An application of population kinetics analysis to estimate pharmacokinetic parameters of sodium tungstate after multiple-dose during preclinical studies in rats

The purpose of this study was to use a population approach in the preclinical development program of sodium tungstate in the rat in order i) to compute individual pharmacokinetic parameters of this compound after repeated oral administrations, until the 4-week toxicology study, using an empirical Bayes methodology; and ii) to study the influence of the administered dose, of the gender and of the duration of treatment on the pharmacokinetic parameters. Four studies were used representing a mixture of single intravenous administration and multiple oral administrations. The treatment duration ranged from 7 to 28 days. Intravenous dose was 9 mg/kg; three different oral doses were tested, 50, 100 and 200 mg/kg/day. Plasma concentration profiles versus time were compatible with a two-compartment model. A significant gender effect was found on bioavailability. The duration of treatment and the administered dose did not significantly explain part of the interindividual variability of pharmacokinetic parameters. The absorption of tungsten was rapid (1-3 hr). Total plasma clearance and elimination half-life averaged 2.8 ml/min/kg and 3.04 hr in males, and 3 ml/min/kg and 2.74 hr in females. The bioavailability was on an average 70%; being significantly higher in females than in males (0.78 versus 0.61). This compartmental approach should be considered as complementary to the usual non-compartmental approach used for analysis of preclinical data and should be a valuable tool to characterise the pharacokinetic/pharmacodynamic behaviour of a drug.     

<Emphasis Type="Italic">In Vitro/in Vivo</Emphasis> relationship of gabapentin from a sustained-release tablet formulation: A pharmacokinetic study in the beagle dog

The aim of this study was to examine the in vitro/in vivo relationship of the drug release behavior of a sustained-release formulation of gabapentin. The immediate-release formulation was used as the reference formulation. The dissolution test was employed using pH 1.2, 4.0, or 6.8 buffer solution, or water, to determine the in vitro release behaviors of gabapentin tablets. Gabapentin was released completely within 1 h from the immediate-release tablet and released for 12 h from the sustained-release tablet. A single dose (600 mg) of each formulation was orally administered to four beagle dogs under fasted conditions, and the pharmacokinetic parameters were calculated. Although the sustained-release tablet did not disintegrate and had slow drug release characteristics, it showed similar pharmacokinetic parameters to the immediate-release tablet, which rapidly disintegrated and showed fast drug release. Thus, the in vivo release of gabapentin did not correlate with in vitro release of drug.     

New perspectives in bio-analytical techniques for preclinical characterization of a drug candidate: UPLC-MS/MS in in vitro metabolism and pharmacokinetic studies

Lead optimization requires rapid bio-analytical turnover for the generation of early absorption, distribution, metabolism, excretion (ADME) and pharmacokinetics (PK) data maintaining a high quality level. Therefore, one of the major challenges in the bio-analytical field is to achieve faster and more sensitive quantification protocols. In the present communication, a comparison between HPLC and ultra performance liquid chromatography (UPLC) performances in terms of sensitivity and resolution is shown using a pharmakokinetic study and a metabolism study as models. The studies highlight the features of the new technology and the resulting impact in the PK throughput and in the characterization of isomeric metabolites using UPLC/MS/MS technique.     

A 6-month dietary toxicity study of acidic sodium aluminium phosphate in beagle dogs

Sodium aluminium phosphate [NaAl3H14(PO4)8. 4H2O], a leavening acid, was administered to groups of six male and six female beagle dogs at dietary concentrations of 0, 0.3, 1.0 or 3.0% for 6 months. No adverse treatment-related clinical signs were observed. There were no statistically significant differences in mean body weights between test and control groups at any of the weekly determinations. Weekly mean food consumption values of all male treated groups did not differ significantly from those of the control group at any stage of the study. Statistically significant reductions in food consumption occurred sporadically in all treated groups of female dogs. No significant absolute or relative organ-weight differences were found between any of the treated groups and their respective controls. Haematological, blood chemistry and urinalysis data showed no toxicologically significant trends. Histopathological examination revealed no changes considered to be related to treatment. Thus dietary administration of sodium aluminum phosphate for 6 months at concentrations of 3% or lower caused no significant toxicological effects in beagle dogs.     

