Jaswanth Kumar Inamadugu

The authors proposed a simple, rapid and sensitive liquid chromatography / tandem mass spectrometry assay method for the determination of nateglinide in human plasma using carbamazepine as internal standard (IS). Analyte and the IS were extracted from the human plasma via liquid-liquid extraction using ethyl acetate. The chromatographic separation was achieved on a C18 column by using a mixture of 0.1% formic acid buffer –acetonitrile buffer (20:80, v/v) as the mobile phase at a flow rate of 0.8 mL/min. The calibration curve obtained was linear (r2 ³ 0.99) over the concentration range of 10.0–10005 ng/mL. Method validation was performed as per FDA guidelines and the results met the acceptance criteria. The proposed method was found to be applicable to pharmacokinetic studies.

There is interest in evaluating the efficacy of lower doses of certain thiazolidinedione family or insulin sensitizers for clinical care. We have developed a sensitive and rapid positive polarity electro-spray ionization with Tandem-mass spectrometry method was validated as per FDA guidelines for the determination of Pioglitazone (PGZ), their metabolites Keto-Pioglitazone (KPGZ) and Hydroxy-Pioglitazone (HPGZ) in human plasma samples. Glyburide was used as an internal standard. The chromatographic separation was achieved by Discovery C18 column using isocratic mobile phase consists a mixture of 5mM ammonium acetate (pH 6.4 ± 0.1) and acetonitrile (40:60 v/v). An aliquot of 150 µL plasma was used for the liquid- liquid plasma extraction technique for quantification of the analytes. The molecular ion Q1, product ion Q3 transitions for Pioglitazone, Keto-Pioglitazone and Hydroxy-Pioglitazone were found to be 357.2→134.1, 371.3→148.4 and 373.2→150.1 m/z respectively. The proposed method was validated in the concentration range of 10.0-3529.0, 5.0-1209.7 and 5.0-2029.7 ng/mL for PGZ, KPGZ and HPGZ respectively in multiple reaction monitoring mode. The pharmacokinetic parameters for Pioglitazone were found to be Tmax - 2.5 Hours, Cmax - 2088.2 ng/mL, T1/2 - 6.5 Hours, AUC (0-T) - 20925.9 ng/mL and AUC (0-∞) - 21276.2 ng/mL). The entire results obtained in the study were well within acceptance limits.

  A rapid and sensitive liquid chromatography-tandem mass spectrometric (LC-MS/MS) assay method has been developed and fully validated for simultaneous quantification of two lipid lowering agents rosuvastatin and fenofibric acid in human plasma. Lovastatin was used as an internal standard. Analytes and the internal standard were extracted from human plasma by liquid-liquid extraction technique using a 50:50, v/v mixture of ethyl acetate and diethyl ether. The reconstituted samples were chromatographed on a C18 column by using a 80:20, v/v mixture of acetonitrile and 0.1% formic acid as the mobile phase at a flow rate of 1.0 mL/min. The calibration curve obtained was linear (r2 ³ 0.99) over the concentration range of 0.10-80.00 ng/mL for rosuvastatin and 50-9003 ng/mL for fenofibric acid. The multiple reaction monitoring mode was used for quantification of ion transitions at m/z 482/258, 319/233 and 405/199 for the rosuvastatin, fenofibric acid and the internal standard, respectively. The results of the intra-day and inter-day precision and accuracy study results were well within the acceptable limits. A run time of 3.0 min for each sample made it possible to analyze more than 300 plasma samples per day. The proposed method was successfully applied for the determination of the fenofibric acid in real time plasma samples for pharmacokinetic studies. Key words: Rosuvastatin, Fenofibric acid, human plasma, LC-MS/MS quantification, Pharmacokinetics.