Use of Parent Drug and Metabolite Data in Bioavailability Assessment of a Novel Diltiazem HC1 Once-Daily Product

Pharmaceutical Research -     

药物代谢酶和转运体基因多态性与中国癫痫患儿服用奥卡西平的活性代谢物血药浓度关联性研究

目的 研究代谢酶和转运体基因多态性对中国癫痫患儿服用奥卡西平的活性代谢物10-羟基卡马西平(monohydroxycarbazepine,MHD)血药浓度是否有显著影响。方法 前瞻性收集年龄0~14岁服用奥卡西平达稳态的谷浓度血浆样本,酶放大免疫法测定患者MHD血药浓度,双脱氧链终止法检测患儿代谢酶基因UGT2B7 802T>C、UGT1A9 I399C>T,以及转运体基因ABCB1 3435C>T和ABCC2 1249G>A多态性,应用单因素方差分析与Fisher最小显著差检验法分析代谢酶和转运体基因多态性与奥卡西平活性代谢物血药浓度的关联性。结果 研究共收集161例癫痫患儿的谷浓度血浆样本,单因素方差分析显示,转运体基因ABCB1 3435C>T与MHD血药浓度显著相关(P<0.05)。随后进行Fisher最小显著差检验,携带ABCB1 3435C>T突变等位基因患儿的血浆MHD浓度明显高于非携带者,未见其他代谢酶和转运体基因多态性显著影响MHD血药浓度。结论 转运体基因ABCB1 3435C>T与中国癫痫患儿奥卡西平活性代谢物血药浓度存在显著关联性,对癫痫患儿给予奥卡西平时可作该位点基因多态性检测,为临床个体化给药提供参考。     

Genotype Frequencies of Selected Drug Metabolizing Enzymes and ABC Drug Transporters among Breast Cancer Patients on FAC Chemotherapy

Abstract: Polymorphic genes of drug metabolizing enzymes and transporters may influence drug response. With some exemptions, single nucleotide polymorphisms in such genes, however, are not known to be susceptibility factors for breast cancer. This study explored genotype profiles for the breast cancer patients on fluorouracil, doxorubicin and cyclophosphamide (FAC) in a Pakistani set of population and their comparison with HapMap data. Sixty‐eight female breast cancer patients were included. All received FAC chemotherapy. Relevant genotyping was done either through restriction fragment length polymorphism or pyrosequencing. The variant allele frequencies were: 5.1% for CYP2C9*2 (430C>T), 15.4% for CYP2C9*3 (1075A>C), 27.2% for CYP2C19*2 (681G>A), 33.1% for GSTA1*B (‐69C>T, ‐52G>A), 62.5% for ALDH3A1*2 (985C>G), 58.8% and 4.4% for ABCB1 (2677 G>T/A), 64.7% for ABCB1 3435 C>T, and 15.4%, 33.1% and 39.7% for ABCC2 (–24 C>T, 1249 G>A and 3972 C>T). In comparison with HapMap, this first exploration in Pakistani samples shows higher frequency of (i) CYP2C9*3 carriers (p < 0.05) than in Hispanic, Chinese, Japanese and African samples, (ii) ALDH3A1*2 carriers (p < 0.01) than Caucasian, Hispanic, Chinese, Japanese and African samples. For ABC transporters, a higher frequency of variant allele was observed in (iii) ABCB1 2677 G>T/A (p < 0.01) than Caucasian, Hispanic and African, (iv) ABCB1 3435 C>T (p < 0.05) than Chinese, Japanese and African, (v) ABCC2 1249 G>A (p < 0.01) than Hispanic, Chinese and Japanese samples. In conclusion, cyclophosphamide activation and detoxification of reactive intermediates may be altered in the Pakistani. Though carriers of CYP2C19*2 were higher than in Caucasian and Hispanics, they did not reach statistical significance (p = 0.05).     

