Evaluation of the Intestinal Absorption of Erythromycin in Man: Absolute Bioavailability and Comparison with Enteric Coated Erythromycin

To determine the role of acid hydrolysis on the gastrointestinal absorption of erythromycin, six healthy subjects received erythromycin as a 240 mg intravenous dose, a 250 mg oral solution administered via endoscope directly into the duodenum and bypassing the stomach, and an enteric-coated 250 mg capsule. Blood samples were collected for 6 hours and serum erythromycin quantified by a microbiological method. The time to achieve maximum serum concentrations for the solution was 0.25 ± 0.08 (mean ± SD) hours and for the capsule was 2.92 ± 0.55 hours. The absolute bioavailability of erythromycin from the capsule was 32 ± 7% and for the duodenal solution 43 ± 14%. The ratio of the areas under the serum erythromycin concentration-time curve of capsule to solution was 80 ± 28% (range 38 to 110%). There is substantial loss of erythromycin apart from gastric acid hydrolysis, which cannot be accounted for by hepatic first-pass metabolism. Attempts to further improve the oral bioavailability of erythromycin beyond 50% by manipulation of formulation are likely to be futile.     

Bioavailability and Pharmacokinetics in Man of Orally Administered Theophylline

Abstract The pharmacokinetics of theophylline after both intravenous and oral administration was investigated in six hospitalized patients with normal renal, hepatic and pulmonary functions. A rather wide range of biological half-lives from about 3–16 hours and plasma clearance values of about 16.5–115 ml kg^-1 hr^-1 were found in the investigated patients, who were from 31 to 73 years of age. The apparent volumes of distribution during the eliminatory β-phase (V_dβ) were within the range 0.394–0.616 1 kg^-1 with a mean value of 0.484 1 kg^-1 ±0.082 S.D., as determined from the intravenous data, and in excellent agreement with the value obtained from the peroral data. Except in one case theophylline exhibited two compartment characteristics after intravenous administration, while the oral data in only one patient showed this pharmacokinetic configuration and had to be analysed according to one-compartment characteristics in the other five subjects. In the oral experiments absorption rate constants of from about 0.57 to 2.17 hr^-1 were found for the administered microparticulate theohylline tablet preparation, Nuelin® from Riker Laboratories. A wide range of lag-times from 0 to 1.32 hours were also demonstrated in the experiments. The systemic availability of theophylline in this preparation varied from 82.8 to 103% as determined on basis of the ratios of areas under the oral and intravenous serum concentration curves. It is conclusively stated that therapeutic plasma concentrations of theophylline probably may be maintained and controlled efficiently with the investigated oral theophylline preparation. Because of the interindividual variability in the biological half-life of the compound monitoring of the serum theophylline concentration is generally advised in order to avoid toxic side effects, in particular in relation to the initial establishment of a therapeutic serum concentration level in the individual subjects to be treated.     

Absolute Bioavailability and Absorption Profile of Cyanamide in Man

A pharmacokinetic study of cyanamide, an inhibitor of aldehyde dehydrogenase (EC1.2.1.3) used as an adjuvant in the aversive therapy of chronic alcoholism, has been carried out in healthy male volunteers following intravenous and oral administration. Cyanamide plasma levels were determined by a sensitive HPLC assay, specific for cyanamide. After intravenous administration cyanamide displayed a disposition profile according to a two-compartmental open model. Elimination half-life and total plasma clearance values ranged from 42.2 to 61.3 min and from 0.0123 to 0.0190 L · kg ^–1 · min^–1, respectively. After oral administration of 0.3, 1.0, and 1.5 mg/kg ± SEM values of C_max, t_max (median) and AUC were 0.18 ± 0.03, 0.91 ± 0.11, and 1.65 ± 0.27 g · ml ^–1 ; 13.5, 13.5, and 12 min; and 8.59 ± 1.32, 45.39 ± 1.62, and 77.86 ± 17.49 g · ml ^–1 · min, respectively. Absorption was not complete and the oral bioavailability, 45.55 ± 9.22, 70.12 ± 4.73, and 80.78 ± 8.19% for the 0.3, 1.0, and 1.5 mg/kg doses, respectively, increased with the dose administered. The models that consider a first-order absorption process alone (whether with a fixed or variable bioavailability value as a function of dose) or with loss of drug due to presystemic metabolism (with zero-order or Michaelis–Menten kinetics) were simultaneously fitted to plasma level data obtained following 1 mg/kg iv and 0.3, 1.0, and 1.5 mg/kg oral administrations. The model that best fit the data was that with a first-order absorption process plus a loss by presystemic metabolism with Michaelis–Menten kinetics, suggesting the presence of a saturable first-pass effect.     

