Effect of age on the pharmacokinetics of vinpocetine (Cavinton) and apovincaminic acid

Summary The pharmacokinetics of vinpocetine and its main metabolite, apovincaminic acid (AVA), were studied in the aged. Vinpocetine was eliminated with a mean half-life of 2.12±0.51 h. Total plasma clearance (CL) and distribution coefficient () of the parent drug were 2.2±0.9 l · kg^–1 · h^–1 and 6.7±3.7 l · kg^–1, respectively. The CL and of vinpocetine differed significantly from young subjects but the elimination half-life was not altered. Significant changes in the elimination half-life and plasma clearance of AVA were found, perhaps because of the physiological decrease in renal function.     

Relationship between inflammation and infliximab pharmacokinetics in rheumatoid arthritis

Aims

Infliximab, an anti-tumour necrosis factor-α monoclonal antibody, is indicated in rheumatoid arthritis (RA). Our objective was to evaluate the influence of the sources of infliximab pharmacokinetic variability in RA.

Methods

Eighty-four patients treated with infliximab for RA were included in a prospective noncomparative study. They were analysed between two consecutive infliximab infusions. Infliximab concentrations were measured before the infusion, 2 h, 1 and 4 weeks after the infusion and immediately before the next infusion. Infliximab concentrations were described using a two-compartment population pharmacokinetic model.

Results

The mean (interindividual standard deviation) estimated central volume of distribution was 2.3 l (36%) and systemic clearance was 0.019 l h⁻¹ (37%). The central volume of distribution increased with bodyweight; it was doubled between 50 and 90 kg. Systemic clearance increased with pre-infusion C-reactive protein concentration by 20%, varying from 3 to 14 mg l⁻1, and was decreased by 30% when methotrexate was coadministered.

Conclusions

The influence of methotrexate and inflammation on infliximab clearance suggests that individual adjustment of infliximab doses according to disease activity may be useful in RA.     

Salicyl phenolic glucuronide pharmacokinetics in patients with rheumatoid arthritis

Summary The pharmacokinetics of salicyl phenolic glucuronide (SPG) and other salicylic acid (SA) metabolites were studied at three aspirin dosage regimens in eight patients with rheumatoid arthritis. Each patient received 1, 2 and 4 g enteric coated aspirin (ASA) daily in ascending order. At the end of each 2-week dosage period, plasma and urine were collected over a dosage interval for the estimation of various pharmacokinetic parameters. With increasing ASA dosage, mean clearance of SA to SPG was approximately constant (1.8±0.3, 1.7±0.2, and 1.5±0.2 ml/min at 1, 2 and 4 g/day, respectively) when related to plasma concentrations of total SA. The percentage of the ASA dosage recovered in urine as SPG increased from 5.2±1.1 to 7.1±1.1 to 10.5±1.7 at 1, 2 and 4 g/day, respectively. It was concluded, however, that the conversion of SA to SPG is saturable, since the mean clearance of SA to SPG decreased when calculated with respect of the plasma concentration of unbound SA (13.4±1.6, 11.0±1.4, and 6.6±1.9 ml/min at 1, 2 and 4 g/day, respectively). The kinetics of the formation and excretion of salicylurate and the excretion of gentisate were similar to those found in previous studies.     

The pharmacokinetics of diclofenac sodium in patients with active rheumatoid disease

Summary Pharmacokinetic data for diclofenac sodium has been well established in healthy volunteers, whereas in patients with rheumatoid arthritis very little information is available in the literature. A single oral dose of enteric-coated diclofenac sodium was given to 10 patients with active rheumatoid disease, adopting the same procedures used for a group of 10 healthy volunteers in whom pharmacokinetic data was already available. Plasma specimens were collected over a period of 8h following administration and concentrations of diclofenac determined by GLC. Resulting plasma concentration curves were similar to those obtained in the healthy subjects in that areas under curves and terminal half-lives were comparable. However, peak concentrations of diclofenac were significantly reduced in the rheumatoid patients. The lower peak concentrations were correlated with the lower serum albumin levels in the patients which are associated with active rheumatoid disease.     