Quantitative Assessment of the Impact of Crohn's Disease on Protein Abundance of Human Intestinal Drug-Metabolising Enzymes and Transporters

Crohn's disease affects the mucosal layer of the intestine, predominantly ileum and colon segments, with the potential to affect the expression of intestinal enzymes and transporters, and consequently, oral drug bioavailability. We carried out a quantitative proteomic analysis of inflamed and non-inflamed ileum and colon tissues from Crohn's disease patients and healthy donors. Homogenates from samples in each group were pooled and protein abundance determined by liquid chromatography–mass spectrometry (LC-MS). In inflamed Crohn's ileum, CYP3A4, CYP20A1, CYP51A1, ADH1B, ALPI, FOM1, SULT1A2, SULT1B1 and ABCB7 showed ≥10-fold reduction in abundance compared with healthy baseline. By contrast, only MGST1 showed ≥10 fold reduction in inflamed colon. Ileal UGT1A1, MGST1, MGST2, and MAOA levels increased by ≥2 fold in Crohn's patients, while only ALPI showed ≥2 fold increase in the colon. Counter-intuitively, non-inflamed ileum had a higher magnitude of fold change than inflamed tissue when compared with healthy tissue. Marked but non-uniform alterations were observed in the expression of various enzymes and transporters in ileum and colon compared with healthy samples. Modelling will allow improved understanding of the variable effects of Crohn's disease on bioavailability of orally administered drugs.     

Impact of Excipient Interactions on Drug Bioavailability from Solid Dosage Forms

Excipients are generally pharmacologically inert, but can interact with drugs in the dosage form and the physiological factors at the site of absorption to affect the bioavailability of a drug product. A general mechanistic understanding of the basis of these interactions is essential to design robust drug products. This paper focuses on drug-excipient interactions in solid dosage forms that impact drug bioavailability, the drug substance and drug product properties affected by excipients, and the impact of excipients on physiologic processes. The extent to which drug bioavailability is affected by these interactions would vary on a case-by-case basis depending upon factors such as the potency and dose of the drug, therapeutic window, site of absorption, rate limiting factor in drug absorption (e.g., permeability or solubility limited), or whether drug metabolism, efflux, complexation, or degradation at the site of absorption play a role in determining its bioavailability. Nonetheless, a mechanistic understanding of drug-excipient interactions and their impact on drug release and absorption can help develop formulations that exhibit optimum drug bioavailability.     

Effects of Drug Transporters on Volume of Distribution

Recently, drug transporters have emerged as significant modifiers of a patient’s pharmacokinetics. In cases where the functioning of drug transporters is altered, such as by drug-drug interactions, by genetic polymorphisms, or as evidenced in knockout animals, the resulting change in volume of distribution can lead to a significant change in drug effect or likelihood of toxicity, as well as a change in half life independent of a change in clearance. Here, we review pharmacokinetic interactions at the transporter level that have been investigated in animals and humans and reported in literature, with a focus on the changes in distribution volume. We pay particular attention to the differing effects of changes in transporter function on the three measures of volume. Further, trends are discussed as they may be used to predict volume changes given the function of a transporter and the primary location of the interaction. Because the liver and kidneys express the greatest level and variety of transporters, we denote these organs as the primary location of transporter-based interactions. We conclude that the liver is a larger contributor to distribution volume than the kidneys, in consideration of both uptake and efflux transporters. Further, while altered distribution due to secondary interactions at tissues other than the liver and kidneys may have a pharmacodynamic effect, these interactions, at least at the blood-brain barrier, do not appear to significantly influence overall distribution volume. The analysis provides a framework for understanding potential pharmacokinetic interactions rooted in drug transporters as they modify drug distribution.     

Investigator Impact on Reproducibility of Drug Bioavailability in Stratum Corneum Sampling by Tape Stripping

Pharmaceutical Research - Skin sampling by tape stripping measures the local bioavailability of topical drug products in the stratum corneum (SC). The goal of the current study was to evaluate the...     

