Determination of dextromethorphan metabolizer phenotype in healthy volunteers

Summary The dextromethorphan metabolizer phenotype in 450 healthy volunteers (299 men, 151 women) was determined after oral administration of a 15 mg dose. In 8 h-postdose urine samples the ratio of dextrorphan (DOP) to dextromethorphan (DMP) was measured by HPLC.Urinary excretion of DMP and DOP within 8 h after the dose varied greatly between individuals, ranging from 0–11% and 0.04–100% of dose, respectively. In 143 test subjects the fraction of the dose of DMP in urine was below the detection limit. In the remaining 307 volunteers the metabolic ratio (MR) of DOP to DMP varied from 0.07 to 2906. In 404 test subjects the MR was >10 and they were classified as extensive metabolizers (90% of the entire group). Of the entire group 5% had MRs of 1–10 and <1, respectively. Depending on the limit for classification of poor metabolizers, their frequency was 5–10% in the Caucasian population studied.The present data are in agreement with previous findings that the oxidative metabolic polymorphisms of debrisoquin and DMP co-segregate; the frequency of the PM phenotype of dextromethorphan in Caucasian populations varies between 5 and 10%.     

氢溴酸右美沙芬片健康人体生物等效性

目的 :研究氢溴酸右美沙芬片在健康人体的药动学及相对生物利用度。方法 :8名健康受试者单剂量随机交叉口服氢溴酸右美沙芬片参比制剂和被试制剂 6 0mg ,采用HPLC法测定用药后不同时间的血药浓度。结果 :2种制剂的体内过程均符合一房室开放模型 ,参比制剂和被试制剂的tmax分别为 (2 72± 0 2 1)h和 (2 74± 0 19)h ,cmax分别为 (5 5 1± 0 4 4) μg·L-1和(5 5 8± 0 2 7) μg·L-1,AUC分别为 (4 5 3± 2 9) μg·h·L-1和 (4 5 7± 3 0 ) μg·h·L-1,被试制剂的相对生物利用度为 (10 1±5 9) %。结论 :2种制剂具有生物等效性。     

Effect of multiple doses of montelukast, a CysLT1 receptor antagonist, on digoxin pharmacokinetics in healthy volunteers.

The effect of multiple oral doses of montelukast, a cysLT1 receptor antagonist, on the pharmacokinetics of oral digoxin was studied in healthy male volunteers in a randomized double-blind two-period crossover study. Subjects received 10 mg of montelukast or placebo daily for 11 days. On day 7, they received a single 0.5 mg oral dose of digoxin elixir. The pharmacokinetic parameters of digoxin (AUC0-->24' AUC0-->infinity' Cmax' tmax' t1/2) and cumulative urinary excretion over 120 hours were not affected by the multiple doses of montelukast. The 90% confidence interval for each of these parameters fell within prespecified clinically acceptable bounds. Side effects were mild and transient. This suggests that concurrent administration of montelukast and digoxin was well tolerated. Concurrent treatment with montelukast has no effect on the pharmacokinetics of digoxin.     

氢溴酸右美沙芬口服液在正常人体内的生物利用度

氢溴酸右美沙芬剂量小,体内代谢迅速而广泛,母体药物浓度测定困难。本文通过测定氢溴酸右美沙芬的主要活性代谢物——去甲右美沙芬的血药浓度,进而对氢溴酸右美沙芬口服液在正常人体内的生物利用度进行研究。结果表明,8例正常人口服氢溴酸右美沙芬30mg 后,在体内可迅速转化为去甲右美沙芬,约在2h 达高峰浓度,T_(1/2)在1.7～4.7h。口服液的Tmax 较片剂明显提前,统计学t 检验有显著性差异(P<0.05);但Cmax 和AUC 在两种剂型间基本一致。     

Effect of multiple doses of fimasartan, an angiotensin II receptor antagonist, on the steady-state pharmacokinetics of digoxin in healthy volunteers