Altered prazosin pharmacokinetics in congestive heart failure

Summary The pharmacokinetics of prazosin (Minipress^®) were studied in nine patients with NYHA Class 3 or 4 congestive heart failure and in five healthy controls. After a single 5 mg oral dose, plasma concentrations of prazosin, as reflected in the area under the plasma concentration-time curve (AUC) and prazosin plasma half-life, were approximately double in the patients in comparison to the control group. Reduction in hepatic blood flow, altered gastrointestinal absorption of the drug or diminished intrinsic hepatic metabolic activity in the patient group may have contributed to the observed changes in prazosin disposition. The finding of higher prazosin plasma concentrations in patients with refractory heart failure demonstrates the need for close monitoring of these individuals following administration of the drug in the treatment of chronic congestive heart failure.Sponsored by the National Institute of General Medical Sciences Training Grant GM 07546 and by a grant from Pfizer Corporation     

Influence of chronic diflunisal treatment on the plasma levels,metabolism and excretion of indomethacin

Summary The single-dose pharmacokinetics of indomethacin following 100 mg rectally was measured in two groups of 8 healthy subjects before and after diflunisal 500 mg p.o. once daily, or 500 mg in the morning and 1000 mg in the evening, until steady state conditions were reached. A further group of 8 healthy subjects was given 50 mg indomethacin rectally before and after diflunisal 500 mg p.o. twice daily.High dose diflunisal (1500 mg/day) decreased the renal clearance of indomethacin from 21.9 to 1.8 ml/min (92%) and reduced the renal excretion of both unchanged (63%) and conjugated (82%) indomethacin. The apparent total body clearance (0.12 l/h/kg), apparent volume of distribution (0.98 l/kg), and volume of distribution at steady state (0.80 l/kg) were decreased by 47%, 35% and 30%. The maximum plasma concentration (2.4 µg/ml) and total area under the curve (13.0 µg × h/ml) were increased by 40% and 119%, respectively. The terminal elimination half-life (5.7 h) and mean residence time (6.7 h) were slightly prolonged (7.0 h and 8.8 h) in the presence of diflunisal. The contribution of metabolism to the overall elimination of indomethacin was increased by only 2%.Similar results were obtained when the subjects were challenged with the low dose of diflunisal (500 mg/day), although the magnitude of the changes were smaller. The interaction between indomethacin and diflunisal may be due to competition both at the metabolic (conjugation) and the excretory (tubular secretion) levels.When the subjects were given 50 mg indomethacin and diflunisal 1000 mg/day simultaneously, the achieved maximum plasma concentration of indomethacin (2.53 µg/ml) was comparable to that seen after 100 mg in the absence of diflunisal (3.1 µg/ml), but the AUC was greater (21.7 µg × h/ml vs 13.0 µg × h/ml).Adverse central nervous reactions were more frequent and more pronounced at higher plasma indomethacin concentrations.     

老年患者和肾病患者口服阿替洛尔片的药物动力学研究

目的：测定阿替洛尔片的血药浓度，对健康壮年，老年及肾病志愿者进行药物动力学研究。方法；健康壮年及老年志愿受试者各８例，肾病志愿者５例，均为单剂量口服阿替洛尔片７５ｍｇ，用ＨＰＬＣ法测定。结果；药－时曲线符合一级吸收二室模型。健康壮年人的主要药动不参数为Ｋａ：１．０１ｈ＾－１，Ｔ１／２β：４．２８ｈ，Ｋ１０：０．２５ｈ＾－１，ＡＵＣ：５．２μｇ．ｈ．ｍｌ＾－１，ＣＬ／Ｆ：１４．９５ｍｇ．ｍｌ（μｇ．     

Influence of fluconazole on the pharmacokinetics of omeprazole in healthy volunteers

Influence of fluconazole on the pharmacokinetics of omeprazole was evaluated by single oral administration of omeprazole capsule 20 mg (control group), or single oral administration of fluconazole capsule, 100 mg, and omeprazole, 20 mg, after 4 days of daily oral administration of fluconazole, 100 mg (treated group), to 18 healthy male volunteers. Omeprazole is extensively metabolized in the liver through 5-hydroxylation and sulfoxidation reactions catalyzed predominantly by CYP2C19 and CYP3A4, respectively. Fluconazole is a potent competitive inhibitor of CYP2C19 and a weak inhibitor of CYP3A4. In treated group, the area under the plasma concentration-time curve of omeprazole from time zero to time infinity (AUC) was significantly greater (3090 vs 491 ng h/ml), terminal half-life of omeprazole was significantly longer (2.59 vs 0.85 h), and peak plasma concentration of omeprazole (C(max)) was significantly higher (746 vs 311 ng/ml) than that in control group. The greater AUC and higher C(max) in treated group could be due to inhibition of omeprazole metabolism by fluconazole.     

