Recent advances in preclinical in vitro approaches towards quantitative prediction of hepatic clearance and drug-drug interactions involving organic anion transporting polypeptide (OATP) 1B transporters

Hepatic uptake mediated by organic anion transporting polypeptide (OATP) 1B1 and 1B3 can serve as a major elimination pathway for various anionic drugs and as a site of drug-drug interactions (DDIs). This article provides an overview of the in vitro approaches used to predict human hepatic clearance (CL_h) and the risk of DDIs involving OATP1Bs. On the basis of the so-called extended clearance concept, in vitro–in vivo extrapolation methods using human hepatocytes as in vitro systems have been used to predict the CL_h involving OATP1B-mediated hepatic uptake. CL_h can be quantitatively predicted using human donor lots possessing adequate OATP1B activities. The contribution of OATP1Bs to hepatic uptake can be estimated by the relative activity factor, the relative expression factor, or selective inhibitor approaches, which offer generally consistent outcomes. In OATP1B1 inhibition assays, substantial substrate dependency was observed. The time-dependent inhibition of OATP1B1 was also noted and may be a mechanism underlying the in vitro–in vivo differences in the inhibition constant of cyclosporine A. Although it is still challenging to quantitatively predict CL_h and DDIs involving OATP1Bs from only preclinical data, understanding the utility and limitation of the current in vitro methods will pave the way for better prediction.     

Misdiagnosis of attention deficit hyperactivity disorder: ‘Normal behaviour’ and relative maturity

Attention deficit hyperactivity disorder (ADHD) is one of the most frequently diagnosed disorders in children, yet it remains poorly understood. Substantial controversy exists regarding correct diagnosis of ADHD, and areas of subjectivity in diagnosis have been identified. Concerns for appropriate diagnosis are critical in terms of children’s educational outcomes, as well as health concerns associated with the use and potential overuse of stimulant medications. There exists a relative-age effect in which children who are relatively younger than their peers and born closest to the school start age cut-off are more frequently diagnosed and treated for ADHD. Additionally, substantial variation exists in ADHD diagnosis between boys and girls, with boys often presenting with more stereotypical symptoms. Both the relative-age effect and variation in sex diagnosis, as well as the challenges of early preschool diagnosis, emphasize the importance of considering relative maturity in ADHD diagnosis of children. Implications and knowledge translation strategies for practitioners, parents and the education system are presented.     

Ill-health as a household norm: Evidence from other people's health problems

This paper proposes that an individual's self-assessed health (SAH) does not only suffer from systematic reporting bias and adaptation bias but is also biased owing to confounding health norm effects. Using 13 waves of the British Household Panel Survey covering the period 1991–2005, I show that, while there is a negative and statistically significant correlation between SAH and individuals' own health problem index, this negative effect reduces with the average number of health problems per (other) family member. The relative health bias is small, however, which implies that measures of SAH may not suffer seriously from systematic health norm bias. This is an important finding for researchers working with SAH data as it indicates that we do not have to worry too much about controlling for confounding influences from the health of other household members when estimating SAH regression equations.     

美国头颈癌患者生存资料分析

为使国内头颈癌生存分析的基本方法与国际一致，规范生存率分析的基本方法，以利于相互比较．本文以文字及表格方式，简述生存分析基本术语的概念、意义和应用，并介绍2002年第6版《美国头颈部肿瘤TNM分期》的1-5年观察生存率、相对生存率。     

Different impacts of intestinal lymphatic transport on the oral bioavailability of structurally similar synthetic lipophilic cannabinoids: Dexanabinol and PRS-211,220

