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.     

Investigation of non-linear Mate1-mediated efflux of trimethoprim in the mouse kidney as the mechanism underlying drug-drug interactions between trimethoprim and organic cations in the kidney

The purpose of this study was to elucidate the involvement of Mate1 in the tubular secretion of trimethoprim and saturation of Mate1-mediated efflux to address the mechanisms underlying the pharmacokinetic drug interactions with trimethoprim. Trimethoprim is a more potent inhibitor of MATE2-K than MATE1 with K_i values (μM) of 0.030–0.28 and 2.4–5.9, respectively. Trimethoprim is a substrate of human MATE1 and MATE2-K with K_m values of 2.3 ± 0.9 and 0.018 ± 0.004 μM, and mouse Mate1, but not human OCT2, mouse Oct1 and Oct2. Pyrimethamine significantly reduced the renal clearance (CL_R) of trimethoprim (mL/min/kg) from 40.0 ± 5.1 to 20.1 ± 3.7 (p < 0.05). Trimethoprim was given to mice at three infusion rates (150, 500, and 1500 nmol/min/kg). Together with an increase in the plasma concentrations of trimethoprim, the CL_R (mL/min/kg) of trimethoprim decreased to 25.9 ± 3.2, 13.5 ± 5.7, and 8.92 ± 1.50 at the respective rates. Trimethoprim decreased the CL_R of rhodamine 123 in an infusion rate-dependent manner: 11.5 ± 1.3 (control), 5.17 ± 1.55, 1.31 ± 0.50, and 0.532 ± 0.180. These results suggest that Mate1 mediates the tubular secretion of trimethoprim, and at therapeutic doses, MATEs-mediated efflux can be saturated, and thereby, cause drug interactions with other MATE substrates.     

Glycopolymer Code: Programming Synthetic Macromolecules for Biological Targeting

Targeting in a cellular level is still one of the major challenges in biomedical treatments. However, new synthetic and analytical techniques now allow the development of precisely prepared macromolecules. Thus, glycopolymer chains are reported to be prepared with controlled length, monomer sequences, as well as chain‐folded structures. A high level of complexity in synthetic macromolecules also allows increased selectivity in targeting, which is a key factor in biomedical applications.     

西咪替丁对林可霉素生物利用度的影响

通过8名健康志愿者服药后的对照实验,用微生物法检测血药浓度,按一室模型配置求算药物动力学参数,探讨西咪替丁对林可霉素体内过程的影响。结果表明,西咪替丁不能改变林可霉素的吸收速率(Ka)和消除速率(Ke),但可通过增加其吸收程度或改变其分布容积,使林可霉素的血药浓度和生物利用度分别增加约19％和27％。