Development and validation of stability indicating LC-MS/MS Technique for the quantification of tapentadol in biological matrices: Application to bioavailability study in healthy rabbits

An Liquid chromatography tandem mass spectrometry (LC-MS/MS) technique is one of the best analytical methods for thequantification of drugs in biological samples. A stability-indicating analytical technique was developed for the quantitationof tapentadolin biological matrices as tapentadol with short runtime. Developed technique also suitable for bioavailabilitystudies in healthy rabbits. Separation of tapentadol and tapentadol-d3 were achieved from plasma sample with solid-phaseextraction and elution was processed with Luna-C18 (5 μ, 100 mm × 4.6 mm) stationary column with movable phase ratiocomprising 2-mM ammonium acetate buffer (pH-3.6) and acetonitrile in the proportion of 10:90 % V/V. Quantitationwas processed by processing the transitions of tapentadol and tapentadol-d3 at m/z 222.2 → 177.1 and 228.2 → 183.1,respectively, in positive ionization mode. Linearity was performed over the concentration range of 0.121 to 35.637 mg/ml(R2 > 0.99) without matrix effect (2.74%). The inter- and intra-day precision findings were within 8.62% and 11.38%,respectively. Stability data showed that the tapentadol was stable when it exposed to different stability conditions. Thistechnique was effectively applied to bioavailability studies of tapentadol in healthy rabbits

Investigação da influência da velocidade de liberação do fármaco metoprolol a partir da forma farmacêutica sobre seu processo de absorção e de seus enantiômeros / Influence of the input rate of metoprolol on the absorption of its enantiomers

A Agência Nacional de Vigilância Sanitária (ANVISA) não exige a realização de ensaios de bioequivalência utilizando métodos enantiosseletivos de quantificação de fármacos para o registro de medicamentos genéricos ou similares contendo fármacos racêmicos. Porém, existe a possibilidade das diferenças de concentrações plasmáticas dos enantiômeros entre o medicamento referência e os genéricos e/ou similares comercializados no Brasil serem maiores que as estabelecidas pelos limites de bioequivalência. Esse estudo teve a finalidade de investigar a influência da velocidade de liberação do fármaco metoprolol, a partir da forma farmacêutica, sobre o processo de absorção do fármaco total e de seus enantiômeros por meio da avaliação das concentrações plasmáticas de metoprolol total, (S)-metoprolol e (R)-metoprolol, e da relação entre as concentrações dos enantiômeros (S/R) após a administração oral de medicamentos contendo mistura racêmica deste fármaco. Para isso, foi realizado ensaio de biodisponibilidade in vivo, em um grupo de 20 voluntários saudáveis, de acordo com procedimentos éticos estabelecidos internacionalmente. Foram empregados três esquemas de administração do metoprolol, com a finalidade de simular diferentes velocidades de liberação do fármaco a partir da forma farmacêutica, na Fase 1 foi administrado uma dose única de 100 mg de metoprolol em solução, na Fase 2 e Fase 3 essa mesma dose foi particionada em duas e cinco administrações, respectivamente, com intervalo de 30 minutos entre elas. Foram coletadas amostras de sangue, e estas foram analisadas utilizando método convencional e método quiral para quantificação do metoprolol total e seus enantiômeros, respectivamente, utilizando cromatografia líquida de alta eficiência, com detector de fluorescência. Os parâmetros farmacocinéticos de ASC0-t, Cmáx e Tmáx foram utilizados para comparação entre as três velocidades de liberação do fármaco a partir da forma farmacêutica. A análise farmacocinética para o fámaco (R,S) metoprolol e seus enantiômeros e a comparação entre seus parâmetros farmacocinéticos obtidos após administração oral do metoprolol, indicam uma cinética enantioseletiva para o metoprolol, que pode ter ocorrido devido a uma biotransformação pré-sistêmica dose-dependente, ou a uma inibição do metabolismo do (S)-metoprolol pela forma (R)-metoprolol

ANVISA, brazilian regulatory agency for drug products, does not require the use of enantioselective bioanalytical methods in bioequivalence assays of generic and similar drug products containing racemic drugs. Therefore, it is possible that two formulations are bioequivalent based on plasmatic concentration of total drug, but are not bioequivalent on the basis of the comparison of the data of the stereoisomers. The objective of this study was to investigate the influence of the release rate of metoprolol from the dosage form on its absorption process and on its enantiomers' absorption process by measuring plasmatic concentrations of total metoprolol, (S)-metoprolol and (R)-metoprolol after oral administration of drug products containing racemic metoprolol. An in vivo bioavailability study was conducted in a group of 20 healthy volunteers, according to national and international guidelines for biomedical research, in which the administration rate of metoprolol was varied. In Phase 1 a single dose of 100 mg metoprolol was administered in solution, in Phase 2 and Phase 3 the same dose was partitioned into two and five administrations, respectively, with an interval of 30 minutes between them. Blood samples were collected, and these were analyzed using the conventional method and chiral method for quantification of (R,S)-metoprolol and for its enantiomers, using high performance liquid chromatography with fluorescence detection. The pharmacokinetic parameters AUC0-t, Cmax and Tmax were used for comparisons between three different drug release rates. Pharmacokinetic analysis for (R, S) metoprolol and its enantiomers and comparison of their pharmacokinetic parameters obtained after oral administration of metoprolol, to indicate an enantioselective kinetic, which may be due to a biotransformation pre-systemic dose dependent or the inhibition of metabolism of the (S)-form for metoprolol (R)-metoprolol

Bioavailability study of chlorpropamide tablets in healthy volunteers.

Bioavailability study was conducted on 250 mg-chlorpropamide tablets from 10 locally manufactured brands and an innovator one (Diabinese). The results of the tests for quality according to the pharmacopoeia were as follows: weight uniformity of all the brands was in accordance with the USP XXII standard, the content of one of them failed, and disintegration test of one brand failed (BP 1,973 and USP XIX). In addition five brands failed to meet the USP XXII dissolution specification, while only 2 brands failed to meet the BP 1,988 specification. Four brands of chlorpropamide tablets were selected for studying their bioequivalence in 20 Thai healthy male volunteers, receiving orally a half dose of 250 mg, using a cross-over randomized design, one representing the rapid dissolution rate group, the innovator one representing the intermediate dissolution rate group and 2 brands representing the slow rate group (one failed the USP XXII, but met the BP 1,900 dissolution specification (a) and the other failed both USP XXII and BP 1,988 dissolution specification (b). Plasma chlorpropamide levels were determined by a specific high performance liquid chromatographic method. Individual plasma profiles were analysed using PC NONLIN computer program-two compartment open model. There was no significant difference (p > 0.05) with regard to extent and rte of absorption between the brand having the intermediate dissolution rate (the innovator one) and the slow dissolution drug (b), while the brand representing rapid dissolution rate was absorbed more rapidly (p < 0.05). However the absorption rate of the local made product had an higher standard error than that of the innovator, absorption rates did not have any effect on the hypoglycemia, because drug levels in the absorption period were lower that the therapeutic level and steady state. Besides, in testing blood glucose level of volunteers before and after having received orally the 4 brands at different times, it was fond that there was no significant difference (p > 0.05) between the level before taking the drugs and that after 2 hours. There was no significant correlation between the in vivo absorption rate and the dissolution, USP XXII method (p > 0.05). The mean peak chlorpropamide concentration in plasma (half dose taken) was between 14.59 and 16.69 ug/ml, and the half-life (T1/2, e) was between 43.73 and 49.42 hours.