痛泵组(简称组Ⅲ,n=35)。比较术后镇痛效果和副作用。结果:3组均获得了满意的术后镇痛效果。镇静评分(OAA/S,术后8~24 h):组Ⅲ>组Ⅰ和组Ⅱ(分别P<0.01)。SpO2(负荷剂量后0~30 min):组Ⅲ分别<组Ⅰ和组Ⅱ。VAS评分(术后8~24 h):组Ⅲ<组Ⅰ、组Ⅱ(P<0.01),但3组VAS评分均≤3分,且D1/D2值3组互比P>0.05。其它副作用差异无统计学意义。结论:氨茶碱或多沙普仑和布托啡诺合用能有效地减轻或消除布托啡诺术后镇痛期的嗜睡不良反应,提高了临床用药的安全性。     

多沙普仑在中国回族和汉族健康人体内的药动学

目的:研究汉族和回族健康受试者单次静脉滴注盐酸多沙普仑后的药动学。方法:回族和汉族健康受试者各10名,单次静脉滴注盐酸多沙普仑50 mg,定时采血,用HPLC法测定多沙普仑血药浓度,DAS 2.0软件计算药动学参数。结果:回族受试者的主要药动学参数为:cmax(1.48±0.46)μg/mlt、1/2β(3.91±2.05)h、Vd(1.35±0.45)L/kg、AUC0~12(3.02±0.56)μg·h·ml-1、AUC0~∞(3.49±0.73)μg·h·ml-1。汉族受试者的主要药动学参数为:cmax(1.55±0.52)μg/mlt、1/2β(3.87±2.17)h、Vd(1.35±0.96)L/kg、AUC0~12(3.51±1.26)μg·h·ml-1、AUC0~∞(4.06±1.44)μg·h·ml-1。结论:经统计学分析,回族和汉族健康受试者单次静脉滴注盐酸多沙普仑后药动学参数的差异无统计学意义。     

Pharmacokinetics of amitriptyline infused intravenously in man

Summary Amitriptyline was given to four male volunteers by constant rate intravenous infusion. Blood samples were collected before, during and at various times after the infusion for estimation of the serum concentrations of amitriptyline. The level of nortriptyline never reached a detectable level. A two compartment open model was shown to be applicable to the data obtained. The meaning of the parameters obtained by a non-linear, least squares curve fitting procedure is discussed and the values are compared to those recently published for nortriptyline. The calculated biological half-life of amitriptyline was about 17 hours, a figure which differs considerably from previously calculated values for volunteers, but is in accordance with some newer results from patients.     

Pharmacokinetic profile of intravenous miconazole in man

Summary The pharmacokinetic profile of miconazole has been studied in normal subjects and in patients suffering from severe renal insufficiency; one group of patients was undergoing intermittent haemodialysis. A three-compartment open model was fitted to the observed plasma concentrations obtained after intravenous infusion of miconazole 522 mg over fifteen minutes. The rate constants of elimination and exchange between compartments computed for the three groups were not significantly different. The apparent volumes of distribution in the cases of renal failure not undergoing haemodialysis were significantly smaller than the corresponding control values. A computational procedure is described which reduces observations obtained after infusion to the case of a single rapid intravenous administration.     

On the dose dependency of Cyclosporin a absorption and disposition in healthy volunteers