去甲异波尔定及其代谢产物的药动学与生物利用度研究

目的 研究去甲异波尔定静脉注射和灌胃给药后,其原型药物和主要代谢物去甲异波尔定-9-O-α-葡萄糖醛酸苷在大鼠体内的药动学特征和生物利用度。方法 以SD大鼠为模型动物,采用超高效液相色谱质谱检测法测定去甲异波尔定及其葡萄糖醛酸苷的血药浓度,并计算药动学参数。结果 去甲异波尔定及其葡萄糖醛酸苷的绝对生物利用度分别为2.77%和88.6%。大鼠静脉注射给药后,去甲异波尔定及其葡萄糖醛酸苷的药动学参数t_1/2分别为(42.16±36.56)和(275.26±176.89)min,AUC_0-t分别为(55.25±22.97)和(584.57±216.18)mg·min·mL^-1,ke分别为(0.024 9±0.012 9)和(0.003 7± 0.002 4)min^-1。大鼠灌胃给药后,去甲异波尔定及其葡萄糖醛酸苷的药动学参数Cmax分别为(0.14±0.03)和(13.80± 1.46)mg·mL^-1,T_max分别为(23.33±13.29)和(45.00±9.49)min,t_1/2分别为(30.20±11.04)和(313.79±181.20)min,AUC_0-t分别为(9.17±2.44)和(3 108.69±299.45)mg·min·mL^-1,k_e分别为(0.025 2±0.007 6)和(0.002 7±0.001 0)min^-1。统计学检验表明,静脉注射和灌胃给药后去甲异波尔定及其葡萄糖醛酸苷的t_1/2、AUC_0-t、T_max、C_max、k_e和MRT之间均有显著性差异(P<0.05)。结论 去甲异波尔定在体内生物转化迅速且生物利用度低。与原型药物相比,去甲异波尔定葡萄糖醛酸苷在体内的血药浓度较高且消除缓慢。     

拉莫三嗪代谢酶和转运体基因多态性对血药浓度的影响的研究进展

拉莫三嗪是一线抗癫痫药物,临床疗效和不良反应个体差异大与血药浓度有关,近年来寻找拉莫三嗪血药浓度差异的原因是研究的热点。本综述探讨了代谢酶和转运体基因多态性对拉莫三嗪血药浓度的影响,以期为拉莫三嗪个体化治疗提供参考依据。     

使用全自动包药机单剂量配发药品的经验体会

目的:分享如何使用全自动包药机单剂量配发药品及使用的经验体会。方法:介绍自动包药机的工作原理、使用环境和功能优势,结合实际操作分析使用中存在的问题,并对其使用前景予以展望。结果:该设备具有提高工作效率、降低调配差错率、方便患者使用的优势;但同时对软硬件环境提出了较高要求,且仍存在一定的局限性。结论:随着人们对医疗服务需求水平的提高,这种自动化设备的使用必将越来越广泛。     

肺癌患者脂质过氧化物代谢及保护酶类的研究

目的综合研究分析肺癌患者体内过氧化物代谢及抗氧化酶类的存在状态和相关性。方法采用紫外光度法及生物化学方法测定了肺癌患者、肺良性疾患患者和健康人血清GST、GSH-Px、CAT活性及LPO水平。结果肺癌组血清GST活性显著高于健康组和良性组(P<0.01)。健康组和良性组血清GST活性差异无显著性(P>0.05)。GSH-Px活性各組间均有显著性差异(P<0.05),健康组和肺癌组相比有极显著差异(P<0.01);各组间CAT活性无显著差异(P>0.05);LPO水平随病变进展明显升高,组间有极显著差异(P<0.01)。LPO/GSH-Px值随病变进展显著升高,组间有极显著性差异(P<0.01)。结论血GST和GSH-Px活性及LPO水平与疾病发生和发展之间可能存在量的关系。肺癌的发病或易感性可能与GSH-Px活性下降、GST活性和LPO水平显著升高有关。     

Reviewing the Connection Between Paradigms and Theories to Understand Adolescent Drug Use

Approaches to studying social phenomenon are fundamentally based upon personal beliefs about the nature of knowledge, reality, and order. Scholars, researchers, and practitioners can benefit from utilizing a coherent method that organizes the wide array of perspectives that exist and the theories, practice, prevention interventions, and policies that emerge. Although opinions regarding what constitutes real science vary, this article intends to demonstrate the utility of a multi-paradigmatic framework that may be used to organize theories that address adolescent drug use. Application of practice and implications for research, prevention interventions, and policy are presented.     

