A dried blood spot assay for paclitaxel and its metabolites

After being used for decades in clinical screening, dried blood spots (DBS) have recently received considerable attention for their application in pharmacokinetic and toxicokinetic studies in rodents. The goal of this study was to develop and apply a DBS-based assay for a pharmacokinetic study of paclitaxel (PTX) and its metabolites in SCID/Beige mice. A fast and sensitive UHPLC-MS/MS method has been developed for the simultaneous determination of PTX, its three metabolites (6 alpha-hydroxy-paclitaxel, 3'-p-hydroxypacli taxel, and 6a,3'-p-dihydroxy-paclitaxel) and its stereoisomer 7-epi-p aclitaxel. The 10 mu L DBS sample was extracted with methanol for 20 min at 37 degrees C. After dilution of the extracts with water in a ratio of 1:1, the analytes were separated on a reversed-phase 2.1 mm I.D. column using gradient elution. The total run time was 2.5 min. The analytes were detected by use of multiple reaction monitoring mass spectrometry. The extraction recoveries of the compounds were all greater than 60%, resulting in a quantification limit of 1 ng/ml. The calibration curves ranged from 1 to 1000 ng/ml. The intra-day and inter-day imprecision (%CV) across three validation runs over four quality control levels were less than or equal to 14.6%. The accuracy was within +/-11.9% in terms of relative error. The described method is advantageous in terms of its ease-of-use and speed compared to other published PTX assays. The method's usefulness was demonstrated by applying it to a preclinical pharmacokinetic investigation of PTX and its metabolites in SCID/Beige mice with an intraperitoneal administration of 50 mg/kg Abraxane (R)

Instructing implicit processes: when instructions to approach or avoid influence implicit but not explicit evaluation

Previous research has shown that linking approach or avoidance actions to novel stimuli through mere instructions causes changes in the implicit evaluation of these stimuli even when the actions are never performed. In two high-powered experiments (total N=1147), we examined whether effects of approach-avoidance instructions on implicit evaluations are mediated by changes in explicit evaluations. Participants first received information about the evaluative properties of two fictitious social groups (e.g., Niffites are good; Luupites are bad) and then received instructions to approach one group and avoid the other group. We observed an effect of approach avoidance instructions on implicit but not explicit evaluations of the groups, even when these instructions were incompatible with the previously obtained evaluative information. These results indicate that approach avoidance instructions allow for unintentional changes in implicit evaluations. We discuss implications for current theories of implicit evaluation. (C) 2015 Elsevier Inc. All rights reserved

The Other Press, February 1, 1984

Cisplatin is a first-line chemotherapeutic for the treatment of a wide variety of cancers since its discovery in the 1960s. Although various techniques have been reported for the measurement of total platinum in biological matrices, such as inductively coupled plasma-mass spectrometry and derivatization procedures, a specific, sensitive and robust assay for the quantification of intact cisplatin is still lacking. Therefore, we present a rapid, selective, sensitive, and reliable UHPLC-MS/MS based method for the determination of intact cisplatin in human plasma in support of a Phase II clinical trial. The optimal chromatographic behavior of cisplatin was achieved on a Syncronis HILIC column (50 x 2.1 mm, 1.7 mu m, zwitterionic stationary phase). The retention behavior of cisplatin on this zwitterion-based stationary phase was well described by an adsorptive interaction model. A simple sample preparation based on protein precipitation combined with the removal of phospholipids by HybridSPE-precipitation was developed. The method was proven to be free of a relative matrix effect. The assay was validated within a range of 20 - 10,000 ng/mL using 100 mu L of plasma sample. The intra and inter day precisions were all less than 7.6%, and none of the bias was greater than 13.1%, thus corroborating that the developed method is precise and accurate. As a proof of concept, the assay has been successfully applied to plasma samples obtained from different patients who were enrolled in the Phase II trial and were treated with cisplatin

Physiology-based IVIVE predictions of tramadol from in vitro metabolism data

To predict the tramadol in vivo pharmacokinetics in adults by using in vitro metabolism data and an in vitro-in vivo extrapolation (IVIVE)-linked physiologically-based pharmacokinetic (PBPK) modeling and simulation approach (SimcypA (R)). Tramadol metabolism data was gathered using metabolite formation in human liver microsomes (HLM) and recombinant enzyme systems (rCYP). Hepatic intrinsic clearance (CLint(H)) was (i) estimated from HLM corrected for specific CYP450 contributions from a chemical inhibition assay (model 1); (ii) obtained in rCYP and corrected for specific CYP450 contributions by study-specific intersystem extrapolation factor (ISEF) values (model 2); and (iii) scaled back from in vivo observed clearance values (model 3). The model-predicted clearances of these three models were evaluated against observed clearance values in terms of relative difference of their geometric means, the fold difference of their coefficients of variation, and relative CYP2D6 contribution. Model 1 underpredicted, while model 2 overpredicted the total tramadol clearance by -27 and +22%, respectively. The CYP2D6 contribution was underestimated in both models 1 and 2. Also, the variability on the clearance of those models was slightly underpredicted. Additionally, blood-to-plasma ratio and hepatic uptake factor were identified as most influential factors in the prediction of the hepatic clearance using a sensitivity analysis. IVIVE-PBPK proved to be a useful tool in combining tramadol's low turnover in vitro metabolism data with system-specific physiological information to come up with reliable PK predictions in adults

A semiphysiological population pharmacokinetic model of agomelatine and its metabolites in Chinese healthy volunteers

Aims: Agomelatine is an antidepressant for major depressive disorders. It undergoes extensive first-pass hepatic metabolism and displays irregular absorption profiles and large interindividual variability (IIV) and interoccasion variability of pharmacokinetics. The objective of this study was to characterize the complex pharmacokinetics of agomelatine and its metabolites in healthy subjects. Methods: Plasma concentration-time data of agomelatine and its metabolites were collected from a 4-period, cross-over bioequivalence study, in which 44 healthy subjects received 25 mg agomelatine tablets orally. Nonlinear mixed effects modelling was used to characterize the pharmacokinetics and variability of agomelatine and its metabolites. Deterministic simulations were carried out to investigate the influence of pathological changes due to liver disease on agomelatine pharmacokinetics. Results: A semiphysiological pharmacokinetic model with parallel first-order absorption and a well-stirred liver compartment adequately described the data. The estimated IIV and interoccasion variability of the intrinsic clearance of agomelatine were 130.8% and 28.5%, respectively. The IIV of the intrinsic clearance turned out to be the main cause of the variability of area under the curve-based agomelatine exposure. Simulations demonstrated that a reduction in intrinsic clearance or liver blood flow, and an increase in free drug fraction had a rather modest influence on agomelatine exposures (range: -50 to 200%). Portosystemic shunting, however, substantially elevated agomelatine exposure by 12.6-109.1-fold. Conclusions: A semiphysiological pharmacokinetic model incorporating first-pass hepatic extraction was developed for agomelatine and its main metabolites. The portosystemic shunting associated with liver disease might lead to significant alterations of agomelatine pharmacokinetics, and lead to substantially increased exposure

Quantum interferometric optical lithography:towards arbitrary two-dimensional patterns

As demonstrated by Boto et al. [Phys. Rev. Lett. 85, 2733 (2000)], quantum lithography offers an increase in resolution below the diffraction limit. Here, we generalize this procedure in order to create patterns in one and two dimensions. This renders quantum lithography a potentially useful tool in nanotechnology.Comment: 9 pages, 5 figures Revte