A sensitive, accurate and selective liquid chromatography-tandem mass spectrometry method (LC-MS/MS) was developed and validated for the simultaneous quantitation of atorvastatin (AT) and its equipotent hydroxyl metabolites, 2-hydroxy atorvastatin (2-AT) and 4-hydroxy atorvastatin (4-AT), in human plasma. Electrospray ionization (ESI) interface in negative ion mode was selected to improve the selectivity and the sensitivity required for this application. Additionally, a solid phase extraction (SPE) step was performed to reduce any ion-suppression and/or enhancement effects. The separation of all compounds was achieved in less than 6 min using a C18 reverse-phase fused-cores column and a mobile phase, composed of a mixture of 0.005%formic acid in water:acetonitrile:methanol (35:25:40, v/v/v), in isocratic mode at a flow rate of 0.6 mL/min. The method has lower limit of quantitation (LLOQ) of 0.050 ng/mL for all analytes. The method has shown tremendous reproducibility, with intra-and inter-day precision less than 6.6%, and intra- and inter-day accuracy within 74.3% of nominal values, for all analytes, and has proved to be highly reliable for the analysis of clinical samples.

An analytical method based on solid phase extraction was developed and validated for analysis of adefovir in human plasma. Adefovir-d4 was used as an internal standard and Synergi MAX RP80A (150 mm × 4.6 mm, 4μm) column provided the desired chromatographic separation of compounds followed by detection with mass spectrometry. The method used simple isocratic chromato-graphic condition and mass spectrometric detection in the positive ionization mode. The calibration curves were linear over the range of 0.50–42.47 ng/mL with the lower limit of quantitation validated at 0.50 ng/mL. Matrix effect was assessed by post-column infusion experiment to monitor phospholipids and post-extraction addition experiment was performed. The degree of matrix effect for adefovir was determined as 7.5%and ion-enhancement in five different lots of human plasma was 7.1%and had no impact on study samples analysis with 4.5 min run time. The intra- and inter-day precision values were within 7.7% and 7.8%, respectively, for adefovir at the lower limit of quantification level. Validated bioanalytical method was successfully applied to clinical sample analysis.

PURPOSE: This study was designed to characterize the pharmacokinetic profile and to assess bioequivalence of the sponsor's test formulation (imatinib mesylate 400 mg tablets) with an innovator product (Gleevec 400 mg tablets, Novartis Pharmaceuticals) under fed conditions, in adult patients of Philadelphia chromosome positive chronic myeloid leukemia (Ph+ CML) stabilized on imatinib mesylate 400 mg. In addition, the aim of this study was to monitor the safety profile of investigational medicinal products (IMPs). MATERIALS AND METHODS: A multicenter, randomized, open label, two-period, crossover, single dose bioequivalence study was designed for conduct under fed conditions in 42 adult Ph+ CML patients already stabilized on imatinib 400 mg tablets. Pharmacokinetic parameters Tmax, Cmax, and AUC0-24 were calculated using a non-compartmental model on validated WinNonlin software. Validated SAS software was used for statistical evaluation of data. The safety profile of investigational products was monitored during the course of study by applying a clinical process for recording observed untoward effects postadministration of investigational products. RESULTS: The 90% confidence intervals for the test/reference mean ratios of the ln-transformed PK variables Cmax (99.0%) and AUC0-24 (99.2%) were within an acceptable range of 80%-125%, as per bioequivalence assumptions. Both formulations were well tolerated after oral administration of IMPs. CONCLUSION: The test product was found to be bioequivalent and safe, and thus can be used interchangeably in clinical practice.
Administration, Oral ; Adult ; Humans ; Imatinib Mesylate* ; Leukemia ; Leukemia, Myelogenous, Chronic, BCR-ABL Positive* ; Mesylates ; Pharmacokinetics ; Philadelphia Chromosome ; Tablets* ; Therapeutic Equivalency*