Evaluating the Impact of Physiological Properties of the Gastrointestinal Tract On Drug In Vivo Performance Using Physiologically Based Biopharmaceutics Modeling and Virtual Clinical Trials

The physiological properties of the gastrointestinal tract, such as pH, fluid volume, bile salt concentration, and gastrointestinal transit time, are highly variable in vivo. These properties can affect the dissolution and absorption of a drug, depending on its properties and formulation. The effect of gastrointestinal physiology on the bioperformance of a drug was studied in silico for a delayed-release pantoprazole tablet and an immediate-release dolutegravir tablet. Physiologically based absorption models were developed and virtual clinical trials were performed. Reasons for the variability in drug bioperformance between subjects were investigated, taking into account differences in gastrointestinal tract characteristics, pharmacokinetic parameters, and additional parameters (e.g., permeability). Default software parameters describing gastrointestinal physiology in the fasted and fed states, and variation in these parameters, were altered to match variability in these parameters reported in vivo. The altered model physiologies better described the variability of gastrointestinal conditions, and therefore the results of virtual trials using these physiologies are likely to be more relevant in vivo. With such altered gastrointestinal physiologies used to develop models, it is possible to obtain additional knowledge and improve the understanding of subject-formulation interactions.     

Dysregulation of Mucosal Membrane Transporters and Drug-Metabolizing Enzymes in Ulcerative Colitis

Intestinal transporters and metabolizing enzymes are the important factors of the intestinal absorption barrier. Because there is evidence that their expression and function may be affected during inflammatory conditions, we investigated gene expression, protein abundance, and regulation of relevant intestinal transporters and metabolizing enzymes in the intestinal mucosa of patients with ulcerative colitis (UC). Specimens from inflamed and noninflamed tissues of 10 patients with UC as well as colonic control tissues of 10 patients without inflammation were subjected to gene (9 enzymes, 15 transporters, 9 cytokines) and microRNA (N = 54) expression analysis. Protein abundance was quantified by liquid chromatography-tandem mass spectrometry–based targeted proteomics. Gene expression of several metabolizing enzymes (e.g., CYP2C9, UGT1A1) and transporters such as ABCB1 (ABCB1), ABCG2 (ABCG2), and monocarboxylate transporter 1 (MCT1, SLC16A1) were significantly decreased during inflammation and negatively correlated to microRNAs. On contrary, multidrug resistance-protein 4 (MRP4, ABCC4), organic anion–transporting polypeptide 2B1 (OATP2B1, SLCO2B1), and organic cation transporter-like 2 (ORCTL2, SLC22A18) were significantly elevated in inflamed tissue. However, at protein level, these findings could only be confirmed for MCT1. UC is associated with complex changes in the intestinal expression of enzymes, transporters, cytokines, and microRNAs, which may affect efficacy of anti-inflammatory drug therapy or the disease state itself.     

Bioavailability and Bioequivalence: Focus on Physiological Factors and Variability