麦滋林-S颗粒在人体内药代动力学及生物利用度的研究

本文建立了测定麦滋林-S颗粒在人体中的血药浓度的高效液相色谱法,对7名健康志愿受试者和3名慢性胃炎患者进行了药代动力学研究,用计算机McpKp程序计算药代动力学参数并拟合了房室模型,以麦滋林-S溶液剂为对照制剂,麦滋林-S颗粒的相对生物利用度为94.12％。     

阿斯匹林肠溶缓释胶囊的人体药代动力学及生物利用度研究

本文报道口服阿斯匹林肠溶缓释胶囊及肠溶片后体内水杨酸盐的高效液相色谱测定法及正常人药代动力学和生物利用度研究的结果。12名健康志愿者，随机分为两组，分别交叉口服阿斯匹林肠溶缓释胶囊和肠溶片各600mg。阿斯匹林在体内迅速转化为活性代谢产物水杨酸，测定口服给药后不同时间血中水杨酸的浓度，使用3P87实用药代动力学程序对药一时曲线进行处理，结果表明，水杨酸在体内的代谢过程符合一室模型。单剂空腹口服阿斯匹林肠溶缓释胶囊和肠溶片后，体内水杨酸的平均峰浓度为35．52±8．28mg／L和30．32±8．96mg／L；平均达峰时间为5．70±1．25h和7．40±2．17h开均药-时曲线下面积为328.4±92．2mg／（Lh）和316．0±70．95mg／（L·h)）;消除半衰期为3．11±1．25h和3．84±1．72h；吸收迟滞时间为2．33±0．65h和3．35±1．16h。肠溶缓释胶囊的达峰时间明显短于肠溶片。缓释胶囊对片剂的相对生物利用度为103．9％。     

NONMEM法探索CYP1A2对儿童卡马西平群体药动学的影响

目的 用非线性混合效应模型法探索CYP1A2对儿童卡马西平群体药动学的影响。方法 回顾性收集180名癫痫患儿的临床资料及720个卡马西平血药浓度监测数据,采用非线性混合效应模型法估算群体药动学参数并建立模型,采用图形法和可视化预测检验的方法对最终模型进行验证。结果 建立了该药物的一级吸收一室模型,最终模型参数如下：CL=3.25×（WT/29.8）^0.22×e^{0.05（AA=1）}×e^ηCL（L·h^-1）,V_d=34.78×e^ηVd（L）,K_a=1.2·h^-1。当CYP1A2-163为AA时,AA=1;当CYP1A2-163为CA或CC时,AA=0。患儿体质量的增长可以导致药物清除率的非线性增加,CYP1A2-163C>A突变可加快卡马西平的清除。结论 患儿的体质量与CYP1A2基因突变（-163C>A）对CL有显著影响,在用药前建议考虑患者体质量与CYP1A2基因型。     

Comparison of two population pharmacokinetic programs,NONMEM and P-PHARM,for tacrolimus