The aim of this article was to investigate the role of intestinal lymphatic transport in the oral bioavailability of two structurally similar synthetic lipophilic cannabinoids: dexanabinol and PRS-211,220. For this purpose, the long chain triglyceride (LCT) solubility and affinity to chylomicrons ex vivo of both cannabinoids were evaluated. Their oral bioavailability was assessed in rats following administration in a lipid-free and a LCT-based formulation. The intestinal lymphatic transport of these two molecules was also directly measured in a freely moving rat model. LCT solubility of dexanabinol and PRS-211,220 was 7.9 ± 0.2 and 95.8 ± 5.3 mg/g, respectively. The uptake by chylomicrons was moderate (31.6 ± 5.2%) and high (66.1 ± 2.4%), respectively. The bioavailability of dexanabinol (37%) was not affected by LCT solution, whereas administration of PRS-211,220 in LCT improved the absolute oral bioavailability three-fold (from 13 to 35%) in comparison to the lipid-free formulation. The intestinal lymphatic transport of dexanabinol and PRS-211,220 was 7.5 ± 0.8 and 60.7 ± 6.8% of the absorbed dose, respectively. In conclusion, despite structural similarity and similar lipophilicity, dexanabinol and PRS-211,220 exhibited a very diverse pattern of oral absorption, and the lymphatic system played quite a different role in the oral bioavailability of these molecules. The low lymphatic transport of dexanabinol is likely driven by relatively lower affinity to chylomicrons and lower LCT solubility.     

Development of HPLC plasma assays for CAM 4515 and CAM 4750, two new nonpeptide tachykinin antagonists, and application to bioavailability studies

CAM 4515 and CAM 4750 are new nonpeptide tachykinin NK₁ receptor antagonists with different lipophilicities. Two separate, simple, and sensitive HPLC methods for the quantitation of these two compounds in plasma and the evaluation of their oral bioavailability in rats were developed and validated. Extraction of CAM 4515 from plasma involved protein precipitation with acetonitrile, while that for CAM 4750 involved a one-step liquid-liquid extraction with methylene chloride. The analytes in extracts were chromatographed on a C18 column using two different separation buffers, 47% 0.02 M sodium citrate (pH 3.5)-53% acetonitrile for CAM 4515 and 59% 0.02 M potassium phosphate dibasic (pH 7.0)-41% acetonitrile for CAM 4750, and both compounds were detected by fluorescence (excitation 278 nm; emission 342 nm). Stability profiles of both drugs at −20°C or room temperature in plasma and in reconstituted buffers were good. The limit of quantitation for both drugs was 5 ng ml⁻¹ with good linearity from 5 to 1000 ng ml⁻¹ using 100–200 μl of plasma. Excellent precision (relative standard deviation < 8.3%) and accuracy (relative error ± 9.2%) were observed for both CAM 4515 and CAM 4750. Oral bioavailability studies were conducted for each compound in rats receiving a p.o. dose of 20 mg kg⁻¹ and an i.v. dose of 5 mg kg⁻¹. The absolute oral bioavailability of CAM 4750 (80%) was estimated to be 40-fold greater than that of CAM 4515 (2%). The experimental results suggest that incorporation of a pyridine group into the structural backbone may greatly improve bioavailability.     

氟罗沙星片剂,胶囊剂的人体药物动力学和相对生物利用度研究

9名男性健康自愿受试者采用三交叉单剂口服国产氛罗沙星片剂、胶囊和进口氟罗沙星片剂各400mg的药代动力学参数比较。血、尿药浓度用HPLC检测．结果表明：体内过程符合一室模型，主要药代动力学参数分别为：AUC：82.30±14．30、81．13±8．45与83．92±14.27h·mg／L；Cmax：4．71±0．83、4．67±0．51与4．86±0．89mg／L；Tmax：1．88±0．44、1．90±0．39与1．92±0．23h；T1／2ke：11．02±0．96、10．93±0．68与10．86±0．82h；V／F（c）：79．08±13．31、78.42±8．70与76．39±12．93L；Cl／F：5．00±0．98、4．98±0．52与4．88±0．73L／h。服药48h的尿中原型药排出率分别为给药量的57．4％，55．9％和60．7％。国产氧罗沙星片剂和胶囊口服后药物动力学参数与进口片剂相仿．其相对生物利用及分别为98.07％与96．68％。     

