Kálmán Róna

High-performance liquid chromatographic method with coulometric detection for the determination of buspirone in human plasma by means of a column-switching technique

A reversed-phase high-performance liquid chromatographic method with electrochemical detection has been developed for the determination of buspirone from human plasma. The separation was carried out by using a Supelcosil ABZ+ plus C18 reversed-phase column and 0.05 M potassium dihydrogenphosphate (pH 6.5)-acetonitrile (7:3, v/v) as the mobile phase. The compounds were detected by coulometry. Buspirone and the internal standard were extracted from the human plasma using Bond-Elut C18 solid-phase extraction cartridges. Following removal of the the highly lipophilic plasma components we applied a column-switching technique which reduced the duration of HPLC measurement from 60 min to 15 min. The limit of quantitation was found to be 100 pg/ml plasma.

Liquid chromatographic method for the determination of ticlopidine in human plasma

A simple high-performance liquid chromatographic method for determination of ticlopidine in human plasma using ultra violet detection was developed. The separation of the investigated compound and internal standard was achieved on a C18 BD column with a 0.01 M potassium dihydrogen phosphate buffer (pH 4)-acetonitrile-methanol (20:40:40, v/v) mobile phase. The detection was performed at 215 nm. The compounds were isolated from plasma by Bond Elut C18 solid-phase extraction, the mean absolute recovery was 84.9%. The limit of quantitation was 10 ng ml(-1), the limit of detection was 5 ng ml(-1). The bioanalytical method was validated with respect to linearity, within- and between-day accuracy and precision. system suitability and stability. All validated parameters were found to be within the internationally required limits. The developed analytical method for ticlopidine was found to be suitable for application in pharmacokinetic studies and human drug monitoring.

Simultaneous determination of nerisopam, a novel anxiolytic agent showing polymorphic metabolism, and its N-acetyl metabolite from human plasma by a validated high-performance liquid chromatographic method

A sensitive reversed-phase high-performance liquid chromatographic method with ultraviolet absorbance detection has been developed to simultaneously determine the concentrations of nerisopam (EGIS-6775) and its N-acetyl metabolite (EGIS-7649) from human plasma. The separation of the investigated compounds and internal standard was achieved on a Nucleosil 7 C(18) column with 2 mM heptanesulphonic acid containing 0.04 M phosphoric acid-acetonitrile-methanol (70:25:5, v/v), pH 2.7 mobile phase. The detection was performed at 385 nm. The compounds were isolated from plasma by Bakerbond C(18) solid-phase extraction. The limit of quantitation was 10 ng/ml plasma for each compound investigated. The assay has been validated with respect to accuracy, precision and system suitability. All validated parameters were found to be within the necessary limits. On the basis of the sensitivity, linearity and validation parameters, the developed analytical method was found to be suitable for the determination of nerisopam and its N-acetyl metabolite from human plasma and for application in pharmacokinetic studies and human drug monitoring. The pharmacokinetic parameters obtained from twelve human volunteers are reported. It was found that nerisopam acetylation is polymorphic: the volunteers with fast or slow acetylator phenotypes produced significantly different plasma concentrations. In slow acetylator phenotypes the concentration of nerisopam was considerably higher in plasma, while the level of its acetyl metabolite was higher in plasma of fast acetylators.

Comparative bioavailability of alpha-methyldopa normal and film tablet formulations after single oral administration in healthy volunteers.

SummaryIn a single dose, randomized, cross-over study, with one week of wash-out period, the relative bioavailability of Dopegyt® tablets containing 250 mg alpha-methyldopa (AMD) and Presinol® film tablets with identical active ingredient content was examined in 24 healthy volunteers.Since technologically two completely different preparations (a film-tablet and a non-film-tablet) having significantly different in vitro dissolution were to be compared, both preparations were compared to a third one, AMD solution (Dopegyt® solution) with 250 mg/50 ml concentration. Plasma concentrations of the drug were measured for 24 hours post-dose, applying HPLC with fluorometric detection. Pharmacokinetic parameters calculated from individual data (AUC0−∞, AUC0−t, Cmax, Cmax/AUC0−∞, tmax) were evaluated statistically. Wilcoxon’s nonparametric test and the four-way variance analysis could not detect any significant difference at the usual a=95% probability level in these pharmacokinetic parameters of the two tablet preparations. For AUC0−∞ at the 90% probability level, the confidence interval was 0.883–1.237 (with an estimated geometric mean of 1.045), for the test/reference ratio of Dopegyt® and Presinol® tablets, thus the two preparations proved to be bioequivalent. The relative bioavailability of Dopegyt® (test preparation) and Presinol® (reference preparation) calculated from the AUC0−∞ values was 116.7±56.7% that also confirmed bioequivalence. The results of all the applied statistical tests suggest that Dopegyt® and Presinol® can be considered as bioequivalent preparations.

Validated liquid chromatographic method for the determination of N-3-(2,2,5,5-tetramethyl-3-pirrolin-3-carboxamidopropylphthalimide hydrochloride), a novel antiarrhythmic agent in human plasma

A simple high-performance liquid chromatographic method with ultraviolet absorbance detection has been developed to determine the concentration of N-3-(2,2,5,5-tetramethyl-3-pirrolin-3-carboxamidopropylphthalim ide hydrochloride; A-2545), a new antiarrhythmic agent from human plasma. Separation of the investigated compound and internal standard was achieved on a Nucleosil 7 C18 column with a 0.01-M potassium dihydrogenphosphate buffer (pH 2.5)-methanol (60:40, v/v) mobile phase. The detection was performed at 220 nm. During the determinations, buspirone served as the internal standard. The compounds were isolated from plasma on a Bakerbond C18 solid-phase extraction cartridge and the mean absolute recovery was 92.9%. The limit of quantitation was found to be 10 ng/ml. The bioanalytical method was validated with respect to linearity, within- and between-day accuracy and precision, system suitability and stability. All validated parameters were found to be within the internationally required limits. The developed analytical method for A-2545 was found to be suitable for application in pharmacokinetic studies and for human drug monitoring.