RESUMO
Exposure of dry powder forms of the drugs nitrendipine, nifedipine, felodipine, and nimodipine to gamma-radiation results in the formation of free radicals detected by electron paramagnetic resonance (EPR) spectroscopy. The four structurally related drugs show qualitatively identical EPR spectral features in terms of g-values, the qualitative descriptive parameter. These radicals are very stable, surviving long periods of time in excess of 9 months and possibly beyond conventional shelf-life of the drugs. The residual radical population is high enough to be detectable after long storage. Administration of such radiation-treated drugs may present patients with quantities of free radicals and possibilities of secondary cell damage.
Assuntos
Bloqueadores dos Canais de Cálcio/efeitos da radiação , Espectroscopia de Ressonância de Spin Eletrônica/métodos , Relação Dose-Resposta à Radiação , Felodipino/efeitos da radiação , Radicais Livres/efeitos da radiação , Raios gama , Nifedipino/efeitos da radiação , Nimodipina/efeitos da radiação , Nitrendipino/efeitos da radiaçãoRESUMO
Decomposition of nifedipine in Adalat tabl. and Cordafen drops and nitrendipine in Nitrendipine tabl. preparations under influence of UV radiation operation and temperature of 50 degrees C was tested. Chromatographic methods of TLC and HPCL and spectrophotometry were used for evaluation of the decomposition processes.
Assuntos
Bloqueadores dos Canais de Cálcio/química , Nifedipino/química , Nitrendipino/química , Bloqueadores dos Canais de Cálcio/efeitos da radiação , Cromatografia Líquida de Alta Pressão , Cromatografia em Camada Fina , Estabilidade de Medicamentos , Nifedipino/efeitos da radiação , Nitrendipino/efeitos da radiação , Espectrofotometria Ultravioleta , Raios UltravioletaRESUMO
A new nitrendipine derivative [ethyl-2-(1-piperidino)ethyl-1,4-dihydro-2,6-dimethyl-4-(3-nitrophenyl)- 3,5-pyridine dicarboxylate hydrochloride;1] was assayed in plasma by high-performance liquid chromatography. After deproteinization and extraction, 1 and nitrendipine, as the external standard, were separated by ion-pair chromatography and measured by UV detection (254 nm). The method is rapid and specific: the limit of sensitivity of the assay was 5 ng/mL and the concentration range was linear between 5 and 2000 ng/mL. In vitro studies showed that, in contrast to nifedipine and nicardipine, 1 and nitrendipine were stable when exposed to light for at least 4 h. Pharmacokinetic parameters obtained in three beagle dogs after oral and intravenous administration are reported. Comparison with a nicardipine pharmacokinetic study showed similar results for the distribution and elimination characteristics of these two drugs.