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.

Redefining Statin Dosage Post-Gastric Bypass: Insights from a Population Pharmacokinetics-Pharmacodynamics Link Approach.

Roux-en-Y gastric bypass (RYGB) involves creating a small stomach pouch, bypassing part of the small intestine, and rerouting the digestive tract. These alterations can potentially change the drug exposure and response. Our primary aim was to assess the impact of RYGB on the pharmacokinetics of simvastatin lactone (SV) and its active metabolite, simvastatin hydroxy acid (SVA). Ultimately, we aimed to optimize dosing for this understudied population by employing a population pharmacokinetic-pharmacodynamic link approach. The study comprised patients who had undergone RYGB surgery and individuals without a previous history of RYGB. All participants received a single oral dose of simvastatin. Plasma concentration data were analyzed with a nonlinear mixed-effect modeling approach. A parent-metabolite model with first-order absorption, 2-compartments for SV and 1-compartment for SVA, linear elimination, and enterohepatic circulation best described the data. The model was linked to the turnover pharmacodynamic model to describe the SVA inhibition on LDL-cholesterol production. Our simulations indicated that following RYGB surgery, the exposure to SV and SVA decreased by 40%. Consequently, for low-intensity statin patients, we recommend increasing the dose from 10 to 20 mg in post-RYGB patients to maintain a comparable response to that of non-operated subjects. Moderate-intensity statin patients should require increasing doses to 40 or 60 mg or the addition of a non-statin medication to achieve similar therapeutic outcomes. In conclusion, individuals post-RYGB exhibit diminished exposure to SV and may benefit from increasing the dose or adjunctive therapy with non-statin drugs to attain equivalent responses and mitigate potential adverse events.

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).

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.

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.

Omeprazole Absorption and Fasting Gastrinemia After Roux-en-Y Gastric Bypass.

PURPOSE: Roux-en-Y gastric bypass (RYGB) is one of the bariatric surgeries most frequently performed worldwide. Since this operation may predispose to the formation of peptic ulcer of the gastrojejunal anastomosis, the use of proton pump inhibitors (PPI) is recommended during the first postoperative year. However, so far, there is no detailed knowledge about the absorption of this medication during the immediate postoperative period and consequently about its effectiveness in blocking acid secretion. The objective was to assess the possible endoscopic peptic changes, the absorption of omeprazole (OME), and the status of fasting gastrinemia before and after RYGB operation. MATERIALS AND METHODS: OME absorption, the production of its metabolites omeprazole sulfone (OMES) and 5-hydroxyomeprazole (HOME), and basal (fasting) gastrinemia were determined in patients submitted to RYGB before and 2 months after the operation. Upper digestive endoscopy (UDE) was also performed before and 6 months after the operation. RESULTS: Twenty patients were studied. Preoperatively, all these patients had some peptic changes and 55% tested positive for Helicobacter pylori. Six months after surgery, ten patients still showed endoscopic changes and one patient tested positive for H. pylori. During the postoperative period, there was a reduction of OME absorption and of the production of its metabolites 90 min after administration of the drug, and reduction of serum gastrin levels. CONCLUSION: The standard OME dose (40 mg) administered after bariatric surgery is insufficient to achieve serum levels that can effectively block the production of hydrochloric acid, permitting the formation of peptic injuries in many patients.

Correction to: Omeprazole Absorption and Fasting Gastrinemia After Roux-en-Y Gastric Bypass.

Larissa Alves dos Reis Dias wasmistakenly included in the 13 acknowledgment section of this article, and was mistakenly.

Self-Assembled Nanospheres for Encapsulation and Aerosolization of Rifampicin.

Rifampicin (RIF) is a benchmark drug for treatment of tuberculosis, but poor bioavailability, prolonged treatment, and pill burden have been linked to therapeutic failure and the development of multidrug resistant strains. To overcome these limitations, this study investigated a method of rifampicin nanoencapsulation and aerosol delivery using a commercial, hand-held nebulizer modified with a nitrogen stream.

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.

Microparticles as a strategy for low-molecular-weight heparin delivery.

The aims of this work were preparation and physical-chemical characterization of a microparticulate release system for delivery of enoxaparin sodium (ENX), a low-molecular-weight heparin, as a potential vehicle for optimization of deep venous thrombosis therapy. Microparticles (MPs) containing ENX were prepared from polylactide-co-glycolic acid [PLGA; (50:50)] by a double emulsification/solvent evaporation method. The preparation parameters, such as proportion ENX/PLGA, surfactant concentration, type, time, and speed of stirring, were evaluated. The encapsulation efficiency and yield process were determined and optimized, and the in vitro release profile was analysed at 35 days. The MPs showed a spherical shape with smooth and regular surfaces. The size distribution showed a unimodal profile with an average size of 2.0 ± 0.9 µ m. The low encapsulation efficiency (<30%), characteristic of hydrophilic macromolecules was improved, reaching 50.2% with a procedure yield of 71.3%. The in vitro profile of ENX release from the MPs was evaluated and showed pseudo-zero-order kinetics. This indicated that diffusion was the main drug release mechanism.