OBJECTIVES: To compare the population modelling programs NONMEM and P-PHARM during investigation of the pharmacokinetics of tacrolimus in paediatric liver-transplant recipients. METHODS: Population pharmacokinetic analysis was performed using NONMEM and P-PHARM on retrospective data from 35 paediatric liver-transplant patients receiving tacrolimus therapy. The same data were presented to both programs. Maximum likelihood estimates were sought for apparent clearance (CL/F) and apparent volume of distribution (V/F). Covariates screened for influence on these parameters were weight, age, gender, post-operative day, days of tacrolimus therapy, transplant type, biliary reconstructive procedure, liver function tests, creatinine clearance, haematocrit, corticosteroid dose, and potential interacting drugs. RESULTS: A satisfactory model was developed in both programs with a single categorical covariate--transplant type--providing stable parameter estimates and small, normally distributed (weighted) residuals. In NONMEM, the continuous covariates--age and liver function tests--improved modelling further. Mean parameter estimates were CL/F (whole liver) = 16.3 l/h, CL/F (cut-down liver) = 8.5 l/h and V/F = 565 l in NONMEM, and CL/F = 8.3 l/h and V/F = 155 l in P-PHARM. Individual Bayesian parameter estimates were CL/F (whole liver) = 17.9 +/- 8.8 l/h, CL/F (cut-down liver) = 11.6 +/- 8.8 l/h and V/F = 712 +/- 792 l in NONMEM, and CL/F (whole liver) = 12.8 +/- 3.5 l/h, CL/F (cut-down liver) = 8.2 +/- 3.4 l/h and V/F = 221 +/- 164 l in P-PHARM. Marked interindividual kinetic variability (38-108%) and residual random error (approximately 3 ng/ml) were observed. P-PHARM was more user friendly and readily provided informative graphical presentation of results. NONMEM allowed a wider choice of errors for statistical modelling and coped better with complex covariate data sets. CONCLUSION: Results from parametric modelling programs can vary due to different algorithms employed to estimate parameters, alternative methods of covariate analysis and variations and limitations in the software itself.     

Assessment and Prediction of the Cutaneous Bioavailability of Topical Terbinafine,In Vivo,in Man

Pharmaceutical Research -     

Bioavailability and Related Pharmacokinetics in Man of Orally Administered L-5-Hydroxytryptophan in Steady State

Abstract The bioavailability of orally administered L-5-hydroxytryptophan in steady state was investigated at four increasing multiple dose levels in five patients suffering from various myoclonic disorders. An L-aromatic amino acid decarboxylase inhibitor was co-administered in all the experiments. The disposition pharmacokinetics of the amino acid had been established in the same patients in preceding intravenous single dose experiments. The finding of a direct proportionality between the size of the oral dose level of L-5-hydroxytryptophan and the corresponding areas under the plasma concentration curves within a dosage interval at steady state strongly indicates dose independent, linear pharmacokinetics of the compound. The systemic availability of L-5-hydroxytryptophan exhibited an interindividual range of 47–84%, with a mean value of 69.2% ±4.7 S.E.M. The absorption took place at a rather slow rate as judged from times of 1.8 to 3.3 hours elapsing from administration of the compound until occurance of the maximum measured plasma concentrations. Transitory nausea and vomiting were only recognized in few instances during the gradual building up of increasing steady state levels of L-5-hydroxytryptophan in the patients, and the importance of a slow initiation of therapeutical treatment with the amino acid is emphasized.     

吲哚拉新控释片及其胶囊的生物利用度比较

本文比较了吲哚拉新控释片和普通胶囊在人体内生物利用度,吲哚拉新血浆浓度用高效液相色谱法（HPLC）测定。结果表明,在6名受试者中．两种制剂的吸收程及基本一致;但控释片的峰药浓度（Cmax）显著低于普通胶囊（P＜0.01）,其达峰时间（Tmax）也明显延迟（P＜0.01）。给予单剂量（250mg）控释片后．在给药后4h至24h其血浆浓度显著高于普通胶囊（P＜0．05）。说明该控释片可避免普通制剂初期的高峰血药浓度,从而降低副作用并延长了给药间隔时间。     

A Comparison of the Pulmonary Bioavailability of Powder and Liquid Aerosol Formulations of Salmon Calcitonin

