Simultaneous determination of methotrexate, dasatinib and its active metabolite N- deshydroxyethyl dasatinib in rat plasma by LC-MS/MS: method validation and application to pharmacokinetic study.

Dasatinib is a multi-kinase inhibitor that potently inhibits Bcr-Abl, Src family and platelet-derived growth factor receptor kinases. Methotrexate is an antimetabolite and antifolate drug. Clinical trials utilizing a combination of dasatinib and methotrexate in patients with Philadelphia chromosome positive and/or Bcr-Abl positive acute lymphoblastic leukemia are currently ongoing. A need therefore exists to develop a sensitive analytical method for determination of dasatinib and methotrexate in plasma.To estimate methotrexate, dasatinib and its active metabolite N-deshydroxyethyl dasatinib simultaneously using liquid chromatography-electrospray ionization tandem mass spectrometry (HPLC-ESI-MS/MS) in Wistar rat plasma.The analytes were extracted by using liquid-liquid extraction procedure and separated on a reverse phase C18 column (50 mm×3 mm i.d., 4.6 µ) using methanol: 2 mM ammonium acetate buffer, pH 4.0 as mobile phase at a flow rate 1 mL/min in gradient mode. Selective reaction monitoring was performed using the transitions m/z 455.0>175.0, 488.1 > 401.0, 444.26>401.0, and 271.1>- 155.0 to quantify methotrexate, dasatinib, N-deshydroxyethyl dasatinib and tolbutamide respectively.The method was validated over the concentration range of 1-1 000 ng/mL and the lower limit of quantitation was 1 ng/mL. The recoveries from spiked control samples were > 79% for all analytes and internal standard Intra- and Interday accuracy and precision of validated method were within the acceptable limits of < 15% at all concentration.The quantitation method was successfully applied for simultaneous estimation of methotrexate, dasatinib and N- deshydroxyethyl dasatinib in a pharmacokinetic study in Wistar rats.

Effect of pentoxifylline on the pharmacokinetics of rosiglitazone in Wistar rats.

The aim of this study was to investigate the effect of pentoxifylline (PTX), an antiplatelet agent, on the pharmacokinetics of rosiglitazone (RSG) in rats. Pharmacokinetic parameters of RSG were determined in rats after oral administration (3 mg/kg/day) in the presence and absence of PTX (10 mg/kg) 3 times daily. Compared to control animals, rats pretreated with PTX for 7 days had a decrease in RSG peak plasma concentration (Cmax) of 19% with no change in the values of the area under the concentration-time curve (AUC). Alternatively, rats coadministered single-dose PTX did not show any differences from control with regard to RSG Cmax and AUC parameters. The time to peak concentration (tmax) of RSG was significantly increased in rats pretreated with PTX under both single- and multiple-dose conditions, whereas the elimination half-life (t1/2) of RSG was increased only with multiple-dose PTX pretreatment. In conclusion, the presence of PTX was found to cause a slight decrease in the oral exposure of RSG in rats. Concurrent use of PTX with RSG therefore needs to be appropriately evaluated for proper dose adjustments in humans.