The pharmacokinetics of Cyclosporin A (CyA, Sandimmune^R) was studied in 12 healthy male volunteers after oral dosing of 350 mg, 700 mg, and 1400 mg as a drinking solution. Blood samples were collected over 96 hr and analyzed by high pressure liquid chromatography. Concentration data were evaluated with model-independent and model-based linear pharmacokinetic concepts. Individual CyA concentration-time profiles in whole blood were well described by a two-compartment open model with zero-order absorption for all three doses. Comparison of pharmacokinetic parameters across doses indicates that both absorption and disposition are dose-dependent. Nonlinear disposition is suggested by the significant increase of the terminal half-life from 8.9±4.9hr to 11.9±4.9hr (mean±SD) after a 350 mg and a 1400 mg dose, respectively. Changes in the metabolic activity of the liver with concentration might be responsible for this phenomenon. In addition, the modeling approach indicated that bioavailability decreases with increasing dose. Moreover, the dependence of the rate of CyA absorption (zero-order rate constant) versus dose was well described by a hyperbola. The limited solubility of the drug in the gastrointestinal tract might be responsible for this behavior. The lag time (0.2–0.8 hr) was independent of dose. This value is similar to the time of gastric emptying in fasting volunteers. The duration of absorption for 11 of 12 subjects was in the range 2.5–3.5 hr over all doses and agrees well with the small intestine transit time. Some subjects showed a marked secondary peak at one or two doses, which could be adequately fitted by a model with two successive zero-order inputs. This double-peak behavior was ascribed to the influence of the food on gastric emptying. Dose dependency of disposition and absorption counterbalance each other in the usual dose range. This leads to an almost proportional increase of area under the blood CyA concentration-time profile with increasing dose.Part of this work was presented at the Third European Congress of Biopharmaceutics and Pharmacokinetics, Freiburg i.Br., Germany, 1987.This work is part of the doctoral dissertation of Jean-Philippe Reymond.Partly supported by Contrat de prestation 84112 between INSERM and Sandoz.     

Pharmacokinetics of antofloxacin hydrochloride in healthy male subjects after multiple intravenous dose administration

1. The purpose of the study was to evaluate pharmacokinetic characteristics of antofloxacin hydrochloride, a new fluoroquinolone antibiotic, during a multiple, intravenous dosing regimen.

2. Twelve healthy, Chinese male volunteer subjects were each given 300?mg of antofloxacin by intravenous infusion once daily for 7 days. Blood and urine samples were taken at designated time points for analysis of antofloxacin concentration by high-performance liquid chromatography (HPLC). Safety and tolerability were assessed by evaluation of subject complaints, vital signs, electrocardiograms, electroencephalograms, clinical chemistry parameters, haematology and urinalysis and prothrombin time.

3. The serum steady concentration of antofloxacin was obtained in 96?h after the administration of a daily intravenous dose of 300?mg of the drug. In the present study, the following pharmacokinetic parameters after 7 days of treatment with antofloxacin were determined to be: C_max 3.81?±?0.66?mg/L, C_min 0.85?±?0.19?mg/L, AUC_0–24 60.51?±?8.30?mg/L·h, C_av 2.52?±?0.35?mg/L, PTF 87.45?±?3.37%, t_1/2β 20.34?±?1.88?h. The C_max and AUC_0–24 after 7-day treatment were both higher than after the first dose (by 43% and 110%, respectively). The cumulative urinary elimination of antofloxacin within 96?h after the last dose was about 56%.

4. During the study, there were neither subject complaints nor significant adverse clinical findings.

5. Antofloxacin, administered intravenously as a single, daily 300?mg dose for 7 days, demonstrated favourable pharmacokinetic characteristics and tolerability. The results of this study indicate that antofloxacin hydrochloride is suitable for further clinical study.

     

The physiological disposition of etilefrine in man

Summary Pharmacokinetic and metabolic studies with³H-etilefrine were performed to assess the importance of a first-pass effect on the pharmacodynamic action of this sympathomimetic amine. Identical amounts of³H-activity, ca. 80% of the dose, were excreted in the urine after intravenous or oral administration, which indicates complete enteral absorption of the drug. Comparison of the areas under the plasma curves of unchanged etilefrine after both routes of administration resulted in a bioavailability factor of 0.55, which can be explained by an extensive first-pass effect. The time curve of plasma levels of etilefrine was compatible with an open 2-compartment model characterized by a rather large volume of distribution (V_d, ) of 160 1, and a predominant half life of 2 hours. The pharmacodynamic action corresponded to the amount of drug in the central compartment. The major pathway of metabolism of etilefrine was conjugation to form the phenolic sulphate, and a very minor proportion of the drug was excreted as the corresponding hydroxymandelic acid. This metabolic pattern seems to confirm our hypothesis that phenylalkylamines with the hydroxyl group in the m-position of the benzene ring are predominantly conjugated in contrast to p-hydroxylated compounds which are mainly deaminated.Parts of these results have been presented as a thesis for the MD degree of the University of Giessen