This is a summary report of the EUFEPS & COST B25 conference on Bioavailability and Bioequivalence which focused on physiological factors and variability. This conference was held at The Royal Olympic Hotel in the centre of Athens (Greece) during the 1-2 of October in 2007. The issues discussed in the conference involved physiological factors affecting drug absorption, the role of pre-systemic effects on bioavailability (BA), the impact of variability in bioequivalence (BE) studies, and a final closing panel session on unresolved issues in BA/BE regulations. Several important aspects of drug absorption were highlighted. It was presented how the complexity of gastrointestinal (GI) physiology and the site dependent absorption can impact on drug BA. Similarly, the effects of food and formulation were also studied. The second session focused on integrating the complexities of GI into modeling the inter-individual variability of absorption and the prediction of first-pass metabolism from in-vitro data. The necessity to measure metabolites, the value of Biopharmaceutical Classification System (BCS), and the more recently proposed Biopharmaceutical Drug Disposition Classification System (BDDCS) were assessed as well. This session closed with presentations of pharmacokinetic software delegates. In the second day of the conference, the problem of high intra-subject variability in BE studies was analyzed. Study design considerations, the use of multiple-dose studies and the role of statistics in BE were also highlighted. Finally, the current thinking of regulatory authorities (EMEA and US-FDA) was presented. The conference closed with a last session on unresolved issues in the regulatory level.     

Influx and Efflux Transporters Contribute to the Increased Dermal Exposure to Active Metabolite of Regorafenib After Repeated Oral Administration in Mice

The multikinase inhibitor regorafenib, which is a standard treatment for certain cancer patients after disease progression following other approved therapies, exhibits delayed-onset dermal toxicity. Here, we aimed to clarify the mechanisms that contribute to the increased dermal exposure to active metabolite M-5 of regorafenib after repeated oral administration. The dermal concentration of M-5 at 24 h after the last 5 oral administrations of regorafenib in mdr1a/1b/bcrp^-/- mice was more than 190 times that in wild-type mice. The skin-to-plasma concentration ratio of M-5 in mdr1a/1b/bcrp^-/- was also higher than in wild-type mice, suggesting possible involvement of P-glycoprotein and breast cancer resistance protein in regulating the dermal distribution. The area under the plasma concentration-time curve values of M-5 and its precursor M-2 in plasma of mdr1a/1b/bcrp^-/- were at most 26 and 3 times those in wild-type mice, respectively. Interestingly, repeated administration of regorafenib markedly increased the area under the plasma concentration-time curve of M-5 in plasma, but not liver, compared with a single dose. Intravenous administration of M-5 dose-dependently reduced the liver-to-plasma concentration ratio. Our results indicate that hepatic uptake of M-5 may partially explain the accumulation of M-5 in the systemic circulation, but multiple factors, including influx and efflux transporters, are involved in determining dermal exposure to M-5.     

Modeling the Physiological Factors That Affect Drug Delivery from a Nipple Shield Delivery System to Breastfeeding Infants

An apparatus was designed to mimic lactation from a human breast. It was used to determine the influence of milk fat content and flow rate, and suction pulse rate of a breastfeeding infant upon the release of a model compound from a nipple shield delivery system (NSDS). The NSDS would be worn by a mother to deliver drugs and nutrients to her infant during breastfeeding. Sulforhodamine B dye (SB) was used as model compound and formulated as a dispersible tablet to be placed within the NSDS. Increasing suction pulse rate from 30 to 120 pulses/min  clearly correlated with increased cumulative release of SB for the same volume of milk passed through the NSDS. No distinct correlation was found between flow rates (1, 5, and 8 mL/min) and SB release, possibly because of competing factors controlling release rate at different flow rates. A highly similar SB release rate into two fat content fluids (2.9 and 4.2 wt%) was observed for identical flow conditions. This proof of concept study outlines a novel method to mimic lactation from a breast, and future studies will lead to effective methods to identify key physiological factors that influence drug release from a NSDS.     

How Spacing of Data Collection May Impact Estimates of Substance Use Trajectories

The goal of this study is to provide an empirical example using longitudinal cigarette smoking data that compares results of growth mixture trajectory models on the basis of contiguous and snapshot measurements. Data were drawn from an intensive longitudinal study of college freshman (N = 905) with a previous history of smoking. Participants provided weekly smoking reports for 35 consecutive weeks. We found that using contiguous weekly data (35 waves) or 6-wave or 4-wave snapshot data provided similar trajectory curves and proportions. However, there were notable differences in individual trajectory assignments on the basis of contiguous and snapshot measurements.