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-core® 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 ±4.3% of nominal values, for all analytes, and has proved to be highly reliable for the analysis of clinical samples.
This study aimed to investigate the bioequivalence of 2 formulations of gliclazide modified-release tablets 60 mg in 48 healthy Caucasian volunteers under fasting conditions. A test product, Gliclazide MR (Ranbaxy Laboratories Limited, now Sun Pharmaceutical Industries, India), was compared with a reference product, Diamicron MR (Servier, France). The study was performed under a single-dose, 2-treatment, 2-period, 2-sequence crossover design in a fasted condition with a washout period of 21 days. Blood samples were collected for 96 hours after drug administration. Drug plasma concentrations were determined by a liquid chromatography-tandem mass spectrometry method. Analysis of pharmacokinetic characteristics was based on a noncompartmental model. The logarithmically transformed data of C and AUC were analyzed for 90% confidence intervals using analysis of variance. There was no significant difference in pharmacokinetic characteristics between the products, and the 90% confidence intervals were within the acceptance range of 80.00%-125.00%. The investigated products were bioequivalent under fasted conditions.
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