Effects of the rate and composition of fluid replacement on the pharmacokinetics and pharmacodynamics of intravenous furosemide

Effects of differences in the rate and composition of intravenous fluid replacement for urine loss on the pharmacokinetics and pharmacodynamics of furosemide were evaluated using the dog as a model animal. Each of six dogs received 8-hr constant intravenous infusion of 20 mg (15 mg used in one dog) of furosemide with 0% replacement (treatment I), 50% replacement (treatment II), and 100% replacement (treatment III) with lactated Ringer's solution, as well as with 100% replacement with 5% dextrose in water (treatment IV). Most pharmacokinetic parameters, such as plasma clearance, steady-state volume of distribution, mean residence time, and terminal half-life, were essentially the same in all four treatments. Renal clearances and urinary excretion rates of the drug in treatments II–IVwere essentially the same, but about 20% higher than those in treatment I.In spite of the similarities in kinetic properties, diuretic and/or natriuretic effects from furosemide were markedly different among the four treatments. For example, mean 10-hr urine outputs were 646, 1046, 3156, and 1976 ml and mean 10-hr sodium excretions were 87.0, 142, 383, and 97.2 mmole for treatments I–IV,respectively. Except for treatment III,diuresis and/or natriuresis were found to be time-dependent, generally decreasing with time until reaching a low plateau during later hours of infusion. The present findings also showed that (1)no fluid replacement and 100% replacement with 5% dextrose solution both produced the same degree of severe acute tolerance in natriuresis, indicating the insignificance of water compensation in tolerance development; (2)in treatment II,where neutral sodium balance was achieved, the development of acute tolerance in diuresis and natriuresis can mainly be attributed to negative water balance under this special condition; (3)at steady state the hourly diuresis and natriuresis could differ up to about ten times between treatments. Some implications for the kinetic/dynamic relationship or modeling, in the clinical use, and in the bioequivalence evaluation of dosage forms are discussed.     

Pharmacokinetics of ketanserin in patients with essential hypertension

Summary The pharmacokinetics of ketanserin and its main metabolite ketanserin-ol, and the antihypertensive effects of intravenous, single oral and chronic oral (40 mg once daily) administration of ketanserin, have been investigated in a single blind study of 10 patients with uncomplicated mild hypertension. Ketanserin had a terminal half-life of 29.2 h, a plasma clearance of 518 ml/min and a volume of distribution of 18.0 l/kg. Chronic oral intake of 40 mg ketanserin (tablet formulation) gave a peak concentration of unchanged ketanserin of 88 ng/ml after 1.1 h. Its absolute bioavailability was 48%.During chronic therapy the maximal concentration of ketanserin-ol was 208 ng/ml and its half-life of elimination was 35.0 h. As this metabolite can be oxidized back to ketanserin, it contributes to the prolonged half-life of unchanged ketanserin seen during chronic therapy.The blood pressure was reduced by approximately 15% by oral ketanserin. The maximal reduction in blood pressure coincided with the peak concentration of unchanged ketanserin. During chronic therapy with 40 mg once daily blood pressure was reduced over 24 h. The heart rate was slightly reduced and the cardiovascular responses and the plasma noradrenaline concentrations during isometric exercise were only slightly influenced by ketanserin therapy.Thus, unchanged ketanserin has a relatively long half-life during chronic oral therapy and its pharmacokinetics in middle-aged hypertensive patients is similar to that in normal young volunteers.     

Pharmacokinetics of peptide T in patients with Acquired Immunodeficiency Syndrome (AIDS)

1. The pharmacokinetics of Dalal-peptide T-NH2 (peptide T) was determined during phase I clinical trials in patients with acquired immunodeficiecy disease (AIDS) and AIDS related complex (ARC). Drug levels were determined by specific RIA, and in some cases with HPLC analysis, after intraveneous (i.v.) or intranasal (i.n.), via metered sprayer, administration.

2. The plasma kinetics appeared to be bi-phasic with a first compartment half-life of 30 to 60 minutes and a second plasma clearence rate of 4 to 6 hours, observed for both routes of administration. Peptide T, in one individual was confirmed to be present at 6 hrs in plasma, determined after HPLC isolation followed by specific RIA.

3. Bioavailabilty, determined for a 2 mg test dose in six individuals was 9.3 ± 6.9 nmol/L. Peak plasma levels of 41 ± 30 nmol/L after 10 mg i.n., 2.8 ± 5.9 nmol/L after 2mg i.n., and 0.13 ± 0.07 nmol/L after 0.4 mg i.n. were observed. In two individuals tested, peptide T was detected in CSF at levels 20% of the corresponding plasma level 90 and 145 minutes post i.v. administration. Peptide T was not detected in urine. I.N. administration was well tolerated for times up to 21 months.     