Fimasartan (BR-A-657) is an angiotensin II receptor antagonist, recently approved as an antihypertensive agent. Objective: This study aimed to investigate whether administration of fimasartan has an effect on the steady-state pharmacokinetics of digoxin. Methods: An open-label, two-period, two-treatment, single-sequence, crossover study was conducted in 14 healthy male volunteers. On the first day of each 7-day treatment period, subjects received a loading dose of digoxin 0.5 mg, either alone or together with fimasartan 240 mg in the morning, followed by an additional dose of digoxin 0.25 mg after 6 h. On the subsequent 6 days, digoxin 0.25 mg, either alone or with fimasartan 240 mg was administered once daily. Serial blood samples for pharmacokinetics were collected up to 24 h after the last administration in each period. Results: The geometric mean ratio and 90% confidence intervals (CI) for the Cmax,ss and AUCτ,ss of digoxin (with/without fimasartan) were 1.307 (1.123 - 1.520) and 1.087 (1.015 - 1.165), respectively. Study medications were well-tolerated without serious adverse events or clinically meaningful changes. Conclusions: Coadministration of fimasartan with digoxin does not result in clinically significant changes of digoxin pharmacokinetics at steady-state in healthy subjects.     

Antiplatelet effects of MK-852, a platelet fibrinogen receptor antagonist, in healthy volunteers

MK-852, a cyclic heptapeptide, is a potent platelet fibrinogen receptor antagonist. When administered to normal healthy male subjects by 1- and 4-hour constant rate intravenous infusions, it provides a generally well-tolerated and reversible means of inhibition of platelet function. At infusion rates of 1 microgram/kg/min for 1 hour and 0.44 microgram/kg/min for 4 hours, respectively, MK-852 extended baseline bleeding time by greater than 2.2-fold and 2.6-fold, inhibited ADP-induced platelet aggregation by 76% and 69%, and inhibited collagen-induced platelet aggregation by 65% and 67%, respectively. The pharmacokinetics of MK-852 include an elimination half-life of approximately 2 hours, total clearance of about 150 ml/min, and volume of distribution of about 18 liters. Examination of the relationship between MK-852 whole-blood concentration in vitro and inhibition of platelet aggregation showed an EC50 of about 55 ng/ml and a Hill coefficient of 1.55. The infusions were generally well tolerated, with no study drug-related changes in blood counts or biochemical profiles.     

The effect of famotidine, a new H2 receptor antagonist, on antipyrine clearance in healthy volunteers

The salivary clearance of Antipyrine (15 mg/kg p.o.) has been measured in nine healthy volunteers (5 males, 4 females) before and after 7 days treatment with Famotidine (40 mg/day at bedtime). Samples of saliva were collected twenty four hours after each dose of Antipyrine. The post-treatment sample was taken 12 hours after the last dose of Famotidine. The clearance of Antipyrine was measured by Gas-Liquid Chromatography using the simplified formula proposed by Dossing et al. (1982). After treatment with Famotidine, a slight but significant (p less than 0.01) increase of Antipyrine clearance was observed in eight out of the nine subjects, suggesting some interference of Famotidine with Antipyrine metabolism.     

Effects of lerisetron,a new 5-HT3 receptor antagonist,on ipecacuanha-induced emesis in healthy volunteers

The purpose of these studies was to evaluate the effect of lerisetron (1-phenyl-methyl-2-piperazinyl-1H-benzimidazole hydrochloride, CAS 143257-98-1, F-0930-RS2), a new 5-HT3 receptor antagonist, on ipecacuanha-induced nausea and vomiting. The ipecacuanha model of emesis has been used to test the anti-emetic activity of several different 5-HT3 antagonists and the anti-emetic doses that were effective in the ipecacuanha model have been found to correlate well with the clinically effective doses. Study 1 investigated oral doses of lerisetron from 4 mg to 40 mg. Study 2 evaluated the duration of effect of a single dose of 20 mg oral lerisetron. Study 3 evaluated intravenous doses of 18 mg and 12 mg lerisetron. In Study 1, the 40 mg dose of oral lerisetron inhibited emesis in all test subjects. The percentage of subjects who experienced an emetic episode increased as the dose of lerisetron decreased. At the lowest dose level tested five of six subjects had an emetic episode compared with four out of five in the placebo group. In Study 2, 20 mg oral lerisetron was effective up to 12 h after administration. When ipecacuanha was administered at 18 h post-dose three of seven subjects had an emetic episode and at 24 h post-dose the incidence of emesis was similar to the placebo treatment groups in the previous study. Study 3 demonstrated the effectiveness of intravenous doses of lerisetron. The 18 mg intravenous dose reduced the number of patients experiencing emetic episodes by 75% compared with placebo, doses below 12 mg i.v. were not evaluated because of the reduced efficacy of the compound at this dose level. In conclusion, lerisetron has been shown to be effective in the treatment of ipecacuanha-induced nausea and vomiting at intravenous doses of 18 mg and at oral doses of 20 mg for up to 12 hours.     

