Development and validation of bioanalytical method for quantification of cycloserine in human plasma by liquid chromatography-tandem mass spectrometry: Application to pharmacokinetic study.

A selective, sensitive and high-throughput liquid chromatography-tandem mass spectrometry bioanalytical method has been developed for the estimation of cycloserine in human plasma, employing cytosine as the internal standard. The extraction of the analyte was facilitated by solid-phase extraction using 100 µL of human plasma. The separation was carried out on a BDS Hypersil C18 (150 × 4.6 mm, 5 µm) column using a mixture of 0.2% formic acid in HPLC-grade water, methanol and acetonitrile (70:15:15, v/v/v) as mobile phase at a flow rate of 1.0 mL/min. The method was linear over the range of 0.20-20 µg/mL with r2 > 0.99. Complete validation of the method was performed as per US Food and Drug Administration guidelines and the results met acceptance criteria. Applying the present method, the clinical pharmacokinetics of cycloserine following oral administration of 250 mg cycloserine was studied under fasting conditions. Assay reproducibility was also verified by incurred sample reanalysis.

High sensitive LC-MS/MS method for estimation of eluxadoline in human plasma and its application to pharmacokinetic study.

A selective, sensitive and high throughput liquid chromatography - tandem mass spectrometry (LC-MS/MS) method was developed and validated for estimation of eluxadoline in human plasma. Plasma samples of analyte with internal standard (eluxadoline13CD3) were extracted using solid phase extraction on Orochem Panthera Deluxe cartridges. Chromatographic separation was performed on Ace Phenyl column (150 × 4.6 mm, 5 µm), using a mixture of buffer (2 mM ammonium acetate in 0.01% formic acid), acetonitrile and methanol (20:70:10, v/v/v) as mobile phase at a flow rate of 0.8 mL/min. The run time of analyte was 4.0 min. Tandem mass spectrometry, operating in positive ionization and multiple reaction monitoring modes was used for detection of analyte and internal standard. The method was established with a linear dynamic range of 25.0-5000 pg/mL for eluxadoline using 300 µL human plasma. The sample preparation procedure was consistent and reproducible (accuracy, 96.2-106.1%; precision (%CV), 0.8-6.6%), preventing the ex vivo hydrolysis of acyl glucuronide metabolite of eluxadoline to parent drug. The method was applied successfully to a clinical pharmacokinetic study in six healthy South Indian male subjects under fed conditions and the results were authenticated by incurred sample reanalysis.