Quantification of Duloxetine in the Bacterial Culture and Medium to Study Drug-gut Microbiome Interactions.

Expanding our understanding of drug-gut bacteria interactions requires high-throughput drug measurements in complex bacterial cultures. Quantification of drugs in the cultures, media, and cell pellets is prone to strong matrix effects. We have developed a liquid chromatography-high resolution mass spectrometry (LC-HRMS) method for quantifying duloxetine from high-throughput gut-drug interaction experiments. The method is partially validated for its reproducibility, sensitivity, and accuracy, which makes it suitable for largescale drug screens. We extensively used this method to study biotransformation and bioaccumulation of duloxetine and other drugs in several species of gut bacteria.

Liquid chromatography-tandem mass spectrometry quantification of levosulpiride in human plasma and its application to bioequivalence study.

An improved method for determining levels of levosulpiride in human plasma using ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was developed and validated. The protein precipitation method was used for plasma sample preparation. Levosulpiride and an internal standard (IS) were isocratically separated on a UPLC BEH C(18) column with a mobile phase of ammonium formate buffer (1mM, adjusted to pH 3 with formic acid) and acetonitrile (60:40, v/v). MS/MS detection was performed by monitoring the parent-->daughter pair of levosulpiride and the IS at m/z 342-->112 and 329-->256, respectively. The method was linear from 2.5 to 200ng/mL and exhibited acceptable precision and percent recovery. The method was successfully demonstrated in pharmacokinetic and bioequivalence studies of two levosulpiride oral formulations administered to healthy volunteers. When compared to the previous LC-MS methods, the proposed method is faster, well-validated, and uses lesser plasma volume and a similar sensitivity. The use of UPLC allowed rapid and sensitive quantification of levosulpiride, making this method suitable for high-throughput clinical applications.

Revival of TE2A; a better chelate for Cu(II) ions than TETA?

A highly effective synthetic route for TE2A was developed and the (64)Cu-labeled TE2A complexes showed higher kinetic inertness and faster clearance than most commonly used TETA analogs.

Rapid determination of finasteride in human plasma by UPLC-MS/MS and its application to clinical pharmacokinetic study.

A rapid, specific, and sensitive method utilizing reversed-phase ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) was developed and validated to determine finasteride levels in human plasma. The plasma samples were prepared by liquid-liquid extraction with ethyl acetate, evaporation, and reconstitution. MS/MS analyses were performed on a triple-quadrupole tandem mass spectrometer by monitoring protonated parent-->daughter ion pairs at m/z 373-->305 for finasteride and m/z 237-->194 for carbamazepine (internal standard, IS). The method was validated with respect to linearity, recovery, specificity, accuracy, precision, and stability. The method exhibited a linear response from 0.1 to 30 ng/mL (r(2)>0.998). The limit of quantitation for finasteride in plasma was 0.1 ng/mL. The relative standard deviation (RSD) of intra- and inter-day measurements was less than 15% and the method was accurate within -6.0% to 2.31% at all quality-control levels. The mean extraction recovery was higher than 83% for finasteride and 84% for the IS. Plasma samples containing finasteride were stable under the three sets of conditions tested and the processed samples were stable up to 29 h in an autosampler at 5 degrees C. Detection and quantitation of both analytes within 3 min make this method suitable for high-throughput analyses. The method was successfully applied to a pharmacokinetic study of finasteride in healthy volunteers following oral administration.