A longitudinal study assessing lens thickness changes in the eye of the growing beagle using ultrasound scanning: relevance to age of dogs in regulatory toxicology studies

The lens is formed in utero with new secondary lens fibres added as outer layers throughout life in a growth pattern characteristic of the species. This study examined the time course of beagle lens growth to better understand the optimal starting age of dogs for safety studies to support adult versus paediatric indications, and to assess the feasibility of non‐invasively monitoring lens growth with high frequency ultrasound. Ultrasound scanning was performed in six female beagle dogs using the Vevo770. All dogs were imaged in B‐mode using local anaesthetic but without sedation. Imaging was carried out every 2 weeks from 8 to 22 weeks of age and then monthly until 62 weeks of age. The dogs tolerated the procedure well. The lens was visible in all dogs and measuring the lens thickness with high frequency ultrasound demonstrated good analytical reproducibility [Root Mean Square (RMS) = 3.13%]. No differences between the left and right eye existed and lens thickness correlated with body weight. The highest weekly growth rate was before 12 weeks of age. A statistically significant difference between monthly thickness was detected until 42 weeks of age at which point growth reached a plateau. During the experiment, lenses grew by 29.7% reaching an average thickness of 6.4 mm ± 0.03. By 10 months of age (the typical age used for routine toxicological evaluation), beagles have reached a plateau in lens growth that is analogous to human adults. Where lens is a target organ of concern it is suggested that beagles under 6 months old may be a better model for determining paediatric safety. Copyright © 2014 John Wiley & Sons, Ltd.     

Estimation and inference in pharmacokinetic models: The effectiveness of model reformulation and resampling methods for functions of parameters

It is well known that high parameter estimate correlations and asymptotic variance estimates can cause estimation and inference problems in the analysis of pharmacokinetic models. In this paper we show that analysis of three important functions of pharmacokinetic parameters, the half-life, mean residence time, and the area under the curve, can sometimes be greatly improved by reformulating the model to address collinearity and by using the bootstrap to form confidence intervals. The resultant estimators can be more accurate than the original ones, and resultant confidence intervals can be narrower. Of the three measures, the half-life estimator is much better behaved than the estimators of mean residence time and area under the curve under collinearity, suggesting that it (or measures like it) should be used more often.     

9-[2-(膦酰甲氧基)乙基]腺嘌呤一钠盐在比格犬体内的毒代动力学和毒理学研究

目的为9-[2-(膦酰甲氧基)乙基]腺嘌呤一钠盐(PMEA-Na)重复给药的毒性研究提供毒代动力学资料。方法采用液相色谱质谱联用方法测定样品中的药物浓度,数据经统计矩方法处理得到毒代动力学参数,并完成血清生化学及组织病理学检测。结果比格(Beagle)犬静脉单次及多次给药(14 d,每日1次)后,在给药剂量范围内, AUC均表现为剂量依赖性。在1.0, 3.0与6.0 mg·kg-1PMEA-Na时,AUC分别为(2.3±0.5),(8.4±1.6),(17.5±3.7)mg·L-1·h(单剂量)和(5.0±0.4),(15.9±3.2),(30.3±4.7) mg·L-1·h(多剂量)。PMEA-Na主要经肾脏排出体外,且给药14 d后肾功能受损药物排泄能力降低。与对照组比较, 6.0 mg·kg-1组血清生化学检测指标丙氨酸氨基转换酶、总胆红素、尿素氮、肌酐及甘油三酯均升高,葡萄糖水平下降。6.0 mg·kg-1组的组织病理学检查发现肝脏和肾脏有明显的病理形态学改变。结论比格犬经静脉多次给PMEA-Na 14 d后出现毒性反应,毒性靶器官主要为肾脏和肝脏。     

9-［2-(膦酰甲氧基)乙基］腺嘌呤一钠盐在比格犬体内的毒代动力学和毒理学研究

目的 为9-［2-(膦酰甲氧基)乙基］腺嘌呤一钠盐（PMEA-Na）重复给药的毒性研究提供毒代动力学资料。方法 采用液相色谱质谱联用方法测定样品中的药物浓度，数据经统计矩方法处理得到毒代动力学参数，并完成血清生化学及组织病理学检测。结果 比格(Beagle)犬静脉单次及多次给药（14 d，每日1次）后，在给药剂量范围内，AUC均表现为剂量依赖性。在1.0, 3.0 与6.0 mg·kg^-1 PMEA-Na时，AUC分别为（2.3±0.5），（8.4±1.6），（17.5±3.7）mg·L^-1·h(单剂量)和（5.0±0.4），（15.9±3.2），(30.3±4.7) mg·L^-1·h（多剂量）。PMEA-Na主要经肾脏排出体外，且给药14 d后肾功能受损药物排泄能力降低。与对照组比较, 6.0 mg·kg^-1组血清生化学检测指标丙氨酸氨基转换酶、总胆红素、尿素氮、肌酐及甘油三酯均升高, 葡萄糖水平下降。6.0 mg·kg^-1组的组织病理学检查发现肝脏和肾脏有明显的病理形态学改变。结论 比格犬经静脉多次给PMEA-Na 14 d后出现毒性反应，毒性靶器官主要为肾脏和肝脏。     

A biopharmaceutic approach in designing a controlled release tablet of sodium monofluorophosphate: 1. in vitro and in vivo studies in beagle dogs