The pharmacokinetics of intravenous,intramuscular, and subcutaneous nalbuphine in healthy subjects

Summary The pharmacokinetics of intravenously, intramuscularly, and subcutaneously administered nalbuphine were studied in three parallel groups of 12 healthy volunteers each. The subjects received single doses of 10 mg and 20 mg of nalbuphine separated by a one week washout period. Blood specimens were obtained up to 15 h after dosing for determination of nalbuphine.Mean plasma nalbuphine concentrations 5 min after intravenous administration of 10 or 20 mg were 39 and 73 ng/ml, respectively. The mean maximum plasma concentrations (C_max) after intramuscular or subcutaneous administration of nalbuphine 10 mg were 29 and 31 ng/ml, respectively. Mean C_max values after 20 mg doses were 60 and 56 ng/ml. Mean C_max occurred 30 to 40 min after nalbuphine administration. The mean elimination half-lives of parenterally administered nalbuphine ranged between 2.2 and 2.6 h, regardless of dose given or route administered. The mean absolute bioavailability was 81% and 83% for the 10 and 20 mg intramuscular doses, respectively, and 79% and 76% following 10 and 20 mg of subcutaneous nalbuphine. The mean volumes of distribution (V_ss) of the intravenously administered drug were 290 and 274 l and the mean systemic clearances were 1.6 and 1.5 l/min following administration of 10 and 20 mg doses, respectively.Intramuscular and subcutaneous nalbuphine appear to be interchangeable based on the similarities in C_max, mean times until maximum concentration, mean AUC data, and absolute bioavailabilities.     

The effect of exercise on atropine pharmacokinetics

Summary Seven healthy males (19–32 y) underwent each of four separate conditions in a repeated measures design. Five of these subjects underwent an additional trial. In four of five trials subjects received 2.0 mg atropine sulfate intramuscularly in the anterolateral portion of the left thigh: at rest (T1); following completion of a single exercise (Ex) bout (T2), (Each bout consisted of 25 min of stationary cycling at 40% VO₂ max with 5 min of seated rest), prior to three Ex bouts (T3) and following one and prior to three Ex bouts (T5). Trial 4 (T4) was the same as T3 with the substitution of a saline placebo. Serum samples were collected over a 12 h period and atropine concentration was determined by RIA. Ex trials were compared to T1.Ex prior to atropine (T2) significantly decreased the mean volume of distribution (V_z, 278 vs 2321). Ex in T3 significantly decreased the serum half life (t_1/2, 4.2 vs 3.5 h), V_z (278 vs 1981), and clearance (CL, 763 vs 638 ml·min^–1) and significantly increased the peak concentration (Cp, 6.7 vs 12.3 ng·ml^–1) and area under the curve (AUC, 44.1 vs 53.1 ng·ml^–1). In T5, Ex significantly decreased the t_1/2 (3.4 h), V_z (182 l) and CL (575 ml·min^–1) and significantly increased the absorption rate constant (ka, 0.482 vs 1.1 min^–1), elimination rate constant (ke, 0.0012 vs 0.0015 min^–1), C_p (14 ng·ml^–1) and AUC (53.3 ng·h·ml^–1).These results demonstrate that moderate Ex either prior to and/or immediately following drug administration has the capacity to significantly modify atropine pharmacokinetics.Portions of this work were presented at the annual meeting of The American Society for Pharmacology and Experimental Therapeutics, Montreal, Canada, October 1988The opinions or assertions contained herein are the private views of the authors and are not to be construed as official or reflecting the opinions of the Department of the Army or the Department of Defense.     

Single and multiple dose pharmacokinetics of tenoxicam in the elderly

Summary Fourteen elderly subjects (10 women, 4 men) with a mean age of 81 (SD 6.7) years and in need of anti-inflammatory drug treatment were given a single dose of 20 mg tenoxicam. After a drug-free interval of 5 weeks, multiple dose treatment with 20 mg tenoxicam once daily for 56 days was initiated. The single and multiple dose kinetics of tenoxicam were investigated after HPLC determination of tenoxicam in the plasma.The elimination half-life of tenoxicam ranged from 44 to 132 h (mean 71.9 h) with no significant difference between the single and multiple dosage regimens. Tenoxicam reached maximum plasma concentrations after 1.4 and 1.1 h, with values of 3.6 and 15.5 µg·ml^–1, for the single and multiple dosage regimen respectively. The corresponding trough values (24-h values) were 1.8 and 11.7 µg·ml^–1. A mean accumulation ratio of 5.1 was calculated. The mean increase in the area under the plasma concentration time curves at steady-state was 21% more than predicted from the initial single dose. This deviation from linearity was considered to be of minor clinical significance. The kinetics of tenoxicam in elderly were similar to that published for young healthy volunteers.     