Effect of cirrhosis and renal failure on the kinetics of clotiazepam

Summary The kinetics of a single 5-mg oral dose of the thienodiazepine clotiazepam was evaluated in a series of patients with biopsy-proven cirrhosis, and in patients with renal insufficiency requiring maintenance hemodialysis, compared to healthy matched controls. Clotiazepam volume of distribution (V_z) was significantly smaller in cirrhotic patients than in controls (1.83 vs 2.57 l/kg), and total clearance was likewise reduced (2.15 vs 3.15 ml/min/kg). Elimination half-life was similar between groups (10.0 vs. 10.2h). There were no significant differences between renal failure and control patients in clotiazepam V_z, oral clearance, or elimination half-life. Thus cirrhosis is associated with reduced clearance of clotiazepam, probably due to impairment of its microsomal oxidation. However clotiazepam disposition is not significantly altered in dialysis-dependent renal insufficiency patients.Supported in part by Grant OC 10/6–4 from Deutsche Forschungsgemeinschaft, and Grant MH-34223 from the United States Public Health Service.     

法莫替丁冲剂在健康人中的生物利用度及药动学研究

本实验采用反相高效液相色谱法，比较了１０名健康志愿者单剂量口服法莫替丁冲剂及等剂量片剂的生物利用度。结果表明：二种剂型的Ｔｍａｘ，Ｃｍａｘ，ＡＵＣ均无显著性差异（Ｐ〉０．０５）。冲剂相对于与片剂的相对生物利用度Ｆ＝１０１．９０。     

Phase I Study of Paclitaxel by Three-hour Infusion: Hypotension Just after Infusion Is One of the Major Dose-limiting Toxicities

The primary objectives of this study were to determine the maximum tolerated dose (MTD) of paclitaxel administered by 3-h infusion to patients with solid tumors, and to characterize the pharmacokinetics of a 3-h infusion in comparison with those of a 24-h infusion. Twenty-seven patients each received one of six levels of paclitaxel, 105, 135, 180, 210, 240 and 270 mg/m², with premedication. Two patients given 240 mg/m² and one patient given 270 mg/m² unexpectedly had grade 3/4 hypotension just after finishing the paclitaxel infusion. Peripheral neuropathy was also dose-limiting at 270 mg/m². Although granulocytopenia was significantly less severe than with a 24-h infusion, more than half of the patients experienced grade 4 toxicity at doses of 240 or 270 mg/m². Severe hypersensitivity reactions (HSRs) were not observed. Pharmacokinetic studies using high performance liquid chromatography demonstrated proportionally greater increases in the peak plasma concentration and area under the curve, and decreases in clearance and volume of distribution with increasing dose, suggesting non-linear pharmacokinetics of paclitaxel when given by 3-h infusion. The MTD of paclitaxel given as a 3-h infusion was determined to be 240 mg/m² with dose-limiting toxicities of granulocytopenia, peripheral neuropathy and hypotension. Hypotension just after infusion, induced by 3-h infusion of paclitaxel, is a new observation which has not been reported previously. The recommended dose for phase II study is 210 mg/m². Although hypotension was observed as an unexpected toxic effect, paclitaxel could be administered safely over 3 h with premedication and proper monitoring, resulting in reduced myelotoxicity and with no increase in the incidence of HSRs as compared with a 24-h infusion.     

Pharmacokinetics of intravenously administered sodium dichloroacetate in rabbits

ＰｈａｒｍａｃｏｋｉｎｅｔｉｃｓｏｆｉｎｔｒａｖｅｎｏｕｓｌｙａｄｍｉｎｉｓｔｅｒｅｄｓｏｄｉｕｍｄｉｃｈｌｏｒｏａｃｅｔａｔｅｉｎｒａｂｂｉｔｓＧｕＢｉｎ（顾斌）；ＳｏｎｇＬｉｎｇ（宋岭）；ＪｉａｎｇＹｏｎｇｐｅｉ（蒋永培）；ＷｅｎＡｉｄｏｎｇ（文...     