The effect of grape seed extract on the pharmacokinetics of dextromethorphan in healthy volunteers

Purpose

Grape seed extract (GSE) has been shown to inhibit the cytochrome P450 (CYP) 2D6 isoenzyme in vitro. To determine the clinical effect of GSE on CYP2D6, the pharmacokinetic interaction between GSE and the sensitive CYP2D6 probe dextromethorphan in healthy adult volunteers was examined.

Methods

In this open label, randomized, cross-over study, 30 subjects were assigned to cohort A or B. Both cohorts ingested 30 mg dextromethorphan hydrobromide on day 1 and day 10. Cohort A received 100 mg GSE capsules three times daily on days 8, 9 and 10, while cohort B started with GSE on day ?1 until day 1. After urine collection (0–8 h) on day 1 and day 10, the urinary dextromethorphan to dextrorphan metabolic ratio was determined.

Results

Among 28 evaluable subjects, an increase of the urinary metabolic ratio was observed in 16 subjects (57 %). The mean metabolic ratio (± standard deviation) before and after GSE supplementation was 0.41 (± 0.56) and 0.48 (± 0.59), respectively. This result was neither statistically (P?=?0.342) nor clinically [geometric mean ratio 1.10, 90 % CI (0.93–1.30)] significant. Further, the majority (73 %) of the included subjects did not experience any adverse events after intake of dextromethorphan or GSE.

Conclusions

Supplementation of GSE did not significantly affect the urinary dextromethorphan to dextrorphan metabolic ratio in healthy volunteers. The results of this clinical study indicate that GSE appears to be safe to combine with drugs extensively metabolized by CYP2D6, such as dextromethorphan and tamoxifen.     

Population pharmacokinetics of an angiotensin II receptor antagonist, telmisartan, in healthy volunteers and hypertensive patients

OBJECTIVE: To describe the factors affecting pharmacokinetics of telmisartan, an angiotensin II receptor antagonist, a population pharmacokinetic (PPK) model has been developed based upon the data collected from healthy volunteers and hypertensive patients. METHODS: A total of 1566 plasma samples were collected from 20 healthy volunteers and 129 hypertensive patients, together with the demographic background. The data were analyzed by the NONMEM program using two-compartment model with first-order absorption. The robustness of the obtained PPK model was validated by the bootstrapping resampling method. RESULTS: The oral clearance (CL/F) was found to be associated with age, dose and alcohol consumption, but neither related to serum creatinine nor smoking history. The volume of distribution for the central compartment was related to age and dose, and the volume of distribution for the peripheral compartment was related to body weight and gender. The absorption rate constant (Ka) and the absorption lag time were described as function of dose. The CL/F decreased with advanced age. The CL/F decreased and Ka increased with higher dose, reflecting the super-proportional increase in the plasma levels of telmisartan. The AUC and C(max) values predicted by the present PPK model were well consistent with the observed values. The means of parameter estimates obtained with 200 bootstrap replicates were within 95-111% of the final parameter estimates from the original data set. CONCLUSION: A PPK model for telmisartan developed here well described the individual variability and exposure, and robustness of the model has been validated by the bootstrapping method.     

氨酚伪麻美芬片Ⅱ在健康人体内的药动学和生物等效性

目的研究2种国产氨酚伪麻美芬片Ⅱ在健康人体内的药动学及生物等效性。方法20名健康男性受试者按2制剂双周期交叉试验设计口服受试制剂和参比制剂各2片,采用高效液相色谱-紫外法测定血浆中对乙酰氨基酚的浓度,高效液相色谱-质谱联用法测定血浆中伪麻黄碱和右啡烷的浓度,使用DAS软件计算药动学参数并进行生物等效性统计分析。结果参比制剂和受试制剂中对乙酰氨基酚的c_(max)分别为(6 600±s 1200),(7600±2100)μg·L~(-1);t_(max)分别为(1.1±0.6),(0.9±0.6)h;A4 UC_(0～16)分别为(27 900±4700),(28 700±4 400)μg·h·L~(-1);t(1/2)分别为(4.0±1.0),(4.2±1.4)h;伪麻黄碱的C_(max)分别为(213±33),(222±34)μg·L~(-1);t_(max)分别为(1.8±0.5),(1.6±0.6)h;AUC_(0～24)分别为(1 676±261),(1 659±282)μg·h·L~(-1);t_(1/2)分别为(4.6±0.5),(4.6±0.5)h;右啡烷的c_(max)分别为(7±4),(7.5±2.9)μg·L~(-1);t_(max)分别为(2.1±0.6),(1.9±0.7)h;AUC_(0～24)分别为(38±15),(39±12)μg·h·L~(-1);t_(1/2)分别为(6±3),(5.1±2.7)h。以AUC_(0～t)计算,受试制剂中对乙酰氡基酚、伪麻黄碱和右美沙芬的相对生物利用度分别为(103±8)%,(100±18)%,(109±27)%,2种制剂的主要药动学参数经统计学检验,差异无显著意义(P>0.05)。结论2种制剂具有生物等效性。     