Influence of repeated administration of cimetidine on the pharmacokinetics and pharmacodynamics of adinazolam in healthy subjects

Summary Adinazolam is a new triazolobenzodiazepine bearing an alkyl-amino side chain. A cross-over double-blind placebo controlled study was carried out in 12 healthy volunteers, in order to check the possible interaction between cimetidine and adinazolam after repeated co-administration.Cimetidine or placebo were given during 17 days. Beginning on Day 8 of each treatment, adinazolam was given in the increasing doses following sequence of doses for 3 days: 10 mg b.i.d., 20 mg b.i.d. and 20 mg t.i.d. A pharmacokinetic and pharmacodynamic study was performed on the third day at each dose. A wash-out of three weeks was included between the two treatments.Cimetidine increased significantly the AUC values of both adinazolam and N-desmethyladinazolam, reduced the oral clearance of adinazolam, and prolonged adinazolam's half-life.The digit symbol substitution test was significantly affected at each dose level while the manual dexterity was marginally impaired by adinazolam plus cimetidine.Saftee-up interview and Clyde mood scale indicated an increased sedation under adinazolam plus cimetidine in four subjects.     

A review of the pharmacokinetics,tolerability and pharmacodynamics of amisulpride in healthy volunteers

Amisulpride binds selectively to dopamine D(2) and D(3) receptors in the limbic system. Low doses of amisulpride preferentially block presynaptic D(2)/D(3)-dopamine autoreceptors, thereby enhancing dopaminergic transmission, whereas higher doses block postsynaptic receptors, thus inhibiting dopaminergic hyperactivity. Amisulpride is clinically effective on the negative symptoms of acute schizophrenia exacerbations at low dosages (50-300 mg/day), and also on the positive symptoms of the disease at high dosages (400-800 mg/day). Nineteen clinical studies involving 358 volunteers have investigated the pharmacokinetics, pharmacodynamics and tolerability of amisulpride. Amisulpride shows linear pharmacokinetics, a bioavailability of 48%, low protein binding (17%) and an elimination half-life of approximately 12 h. It is predominantly eliminated in the urine as the parent compound. It exhibits no significant detrimental effects in psychometric or memory tests up to the dose of 400 mg/day, inducing only mild impairment at high doses, whereas EEG data suggest an alertness-enhancing effect at low doses (相似文献   

The pharmacokinetics of d-sotalol and d,l-sotalol in healthy volunteers

Summary The pharmacokinetics of d-sotalol has been studied in six healthy volunteers given single doses of 0.25, 0.50, 1, 2 mg·kg^–1 i.v. and one 100 mg oral dose in comparison with the kinetics of 1 mg·kg^–1 i.v. of dlsotalol.There was no significant difference in the disposition of the d-enantiomer and the racemate.The terminal half-life averaged 7.2 h, and the kinetics was linear, with a mean total clearance of 0.13 l·h^–1·kg^–1. Renal clearance of d-sotalol represented 56 to 77% of total clearance. The absolute systemic availability of oral d-sotalol was close to 100% and the elimination half-life of the oral-d-enantiomer was similar to that of the i.v. form (7.5 h).     

中老年牙周炎与类风湿关节炎相关性研究

目的通过血液细胞因子和血液成分分析,探讨中老年牙周炎与类风湿关节炎(RA)两种疾病发病机制的相关性。方法对26例局部侵袭性牙周炎(LAgP)、31例侵袭性牙周炎(GAgP)和21例RA以及对照组28名没有系统或口腔疾病的健康体检者(CTRL),使用酶联免疫吸附试验(ELISA)检测细胞因子白细胞介素(IL)-1α、IL-6和肿瘤坏死因子(TNF)-α以及其他血液成分白细胞计数和分类、血沉(ESR)、C反应蛋白(CRP)和类风湿因子(RF)。结果RA患者IL-1α、TNF-α水平高于对照组,两组比较差异有统计学意义(P<0.05);GAgP和RA患者相类似,TNF-α水平高于对照组,差异有统计学意义。另外,GAgP患者IL-6水平高于对照组,同时可见白细胞数和中性粒细胞升高;ESR和CRP、RF检测,两者和对照组比较差异均有统计学意义(P<0.01)。结论中老年牙周炎与RA发病机制具有密切相关性。     

