Synchronous LC-MS/MS determination of pantoprazole and amitriptyline in rabbit plasma: application to comparative in vivo pharmacokinetic study of novel formulated effervescent granules with its marketed tablet dosage form.

In the present study the bioavailability and pharmacokinetics properties of pantoprazole (proton pump inhibitor)/amitriptyline (tricyclic antidepressant) in novel formulated effervescent granules was estimated in rabbit plasma using a validated, selective and rapid LC-MS/MS method. Separation and detection of pantoprazole, amitriptyline and internal standards namely omeprazole and dothiepin, respectively, were achieved at ambient column temperature on C18. Acetonitrile: 4mM ammonium acetate solution (comprising 0.05 % formic acid) (40:60, v/v) was used as mobile phase and the flow rate of 0.6 mLmin-1 was applied. Liquid-liquid extraction technique with diethyl ether: dichloromethane (70:30, v/v) was used to extract the cited drugs from rabbit plasma. Multiple reactions monitoring (MRM) in the positive ionization mode was carried out for quantification. The method was validated over linear concentration range of 0.01-4µgmL-1 and 0.001-0.1 µgmL-1 for Pan and Ami respectively, with regression coefficient (r2) ≥ 0.9961. The intra- and inter-run precisions (%CV) were ≤4.03. The extraction recoveries were in the range of 95.92%-100.24 %. Pan and Ami were stable during three freeze-thaw cycle and post-preparative stability. The work also aimed to formulate immediate release novel effervescent granules by melt granulation technique. Nine formulae were assessed by validated dissolution test for their micrometric properties and dissolution profile. Experimental design was applied to select formula that fulfilled the desired criteria of optimum release of pantoprazole and amitriptyline with optimum micrometric properties for the study. A single period randomized open-label parallel design was applied on Chancellor's rabbit. The selected formula showed superior pharmacokinetic parameters for pantoprazole and amitriptyline than that of marketed products.

Venlafaxine Determination in Pharmaceutical Formulation and Serum by Ion-Selective Electrodes.

BACKGROUND: The application of an ion selective technique for the determination of analyte concentrations is considered one of the most economical techniques for quality control purposes. OBJECTIVE: To elaborate and investigate the construction and general performance characteristics of potentiometric PVC membrane sensors for venlafaxine cation (Ven+). METHOD: The sensors are based on the use of the ion association complexes of the venlafaxine cation with phosphotungstate (PT) and silicotungstate (ST) counter anions as ion exchange sites in the plasticized PVC matrix. They are characterized by potentiometric and conductimetric measurements, performed under various conditions. RESULTS: The electrodes showed a fast (response time around 15 s), stable (life span 45 days) and linear (r2 0.995) response for venlafaxine over the concentration range of 5x10-5 - 1x10-2 M venlafaxine hydrochloride. The solubility product of the ion pair and the formation of the precipitation reaction leading to the ion pair, were determined conductimetrically. The electrodes were found to be very selective, precise (RSD < 1%) and applicable to the potentiometric determination of venlafaxine hydrochloride in pure solutions or in pharmaceutical preparation and in biological fluid (serum), without any interference. Validation of the method shows the suitability of the proposed electrodes for use in the quality assessment of venlafaxine hydrochloride. CONCLUSION: Using only a pH meter in combination with the selective electrodes, drug substance or drug product could be determined accurately in a few seconds. In addition, the in-house made electrodes were tested to monitor venlafaxine in serum. Acceptable results were achieved using the standard addition technique.

Determination of Febuxostat in Human Plasma Using RP-LC-UV Method.

A simple and sensitive bioanalytical high-performance liquid chromatographic method with ultraviolet detection was developed and validated for the quantification of febuxostat (FEB) in human plasma. Ketoprofen was used as an internal standard. The analytes were extracted from human plasma samples by precipitation with acetonitrile. The reconstituted samples were chromatographed on C18 Bondapack 10 µm, 250 × 4.6 mm, Waters Column (Ireland) by using a mixture of acetonitrile and 0.5% aqueous phosphoric acid (pH 3) (52 : 48, v/v) as the mobile phase. The chromatographic separation was isocratically performed at room temperature at a flow rate of 1.0 mL/min with UV detection at 315 nm. The method exhibited a linear dynamic range over 0.05-5.00 µg/mL FEB in human plasma. The lower limit of quantification was 0.05 µg/mL. The results of the intra- and interday precision and accuracy studies were within the acceptable limits. The validated method was successfully applied for the determination of FEB in human plasma samples for application in bioequivalence studies.

Simultaneous determination of chlordiazepoxide and selected antidepressants using CZE.

A simple CE method was developed and validated for the simultaneous determination of chlordiazepoxide (CHL), amitriptyline, and nortriptyline (mixture I) or the determination of CHL and imipramine (mixture II) using the same BGE. Sertraline and amitriptyline were used as internal standards for the first and second mixtures, respectively. The method allows amitriptyline to be completely separated from its impurity and main metabolite nortriptyline, which can be quantified from 0.2 µg/mL. The separation was achieved using 20 mM potassium phosphate buffer pH 5 containing 12 mM ß-cyclodextrin and 1 mM carboxymethyl-ß-cyclodextrin. UV detection was performed at 200 nm and a voltage of 15 kV was applied on an uncoated fused-silica capillary at 25°C. These experimental conditions allowed separation of the compounds to be obtained in 7 min. Calibration graphs proved the linearity up to 40 µg/mL for CHL, up to 100 µg/mL for amitriptyline and imipramine, and up to 5 µg/mL for nortriptyline. The accuracy and precision of the method have been determined by analyzing synthetic mixtures and pharmaceutical formulations. The analytical results were quite good in all cases indicating that the method was linear, sensitive, precise, accurate, and selective for both mixtures.

Simultaneous determination of chlorzoxazone and ketoprofen in binary mixtures and in ternary mixtures containing the chlorzoxazone degradation product by reversed-phase liquid chromatography.

New, simple, rapid, and precise reversed-phase high-performance liquid chromatographic (LC) methods were developed for the simultaneous determination of chlorzoxazone (CH) and ketoprofen (KT) in binary mixtures and in ternary mixtures containing the CH degradation product, 2-amino-4-chlorophenol (CD). The analytes were separated by LC on a Lichrosphere 60 C18 column (250 x 4 mm, 5 microm). The mobile phases, methanol-water (40:60, v/v) at 1 mL/min and methanol-0.05% phosphoric acid (60:40, v/v, pH 2.81) at 1.5 mL/min, satisfactorily resolved the binary and ternary mixtures, respectively. The UV detector was operated at 280 nm for the determination of CH and at 254 nm for the determination of KT and CD. Linearity, accuracy, and precision were found to be acceptable over the concentration ranges of 20-240 and 5-60 microg/mL for CH and KT, respectively, in the binary mixtures and 50-300, 10-60, and 20-160 microg/mL for CH, KT, and CD, respectively, in the ternary mixtures. The optimized methods proved to be specific, robust, and accurate for the quality control of CH and KT in pharmaceutical preparations.