组胺H1受体拮抗剂盐酸依匹斯汀片人体药动学与生物等效性研究

目的研究盐酸依匹斯汀片的药动学与生物利用度,并进行生物等效性评价.方法20名健康男性志愿者单剂量口服盐酸依匹斯汀试验或参比制剂各 40 mg;采用反相高效液相色谱法测定其血药浓度.结果人体药动学研究表明,口服盐酸依匹斯汀片的药-时曲线符合二室开放模型.受试制剂与参比制剂的主要药动学参数tmax分别为(2.2±0.5)和(2.0±0.4)h;Cmax分别为(66±16)和(68±13)μg/L;t1/2分别为(10.1±1.3)和(10.4±2.4)h;AUC0-36分别为(592±88)和(601±94)μg·h·L-1;相对生物利用度为(99±13)%.结论盐酸依匹斯汀片两种制剂具有生物等效性.     

Dextromethorphan: a review of N-methyl-d-aspartate receptor antagonist in the management of pain

Dextromethorphan (DM) is a noncompetitive N-methyl-d-aspartate (NMDA) receptor antagonist, which is widely used as an antitussive agent. DM also prevents neuronal damage and modulates pain sensation via noncompetitive antagonism of excitatory amino acids (EAAs). DM has been found to be useful in the treatment of pain in cancer patients and in the treatment of methotrexate-induced neurotoxicity. Clinical studies with DM in cancer patients are reviewed in this article.     

Multiple-dose pharmacokinetics, safety, and tolerability of bosentan, an endothelin receptor antagonist, in healthy male volunteers.

The multiple-dose pharmacokinetics, safety, and tolerability of oral bosentan, a selective endothelin receptor antagonist, were investigated in healthy male volunteers. In study A, an ascending-dose, double-blind, placebo-controlled trial, doses of 100, 200, 500, and 1000 mg bosentan or placebo were given once daily for 8 days as tablets (100 and 500 mg dose strength). In study B, a double-blind, placebo-controlled trial, 500 mg tablets of bosentan or placebo tablets were given once daily for 8 days with two additional single intravenous dose administrations of 250 mg bosentan 48 hours before the first and 24 hours after the last oral dose. The drug was very well tolerated. No effects on pulse rate, ECGs, or clinical laboratory tests were observed. Marginal effects on blood pressure were seen in subjects only when standing. The oral bioavailability of bosentan was 43% to 48%, with a small interindividual variability of 20%. Doses above 500 mg did not lead to significant further increases in plasma levels of bosentan. From the first to the last day of the oral treatment phase, plasma concentrations of bosentan decreased by 30% to 40% due to a 2-fold increase in plasma clearance. Absorption and plasma protein binding did not change. The 24-hour urinary excretion of 6 beta-hydroxycortisol was increased in parallel by approximately 1.7-fold, indicating induction of cytochrome P450 3A isozymes. The two metabolites of bosentan reached plasma concentrations well below those of bosentan and will most likely not contribute to the pharmacological activity.     

Functional characterization of CP-465,022, a selective, noncompetitive AMPA receptor antagonist.

The hypothesis that aberrant alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor activity contributes to epileptogenesis and neurodegeneration has prompted the search for AMPA receptor antagonists as potential therapeutics to treat these conditions. We describe the functional characterization of a novel quinazolin-4-one AMPA receptor antagonist, 3-(2-chloro-phenyl)-2-[2-(6-diethylaminomethyl-pyridin-2-yl)-vinyl]-6-fluoro-3H-quinazolin-4-one (CP-465,022). This compound inhibits AMPA receptor-mediated currents in rat cortical neurons with an IC(50) of 25 nM. Inhibition is noncompetitive with agonist concentration and is not use- or voltage-dependent. CP-465,022 is selective for AMPA over kainate and N-methyl-D-aspartate receptors. However, the compound is found to be equipotent for AMPA receptors composed of different AMPA receptor subunit combinations. This is indicated by the finding that CP-465,022 is equivalently potent for inhibition of AMPA receptor-mediated responses in different types of neurons that express different AMPA receptor subunits. Thus, CP-465,022 provides a new tool to investigate the role of AMPA receptors in physiological and pathophysiological processes.     

