A simple and high-resolution HPLC-PDA method for simultaneous quantification of local anesthetics in in vitro buccal permeation enhancement studies.

A simple, isocratic, high-resolution and prompt HPLC-PDA method was developed and validated for the simultaneous quantification of prilocaine (PCL) and lidocaine (LCL) hydrochlorides in in vitro buccal iontophoresis-driven permeation studies. A reversed-phase C18 column (250 mm x 4.6 mm, 3µm, 110Å) was used for the chromatographic separation. The mobile phase contained acetonitrile: 0.1M sodium phosphate buffer, pH 7.0 (1:1, v/v), plus 0.05% (v/v) diethylamine. The isocratic flow rate was set at 1 mL/min and the detection wavelength was 203 nm. PCL and LCL eluted in 8.9 min and 13 min, respectively, and the system suitability parameters varied within an acceptable range. The method was selective, sensitive, precise, accurate and robust, producing a linear plot at the concentration range of 0.25 to 10 µg/mL. The application of this method was demonstrated by a significant enhancement of the permeation of PCL and LCL with the application of iontophoresis (1 mA/cm(2) per 1 h) through isolated porcine esophageal epithelium. The amount of the drug retained in the epithelium also increased with the application of an electrical current. Copyright © 2015 John Wiley & Sons, Ltd.

Simultaneous determination of dipyrone metabolites in rat hypothalamus, cerebrospinal fluid and plasma samples by LC-MS/MS.

BACKGROUND: After oral administration dipyrone is rapidly hydrolyzed to 4-methylaminoantipyrine, which is absorbed and further metabolized to 4-formylaminoantipyrine and to 4-aminoantipyrine, which is acetylated by a polymorphic N-acetyltransferase system to 4-acetylaminoantipyrine. To evaluate the presence of dipyrone metabolites in different rat matrices after intraperitoneal administration, an analytical method was developed and validated. METHODOLOGY: The four main dipyrone metabolites were extracted from plasma, cerebrospinal fluid and hypothalamus samples by LLE prior to LC-MS/MS. RESULTS: Standard calibration graphs for all metabolites were linear (r > 0.99). The intra- and inter-day precision and accuracy values were both inferior to 15%. CONCLUSION: This method is simple and specific for studying dipyrone metabolites after intraperitoneal administration.

Capillary electrophoresis method for the determination of isradipine enantiomers: stability studies and pharmaceutical formulation analysis.

A simple enantioselective method based on CE using CD as chiral selector was developed and validated for the determination of isradipine (IRD) enantiomers in a pharmaceutical formulation and for the determination of IRD enantiomers in degradation studies. After optimization, the best results were obtained using 15 mM borate buffer at pH 9.3 and sulfobutyl ether-ß-cyclodextrin (2.5%, w/v) as chiral selector. The applied voltage was +30 kV, and the sample injection was performed in the hydrodynamic mode. All analyses were carried out in a fused-silica uncoated capillary with an id of 50 µm and total length of 60.0 cm. Under these conditions, a complete separation between IRD enantiomers was achieved in less than 7 min. Linearity was obtained in the range 50-300 µg/mL for both enantiomers (r≥0.9978). The RSD (%) and relative errors (%) obtained in precision and accuracy studies (intra-day and inter-day) were lower than 5%. Therefore, this method was found to be appropriate for controlling pharmaceutical formulations containing IRD enantiomers and the assay was considered to be stability indicating. The drug was subjected to oxidation, hydrolysis and photolysis. In all stress conditions the drug presented considerable degradation when compared with a fresh sample (zero time).

Enantioselective fungal biotransformation of risperidone in liquid culture medium by capillary electrophoresis and hollow fiber liquid-phase microextraction.

Knowing that microbial transformations of compounds play vital roles in the preparation of new derivatives with biological activities, risperidone and its chiral metabolites were determined by capillary electrophoresis and hollow fiber liquid-phase microextraction after a fungal biotransformation study in liquid culture medium. The analytes were extracted from 1 mL liquid culture medium into 1-octanol impregnated in the pores of the hollow fiber, and into an acid acceptor solution inside the polypropylene hollow fiber. The electrophoretic separations were carried out in 100 mmol/L sodium phosphate buffer pH 3.0 containing 2.0% w/v sulfated-α-CD and carboxymethyl-ß-CD 0.5% w/v with a constant voltage of -10 kV. The method was linear over the concentration range of 100-5000 ng/mL for risperidone and 50-5000 ng/mL for each metabolite enantiomer. Within-day and between-day assay precisions and accuracies for all the analytes were studied at three concentration levels, and the values of relative standard deviation and relative error were lower than 15%. The developed method was applied in a pilot biotransformation study employing risperidone as the substrate and the filamentous fungus Mucor rouxii. This study showed that the filamentous fungus was able to metabolize risperidone enantioselectively into its chiral active metabolite, (-)-9-hydroxyrisperidone.

Capillary electrophoresis method for plasmatic determination of imatinib mesylate in chronic myeloid leukemia patients.

Imatinib (IMAT) is a tyrosine kinase inhibitor that has been used for the treatment of chronic myeloid leukemia (CML). Despite the efficacy of IMAT therapy, some cases of treatment resistance have been described in CML. Developing a plasma method is important since there are several studies that provided a higher correlation between IMAT plasma concentration and response to treatment. Therefore, in this investigation we validated a method by CE as an alternative, new, simple and fast electrophoretic method for IMAT determination in human plasma. The analysis was performed using a fused silica capillary (50 µm id×46.5 cm total length, 38.0 cm effective length); 50 mmol/L sodium phosphate buffer, pH 2.5, as BGE; hydrodynamic injection time of 20 s (50 mbar); voltage of 30 kV; capillary temperature of 35°C and detection at 200 nm. Plasma samples pre-treatment involved liquid-liquid extraction with methyl-tert-butyl ether as the extracting solvent. The method was linear from 0.125 to 5.00 µg/mL. The LOQ was 0.125 µg/mL. Mean absolute recovery of IMAT was 67%. The method showed to be precise and accurate with RSD and relative error values lower than 15%. Furthermore, the application of the method was performed in the analysis of plasma samples from CML patients undergoing treatment with IMAT.