人体中氧氟沙星的立体选择性代谢

５名健康志愿者日服单剂３００ｍｇ氧氟沙星［（±）－Ｏｆ１］后，采用立体选择性的ＲＰ－ＨＰＬＣ手性流动相添加剂法测定尿中Ｓ－（－）－Ｏｆ１和Ｒ－（＋）－Ｏｆ１浓度结果显示Ｏｆ１在人体内呈现立体选择性代谢。尿中排泄的Ｓ－（－）－Ｏｆ１／Ｒ－（＋）－Ｏｆ１之比随时间变化。服药后２ｈＳ／Ｒ是０．８７５，２４ｈ增加到１．１５０．Ｓ－（－）－Ｏｆ１的消除半衰期（ｔ１／２）是４．５７ｈ；消除速率常数（ｋ）是０．１５４ｈ；药时曲线下的面积（ＡＵＣ）为１．１７ｍｇ·ｈ－１．ｍＬ－１；Ｒ－（＋）－Ｏｆ１的ｔ１／２为４．１８ｈ，ｋ为０．１６８ｈ－１，ＡＵＣ是１．７８ｍｇ·ｈ－１·ｍＬ－１；经配对ｔ检验这三对参数间有显著性差异，Ｐ值分别小于０．０１，０．００１和０．００５．因此两对映体在人体内呈现立体选择性处置     

Effect of concomitant food intake on absorption kinetics of fenoldopam (SK&F 82526) in healthy volunteers

Summary Eight healthy volunteers participated in an open crossover study to assess the effect of a standardised meal on the systemic availability of a single oral dose of fenoldopam mesylate 100 mg. Subjects were studied on four separate occasions, twice fasting and twice fed in randomised, balanced order. Plasma and urine samples were obtained before and at regular intervals up to 25 h post dose. Measurement of fenoldopam (SK&F 82526) and its 8-sulphate metabolite (SK&F 87782) were by means of HPLC-EC analysis. Area under the plasma concentration time curve (AUC) and maximum detected plasma concentration (C_max) for fenoldopam and SK&F 87782 were significantly reduced whereas time to maximum concentration was significantly increased with food. Using AUC's for fenoldopam and SK&F 87782, mean relative bioavailabilities were 35% and 81% respectively under fed compared with fasting conditions. Twenty-four hour excretion of fenoldopam was significantly reduced with food, but excretion of SK&F 87782 was apparently unchanged. Mean relative bioavailabilities calculated from these data were 83% and 86% respectively. Relatively large inter-subject variability in AUC and C_max were seen, but intra-subject variability was not marked. Mild symptoms associated with vasodilation were reported on all study days.     

Pharmacokinetic and -dynamic studies in elderlies with a potential antihypoxidotic/nootropic drug tenilsetam utilizing pharmaco-EEG and psychometry

In a double-blind, placebo-controlled study, the pharmacokinetic, encephalotropic, and psychotropic properties of a new metabolically active thienyl-piperazine derivative were studied in ten elderly subjects in their sixties by means of quantitative EEG and psychometric analyses. At weekly intervals, they received randomized single oral doses of placebo; 75 mg, 150 mg, and 300 mg tenilsetam (CAS 997); and 3.2 g piracetam as reference drug. Blood sampling EEG recordings, psychometric and psychophysiological tests, as well as the monitoring of blood pressure, heart rate, and side effects were carried out at 0, 2, 4, 6, 8, and 24 hr. Pharmacokinetic investigations showed that CAS 997 was rather well absorbed, as peak concentrations were observed consistently at 2 hr and were clearly dose-dependent. The terminal half-life was between 18 and 22 hr, as compared with 6 hr for the reference drug piracetam, which also exhibited plasma peaks at 2 hr. Computer-assisted spectral analyses of the EEG showed a significant CNS effect of CAS 997 as compared with placebo, characterized by an increase of alpha activity, decrease of delta activity, and fast beta activity, as well as by tendency towards an augmentation of total power and decrease of the centroid and centroid deviation of the total beta activity. Partly similar though less pronounced alterations were exhibited by 3.2 g piracetam. Such changes were described previously by us after several other antihypoxidotics/nootropics and are indicative of improvement in vigilance. Dose/treatment–efficacy calculations demonstrated 75 and 150 mg CAS 997 superior both to placebo and the reference compound but also to the highest given dosis (300 mg CAS 997). Time–efficacy calculations showed two pharrnacodynamic peaks: one in the 4th and another one in the 8th to 24th hour. The time lag between pharmacokinetic and -dynamic changes may be due to the penetration of the drug through the blood brain barrier to a deep compartment receptor as well as to the formation of active metabolites. Psychometric investigations showed only small and inconsistent psychotropic effects after single doses of CAS 997 in elderlies. Evaluation of pulse rate, blood pressure, and side effects showed a good tolerability of both drugs.