氨酚伪麻美芬片Ⅱ/氨麻苯美片中对乙酰氨基酚的药动学和生物等效性

目的:研究氨酚伪麻美芬片Ⅱ/氨麻苯美片中对乙酰氨基酚的人体药动学和生物等效性。方法:采用随机交叉试验设计,20名健康男性受试者分别单剂量口服氨酚伪麻美芬片Ⅱ/氨麻苯美片受试制剂和参比制剂2片,高效液相色谱法测定血浆中对乙酰氨基酚的浓度。结果:氨酚伪麻美芬片Ⅱ受试制剂和参比制剂中对乙酰氨基酚的c_(max)分别为(7.6±s 2.1)和(6.6±1.2)mg·L~(-1),t_(max)分别为(0.9±0.6)和(1.1±0.6)h,AUC_(0～16)分别为(29±4)和(28±5)mg·h·L~(-1),受试制剂中对乙酰氨基酚的相对生物利用度为(103±8)%。氨麻苯美片中c_(max)分别为(6.0±1.0)和(6.2±1.2)mg·L~(-1),t_(max)分别为(1.5±0.7)和(1.3±0.7)h,AUC_(0～16)分别为(29±6)和(29±7)mg·h·L~(-1),相对生物利用度为(99±10)%。结论:按对乙酰氨基酚测定,受试制剂与参比制剂具有生物等效性。     

Effects of the noncompetitive NMDA receptor antagonist MK-801 on classical eyeblink conditioning in mice

N-methyl-D-aspartate (NMDA) receptors are involved in synaptic plasticity and play a critical role in learning and memory. We investigated the effects of the noncompetitive NMDA receptor antagonist (+)MK-801 on classical eyeblink conditioning of mice, using various interstimulus intervals between the conditioned stimulus (CS) and unconditioned stimulus (US). A tone was used for the CS and a periorbital shock was used for the US. In the delay paradigm, in which the US coterminated with the CS or started immediately after CS offset, the effect of (+)MK-801 (0.1mg/kg, i.p.) was a slight impairment in the acquisition of the conditioned response (CR). During subsequent CS-alone trials, the responses of (+)MK-801-injected mice were extinguished as easily as those of saline-injected mice. In the trace paradigm, (+)MK-801 impaired acquisition of the CR with a trace interval of 250 ms more than it did with a trace interval of 100 ms, and more than in the delay paradigm. (+)MK-801 injected after acquisition of 250-ms trace conditioning did not impair expression or extinction of the CR. These results suggest that NMDA receptors are involved in acquisition of the CR during longer trace interval conditioning more than during shorter trace interval conditioning or delay conditioning, and that their contribution to extinction is much smaller than their contribution to acquisition in mouse eyeblink conditioning.     

Drug discrimination based on the competitive N-methyl-d-aspartate antagonist,NPC 12626

The discriminative stimulus effects of the N-methyl-d-aspartate (NMDA) antagonists 3-([+/-]-2-carboxypiperazin-4-yl)propyl-1-phosphonic acid (CPP) and phencyclidine were assessed in a drug discrimination based on the competitive NMDA antagonist 2-amino-4,5-(1,2-cyclohexyl)-7-phosphonoheptanoic acid (NPC 12626). Adult male Sprague-Dawley rats were trained to discriminate NPC 12626 from saline using a standard two-lever fixed ratio 32 schedule of food reinforcement. NPC 12626 dose-dependently substituted for the training dose (20 mg/kg IP) with an ED₅₀ of 9.5 mg/kg. The competitive NMDA antagonist CPP completely substituted for NPC 12626 (ED₅₀=1.4 mg/kg IP). The non-competitive NMDA antagonist phencyclidine, as well as pentobarbital and NMDA, failed to substitute completely for NPC 12626, even at doses of these drugs that reduced response rates. These data indicate that the discriminative stimulus properties of NPC 12626 are selective and shared by CPP but not by phencyclidine, pentobarbital or NMDA. The emerging evidence for differences in the discriminative stimulus effects of competitive NMDA antagonists and phencyclidine suggests that competitive antagonists such as NPC 12626 and CPP may not have phencyclidine-like abuse liability.