PURPOSE: To compare the pulmonary pharmacokinetics and relative bioavailability of salmon calcitonin delivered as aqueous droplets, pH 6.6 and pH 4.8 with that of a spray dried powder in healthy volunteers. METHODS: Spray dried powders (1.6 microm [GSD 2.1]) containing 5% by wt. sCal, 6.25% human serum albumin, 73.55% mannitol and 15% citric acid/sodium citrate were prepared using a Buchi model 190 spray drier. Aqueous solutions were prepared by dissolving the spray dried powder at a sCal concentration of 1.25 mg/ml, pH was adjusted using 21 mM sodium hydroxide. Aerosols were delivered as part of a 4 way cross-over study to 16 healthy volunteers. The Nektar pulmonary delivery device was used to deliver the dry powder aerosol. A Salter nebulizer controlled by a Rosenthal dosimeter was used to deliver the aqueous aerosols. Miacalcin injection was used as the subcutaneous control. Dose delivered to the lung was estimated by gamma scintigraphy. Plasma concentrations of sCal were measured using a radioimmunoassay. RESULTS: Aerosol size distributions were matched, 3.3 microm MMAD and approximately 2.2 GSD. Inhaled flow rates were similar, although not equal, 5.8 and approximately 9.8 l/min respectively for dry powder and liquid inhalations. Lung doses of sCal ranged from 53 to 88 microgm, peripheral lung doses from 25 to 51 microgm. Pharmacokinetic profiles and lung bioavailability relative to subcutaneous injection for all formulations were similar (not statistically significantly different p > 0.05), relative lung bioavailability ranged from 11% to 18%, estimates of relative bioavailability based on peripheral lung dose ranged from 20% to 33%. CONCLUSION: The study showed no difference in pharmacokinetic profiles between the various aerosol dosage forms. pH of the aqueous solutions did not affect kinetics or relative bioavailability.     

Absorption and Bioavailability of Diclofenac after Rectal Administration of Diclofenac-Na Gel Preparation in Rat and Man

In order to evaluate diclofenac-Na (DC-Na) micro-enema, DC-Na gel preparations were administered to rats and man. When DC-Na gel preparations were rectally administered at various pH (pH 5– 8) to rats, their bioavailability increased at higher pH. The bioavailability of DC-Na gel preparations (pH 8.0) in rats was significantly higher than that with conventional suppository bases, Witepsol H-15 and polyethylene glycol 1000 (PEG 1000). In man, the DC-Na gel preparation showed higher C_max and higher bioavailability than commercial suppository made with an oily base. DC-Na gel preparations containing 10% v/v oleic acid showed a prolonged action. The irritative effect of DC-Na gel preparation on rectal mucosa in rats was weaker than that of PEG 1000, but similar to that of Witepsol H-15. Therefore, the present results suggest that gel preparation is a favorable form for rectal administration of diclofenac-Na.     

利用前药设计提高药物生物利用度的研究进展

前药设计是提高药物吸收的有效途径之一.本文综述了近几年通过前药设计提高药物生物利用度的研究进展,主要分为水溶性前药研究与脂溶性前药研究.水溶性前药的目的在于提高药物在水中的溶解度,这些前药载体包括磷酸类、氨摹酸类和其它类.而脂溶性前药的目的在于提高药物的渗透性,这类前药主要以酯类载体为主.     

Use of the Stable Isotopes Technique to Evaluate the Bioavailability of a Pharmaceutical Form of Magnesium in Man

Pharmaceutical Research -     

Estimation of Oral Bioavailability of a Long Half-Life Drug in Healthy Subjects

Purpose. To estimate and compare the oral bioavailability of a drug (BMS-187745) administered as single doses of oral solution of either the parent drug or its prodrug (BMS-188494). Methods. A single-dose, two-period, three-treatment, control-balanced, residual-effect, incomplete block crossover study was completed in 16 healthy male subjects. All subjects received a 10 mg IV infusion of BMS-187745, and a single oral dose of either BMS-187745 (PO1) or BMS-188494 (PO2). A model is proposed to calculate the oral bioavailability of BMS-187745 which has a long half-life; incomplete data points were available to characterize its elimination phase. The plasma concentration-time data obtained following IV infusion of parent drug, and after administration of either PO1 or PO2 treatment were fitted simultaneously with systemic pharmacokinetic parameters shared by both the oral and IV routes of administration. Results. The best simultaneous fittings of the plasma concentration-time data were obtained by using a biexponential pharmacokinetic model with a first-order absorption rate constant. The mean bioavailability (F) values of BMS-187745 estimated by the proposed model were 26.5% and 2.6% when given as oral solution of its prodrug and as the parent drug. The coefficient of variation (CV) of these F values are reasonable, ranging from 38–40%. In contrast, F calculated by the model-independent AUC method exhibited high CV, ranging from 111–120%. Conclusions. The oral bioavailability values estimated by the proposed model were more reasonable compared to those calculated by the model-independent AUC method. The proposed approach may be useful for estimating bioavailability of long half-life drugs when incomplete data points are available to characterize their elimination phase.     