The bioavailability and nonlinear pharmacokinetics of MK-679 in humans

MK-679 (R(?)-3-((3-(2-(7-chloro-2-quinolinyl)ethenyl)phenyl)(3-(dimethylamino)-3-oxopropyl)thio)methyl)thio(propanoic acid) is a potent and specific LTD₄-receptor antagonist. The disposition of MK-679 was investigated in a three-way crossover study in 12 healthy males receiving single intravenous doses of 75, 250, and 500 mg of MK-679. A greater than proportional increase in the area under the plasma concentration—time curve of MK-679 was observed with increase in dose. The plasma concentration data for each subject fitted well to the differential equations for a two-compartment model with linear tissue distribution and Michaelis-Menten elimination from the central compartment, indicating that the elimination of MK-679 in humans is saturable. In a previous study, the disposition of MK-679 in humans was also dose-dependent when given together with its S(+)-isomer, L-668,018. Thus, the disposition of MK-679 in humans is dose-dependent regardless of the presence of its stereoisomer. Also, the bioavailability of MK-679 was determined in six healthy males receiving simultaneously an oral dose of 250 mg of MK-679 and intravenous infusion of 1 mg ¹⁴C-MK-679. Results of this study indicate that the oral bioavailability of MK-679 is nearly quantitative.     

Bioavailability of intramuscularly administered tenoxicam

Bioavailability of intramuscularly administered tenoxicam relative to single oral and relative to intravenous doses was determined in two separate randomized crossover studies. Twelve healthy volunteers (12 males, age 20–30 years) received a rapid intravenous injection and a single intramuscular dose and 12 other subjects (11 males, 1 female, age 21–25 years) a single oral and a single intramuscular dose of 20 mg of tenoxicam on two different occasions. The wash-out period between the two consecutive treatments was 4 weeks. Plasma concentrations after dosing were determined by a specific HPLC method. Differences in tenoxicam concentration-time profiles after the different routes of administration were limited to the first 2 h after dosing. Later, plasma concentrations were almost superimposable within and across the two studies. The extent of absorption of intramuscularly administered tenoxicam was complete (mean ± CV per cent: F_abs 0.99 ± 20 per cent) with no difference between the two extravascular administrations (F_rel 0.95 ± 10 per cent, intramuscular vs oral). After intramuscular administration tenoxicam was more rapidly absorbed compared to the oral dose (T_max 0.71 h ± 80 per cent vs 1.4 h ± 62 per cent; p>0.05). Peak concentrations after oral and intramuscular administration (C_max 2.5 mg 1^?1 ± 19 per cent vs 2.7 mg l^?1 14 per cent; p <0.05) were very similar.     

头孢他美酯分散片在人体内的相对生物利用度及生物等效性

目的建立HPLC法测定人血浆中头孢他美的浓度,并研究头孢他美酯分散片在人体内的相对生物利用度及生物等效性。方法18名受试者随机均分成两组,先后单剂量po受试制剂或参比制剂后,采用HPLC法测定血药浓度,计算药动学参数并进行生物等效性判定。结果单次服用0.5 g受试制剂或参比制剂后的药动学参数AUC0→14、AUC0→∞、Tm ax、Cm ax、t1/2分别为22.07±3.98μg.h.m l-1和21.31±4.37μg.h.m l-1,22.62±4.06μg.h.m l-1和21.99±4.54μg.h.m l-1,2.42±0.55 h和2.61±0.50 h,4.16±0.74μg.m l-1和3.95±0.87μg.m l-1,2.24±0.26 h和2.48±0.33 h。实验制剂对参比制剂的相对生物利用度为105.0%±14.6%。两种制剂的药动学参数无明显差异。结论受试制剂与参比制剂具有生物等效性。