Development of a Method of Liquid Chromatography Coupled with Tandem Mass Spectrometry for Simultaneous Determination of Linezolid and Tedizolid in Human Plasma.

It is important to select appropriate antibiotics for infection control. Linezolid and tedizolid are newly developed and synthesized oxazolidinone antibacterial agents. It has been pointed out that there is a relationship between a high plasma concentration of the target drug and incidence of adverse effects, although it has been reported that neither linezolid nor tedizolid requires dose adjustment according to renal function. Due to the high incidence of adverse effects, both are often switched. Precise plasma concentration control by therapeutic drug monitoring (TDM) is desirable for reducing the adverse effects of both drugs and obtaining a better therapeutic effect. In this study, we aimed to establish a method for simultaneous quantification of linezolid and tedizolid in human plasma using LC coupled with tandem mass spectrometry. Sample preparation was performed by a simple operation with acetonitrile. Linezolid and tedizolid were separated by an octadecylsilyl column using a gradient elution of acetonitrile in aqueous 0.1% formic acid solution and were detected in the positive ion electrospray mode with multiple reaction monitoring. Quantification of linezolid and tedizolid ranged from 0.5 to 50 and 0.5 to 20 µg/mL, respectively. The intra-day and inter-day precision and accuracy of data were assessed and found to be acceptable. The developed method was successfully applied to measurement of the concentrations of linezolid and tedizolid. This simple method, which can simultaneously quantify both drug concentrations for daily TDM, could contribute to safer treatment of patients.

Evaluation of various tissue-clearing techniques for the three-dimensional visualization of liposome distribution in mouse lungs at the alveolar scale.

PURPOSE: To develop a three-dimensional visualization method for evaluating the distribution of pulmonary drug delivery systems and compare four tissue-clearing techniques (ClearT2, CUBIC, ScaleS, and SeeDB2) using intrapulmonary liposomes as drug carriers. METHODS: Rhodamine B-labeled liposomes were administered intrapulmonarily to mice using a MicroSprayer, and then fluorescent-labeled tomato lectin was administered intravenously to visualize the general lung structure. Tissue-clearing treatment of the mouse lungs was performed using the standard protocols of the ClearT2, CUBIC, ScaleS, and SeeDB2 techniques. Lung clearing was clarified using laser-scanning confocal microscopy, and three-dimensional images were reconstructed. RESULTS: Fluorescent-labeled tomato lectin was preserved using ClearT2 and SeeDB2 but not using CUBIC and ScaleS. In addition, the liposomes were stable in ClearT2 reagent, but they were mostly degraded in other reagents by surface-active agents. ClearT2 treatment enabled the three-dimensional visualization of intrapulmonary rhodamine B-labeled liposomes at the alveolar scale. CONCLUSIONS: These results suggest that the ClearT2 tissue-clearing technique was appropriate for the three-dimensional visualization of intrapulmonary liposomes at the alveolar scale. This study provides important information for selecting and optimizing suitable optical tissue-clearing techniques in lungs for evaluating the distribution of pulmonary drug delivery systems.

Tissue-Clearing Techniques Enable Three-Dimensional Visualization of Aerosolized Model Compound and Lung Structure at the Alveolar Scale.

In this study, we examined the usefulness of a tissue-clearing technique for the evaluation of the lung distribution of aerosolized drugs. An aerosol formulation of TexasRed dextran (70 kDa), a model compound of drug carrier for aerosolized drugs, was administered intrapulmonarily to mice using a MicroSprayer, and then DyLight 488-conjugated tomato lectin was administered intravenously to visualize general lung structure via the fluorescent labeling of alveolar and bronchial epithelial cells. Tissue clearing followed by laser scanning confocal microscopy enabled the three-dimensional visualization of intrapulmonary TexasRed dextran and the evaluation of its distribution at the alveolar scale without the preparation of thin tissue sections. These findings suggest that tissue-clearing techniques are useful for the evaluation of intrapulmonary distribution and development of pulmonary drug delivery systems.