The purpose of this study was to develop a controlled release tablet (CRT) of sodium monofluorophosphate (NaMFP) based on biopharmaceutic and pharmacokinetic principles. NaMFP was introduced in the early eighties to treat osteoporosis. The required dose size (200 mg of NaMFP) and time of drug delivery (8.3 h) were theoretically determined based on the pharmacokinetic parameters of fluoride (F^?). A CRT was formulated with ethyl cellulose (EC) by the direct compression method. The ratio of drug to polymer was adjusted 1:1, after studying the in vitro release profiles. The release mechanism from the developed dosage form followed the square root of time relationship. This dosage form was evaluated for its in vivo performance in dogs. The pharmacokinetics of F^?, after the IV and PO administration of NaMFP, was determined to standardize the animal model. F^? followed a two-compartment model and no significant differences were found between the two routes of administration. The bioavailability in dogs was only 60%. The reason for this poor bioavailability was postulated to be the delivery of drug extended beyond the principal sites of absorption of the gastrointestinal tract. Hence, we decided to characterize the absorption sites of NaMFP and to modify the CRT.     

Repeated analysis of semen parameters in beagle dogs during a 2-year study with the HMG-CoA reductase inhibitor, atorvastatin.

Sperm analyses are often incorporated into reproductive toxicity studies in rats. Due to the relative ease of collecting multiple samples throughout a study, semen analysis in non-rodents such as dogs offers the opportunity to assess potential development of functional effects of compounds on male reproduction over time. In the present study, semen parameters were evaluated in beagle dogs during and at termination of a chronic toxicity study with the 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitor, atorvastatin. Male dogs received 0, 10, 40, or 120 mg/kg orally in gelatin capsules for up to 104 weeks (n = 10/group). After 52 weeks of dosing, 3 dogs/group were euthanized, and 2/group were withdrawn from treatment for a 12-week reversal period and euthanized at Week 64. The remaining 5/group continued treatment until Week 104. Semen was collected from all animals for 3 consecutive weeks prior to termination of the 52-week animals (Weeks 50, 51, 52) for analysis of sperm parameters, using manual methods of evaluation. Semen was collected from the remaining animals at Weeks 64, 78, 91, and 104, and was analyzed. At necropsy, testes, epididymides, and prostates were weighed and evaluated histologically, and epididymal sperm counts were determined. Serum cholesterol was decreased 25--60% at all doses during the study. There were no drug-related differences in semen volume and color, total sperm count, and sperm concentration, morphology, progressiveness, and percent motility during treatment with atorvastatin. There were also no effects on reproductive organ weights or histopathology, and no effects on epididymal sperm count. Thus, incorporation of semen analyses into this study allowed the evaluation of potential male reproductive effects in dogs at multiple time points during the study. Statistical power calculations demonstrated acceptable statistical power (> 80%) for semen sperm count, concentration, morphology, and motility with group sizes of 8--10 animals, and for semen sperm count and concentration or epididymal sperm count with group sizes of 3--5 animals, using the methodology described in this paper.     

Accuracy of repeated blood sampling in rats: a new technique applied in pharmacokinetic/pharmacodynamic studies of the interaction between warfarin and co-enzyme Q10

In the past, combined pharmacokinetic/pharmacodynamic (PK/PD) modeling studies of oral anticoagulants in rats have been hampered by the technical problems of blood sampling. In the present study, a semi-micromethod of preparing serial plasma samples for accurate assessment of the prothrombin times (PT) and clotting factor VII activity (CFA) in rats is proposed. The method consists of orbital bleeding, blood sample weighing, gravity calculation and buffer volume adjustment. No significant differences of CFA (percentage normal) were found between citrate-diluted and undiluted plasma. This technique was employed to examine the possibility of PK/PD interaction between warfarin and Co-enzyme Q₁₀ (CoQ₁₀). Rats were given a single oral dose (1.5 mg/kg) of warfarin either alone or on day 4 of an 8-day oral dosing regimen of 10 mg/kg CoQ₁₀ daily. Serial plasma and serum samples, which were subjected to respectively measurements of the anticoagulant effects and concentrations of warfarin and its main metabolites, were obtained over a 96-h period following warfarin administration. All rats survived the whole experiment and maintained a stable condition except for a marked hematocrit decrease. CoQ₁₀ significantly augmented warfarin metabolism but showed little effect on the absorption of warfarin. CoQ₁₀ alone had no apparent effect on either the PT or CFA. The concomitant administration of CoQ₁₀ and warfarin does not significantly affect the anticoagulant effect of warfarin. In conclusion, the proposed serial orbital bleeding technique in rats to prepare an accurate citrate-diluted plasma for PT and CFA measurement is rapid and reliable.