Development and validation of analytical method for the determination of radotinib in human plasma using liquid chromatography-tandem mass spectrometry

This study describes the development of an analytical method to determine radotinib levels in human plasma using high performance liquid chromatography (HPLC) coupled with triple quadrupole tandem mass spectrometry (MS/MS) for pharmacokinetic application. Plasma samples were sequentially processed by liquid-liquid extraction using methyl tert-butyl ether, evaporation, and reconstitution. Analytes were separated and analyzed using HPLC-MS/MS in selected reaction monitoring mode, monitoring the specific transitions of m/z 531 to 290 for radotinib and m/z 409 to 238 for amlodipine (internal standard). The HPLC-MS/MS analytical method was validated with respect to selectivity, linearity, sensitivity, accuracy, precision, recovery, and stability. Calibration curves were linear over a concentration range 5–3,000 ng/mL with correlation coefficients (r) > 0.998. The lower limit of quantification for radotinib in plasma was 5 ng/mL. The accuracy and precision of the analytical method were acceptable within 15% at all quality control levels. This method was suitable to determine radotinib levels in human plasma because of its simplicity, selectivity, precision, and accuracy.

Influence of Simvastatin on Pharmacokinetics/Pharmacodynamics of Aspirin after Oral Co-administration in Healthy Volunteers

BACKGROUND: Both aspirin and simvastatin are prescribed as treatments or prevention of cardiovascular diseases. The aim of this study was to investigate the influence of simvastatin on pharmacokinetics and pharmacodynamics of aspirin after oral co-administration in healthy subjects. METHODS: Subjects were orally administered aspirin 100 mg for 7 days followed by co-administration of aspirin 100 mg and simvastatin 40 mg for 7 days once daily. A series of blood samples were collected before and till 24hours after drug administration on Day 1 (single-dose of aspirin), Day 7 (multiple-dose of aspirin) and Day 14 (multiple-dose of aspirin and simvastatin). The effects of simvastatin on pharmacokinetics of acetylsalicylic acid and salicylic acid were assessed with the 90 % confidence intervals (CIs) of thegeometric mean ratios (GMRs) of Day 14 over Day 7 for maximum plasma concentration (Cmax) and the area under the concentration-time curve (AUC0-24). Pharmacodynamics was assessed with maximal changes of platelet aggregation from baseline. RESULTS: Twenty-fourhealthy men aged 20 to 36 years were enrolled and 23 of them completed the study. GMRs (90 % CIs) of Cmax and AUC0-24 for acetylsalicylic acid were 1.21 (1.04 - 1.42) and 1.28 (1.19 - 1.38), respectively. For salicylic acid, GMRs of Cmax and AUC0-24 were 0.96 (0.91 - 1.00) and 1.00 (0.97 - 1.04), respectively. Maximal changes of platelet aggregation on Day 7 and Day 14 from baseline were not significantly different (p=0.41); 87.5 +/- 8.8 % and 87.3 +/- 9.2 %, respectively. CONCLUSION: Coadministration of simvastatin slightly increased the systemic exposure of acetylsalicylic acid with no changes of systemic exposure of salicylic acid or inhibition of platelet aggregation.