The relationship between pharmacokinetics and pharmacodynamics of enoximone in healthy man

Summary The relationship between the pharmacokinetics and pharmacodynamics of enoximone, a new positive inotropic agent, was investigated in 6 healthy men. The volunteers received single oral and i.v. doses of 3 and 1 mg/kg, respectively, and placebo in a double-blind cross-over trial. Plasma concentrations of enoximone and its sulphoxide metabolite, effects on the corrected electromechanical systole (QS₂c), the impedance cardiogram (dZ/dt)/RZ index, blood pressure and heart rate were determined over an 8-h period.Peak effects on QS₂c and the (dZ/dt)/RZ index were obtained after approximately 1 h. During the first hour, the cardiac effects lagged behind the high plasma concentrations. Thereafter, the effects on QS₂c were closely correlated with the plasma concentrations both of enoximone and its sulphoxide derivative (r0.90). The concentration-effect curves of both substances were parallel and were independent of the route of administration. The inotropic activity was not related to the drug level in hypothetical peripheral compartments.The results suggest that determination of plasma enoximone 1 h after administration and thereafter may be useful in assessing the haemodynamic activity of the drug. Should this observation also be present in a clinical situation, plasma enoximone measurements might be a valuable tool in management of patients suffering from heart failure.     

Effects of Schisandra sphenanthera extract on the pharmacokinetics of tacrolimus in healthy volunteers

AIM: To assess the effect of Schisandra sphenanthera extract (SchE) on the pharmacokinetics of tacrolimus in healthy volunteers. METHODS: Twelve healthy male volunteers were orally treated with SchE, three capsules twice daily for 13 days. Pharmacokinetic investigations of oral tacrolimus administration at 2 mg were performed both before and at the end of the SchE treatment period. Whole blood tacrolimus concentrations were determined by enzyme-linked immunosorbent assay. Estimated pharmacokinetic parameters before and with SchE were calculated with noncompartmental techniques. RESULTS: Following administration of SchE, the average percentage increases of individual increases in AUC, AUMC and C(max) of tacrolimus were 164.2% [95% confidence interval (CI) 70.1, 258.4], 133.1% (95% CI 49.5, 261.3) and 227.1% (95% CI 155.8, 298.4), respectively (P < 0.01 or 0.05). On average, there was a 36.8% (95% CI 13.4, 60.2) increase in tacrolimus t(max) (P < 0.01). The average percentage decreases in CL/F and V/F were 49.0% (95% CI 31.1, 66.9) and 53.7% (95% CI 40.1, 67.4), respectively (P < 0.01). CONCLUSIONS: SchE can increase the oral bioavailability of tacrolimus. The results of this study will add important information to the interaction area between drugs and herbal products.     

Single- and multiple-dose pharmacokinetics of bosentan and its interaction with ketoconazole

AIMS: The present study was conducted to characterize the single- and multiple-dose pharmacokinetics of bosentan, a dual endothelin receptor antagonist, and to investigate a possible pharmacokinetic interaction with ketoconazole. METHODS: In a randomized, two-way crossover study, 10 healthy male subjects received treatments A and B. Treatment A consisted of a single dose of 62.5 mg bosentan on day 1 followed by 62.5 mg twice daily for 5.5 days. Treatment B consisted of bosentan (62.5 mg twice daily) for 5.5 days plus concomitant ketoconazole (200 mg once daily) for 6 days. Plasma concentrations of bosentan and its three metabolites were measured on days 1 and 7 of treatment A and on day 6 of treatment B. RESULTS: Bosentan was absorbed and eliminated with a tmax of 4.5 h (range 3.5-6.0 h) and a t(1/2) of 5.4 h (95% CI; 4.5, 6.6). Upon multiple dosing, the exposure to bosentan was reduced by 33% without change in tmax and t(1/2). Concomitant administration of ketoconazole increased the Cmax and AUC of bosentan 2.1- (95% CI; 1.5, 2.7) and 2.3-fold (95% CI; 1.8, 2.9), respectively. Exposure to the metabolites was low and represented less than 25% of that to bosentan both after single and multiple doses. In the presence of ketoconazole, formation of the metabolites was inhibited. DISCUSSION: The multiple-dose pharmacokinetics of bosentan are consistent with the phenomenon of auto-induction. In the presence of CYP3A4 inhibitors, bosentan concentrations may be increased 2-fold.