Assessing Topical Bioavailability and Bioequivalence: A Comparison of the In vitro Permeation Test and the Vasoconstrictor Assay

Purpose

To compare the sensitivity of a pharmacokinetic assay, the in vitro permeation test (IVPT), with that of a pharmacodynamic assay, the human skin blanching or vasoconstrictor (VC) assay, in assessing the relative bioavailability of topical clobetasol propionate products.

Methods

The percutaneous absorption of clobetasol propionate from five commercial products was measured in vitro using cryopreserved human skin. The pharmacodynamic potency of the same five products was also assessed in vivo using the VC assay, the surrogate method by which regulatory authorities in the United States establish the bioequivalence of generic topical glucocorticoid products.

Results

IVPT found total clobetasol absorption varying ten-fold from highest to lowest product, whereas the VC assay found this same difference was less than two-fold. The coefficient of variation ranged from 78 to 126% in the VC assay, but only 30–43% for IVPT. Statistically, IVPT could separate the 5 products into three groups: 1) ointment, 2) cream and gel, 3) emollient cream and solution). Due to its greater variability as well as saturation of the pharmacodynamic response at higher flux levels, the VC assay found all products except the solution to be equipotent.

Conclusions

IVPT was found to be substantially more sensitive and less variable than the VC assay for assessing clobetasol bioavailability.     

美欧卡霉素三种口服制剂的相对生物利用度比较

用微生物法测定血药浓度。本文报道6名健康志愿者口服美欧卡霉素干糖浆、片剂及胶囊后的生物利用度比较结果。口服1g上述三种剂型后,其相对生物利用度分别为100%、121%及100%。各主要参数三种剂型间也无显著差异。     

Experiences in the application of NONMEM to pharmacokinetic data analysis

Ethical issues arising from the use of patients in medical research have stimulated pharmacokinetic research in population kinetics, which requires only a few concentration samples of each individual. Using historical maprotiline data, the new approach of population kinetics was investigated and compared to individually estimated kinetics. Two different population kinetic methods were applied. The naive approach, a quick and dirty method, was compared to the nonlinear mixed-effects method, which was applied by the NONMEM package. Based on the results we obtained from actual maprotiline data as well as from simulated data, NONMEM is a reasonable tool for the estimation of population pharmacokinetic parameters. The main advantage of NONMEM over the naive approach lies in the possibility of obtaining standard deviations of random effects related to the variability between subjects.     

Estimation of Bioavailability on a Single Occasion After Semisimultaneous Drug Administration

A method for determination of absorption rate and bioavailability was developed to reduce the influence of intraindividual variability and applied to the absolute intraperitoneal availability of lithium in the rat. In this method the test and the reference doses are given with a few hours' interval, and the resulting concentration–time data are analyzed by nonlinear regression. The bioavailability estimation by this approach was compared to that of the traditional method, with test and reference doses given on separate days. The mean estimates of availability were 1.035 ± 0.109 (N = 7) and 0.984 ± 0.052 (N = 11) for the traditional and the alternative method, respectively. Thus, the precision was better in the latter. Major influences of dose- or time-dependent kinetics of lithium on the availability estimates were excluded by the design used. The estimation of bioavailability was robust with respect to the choice of absorption and disposition model and the duration of sampling. The plasma clearance of lithium was 169 ± 15 ml/hr/kg, with a terminal half-life of 5.0 ± 0.5 hr (N = 5).     

A Comparison of Multiple Testing Procedures for the Gold Standard Non-Inferiority Trial

For the three-arm parallel-group design, several procedures have been proposed in the literature to control for the multiple type I error when all groups are to be statistically compared. Mere statements regarding the rejection of the null hypotheses are not satisfactory, but instead confidence intervals are more desirable. For this purpose, the procedure by Koch and Röhmel (2004 Koch , A. , Röhmel , J. ( 2004 ). Hypothesis testing in the “gold standard” design for proving the efficacy of an experimental treatment relative to placebo and a reference . J. Biopharm. Stat. 14 : 315 – 325 .[Taylor &; Francis Online] , [Google Scholar]) is modified and the theoretical reasoning behind it is given. However, one combination of effects occurs where control of the multiple type I error cannot be guaranteed. This pathologic case is discussed theoretically and further investigated in a simulation study.