RESUMEN
A versatile oral controlled release system for the simultaneous delivery of levodopa methyl ester and carbidopa, consisting of a three-layer matrix tablet, has been studied and developed. Each individual layer of the matrix exhibited a different release mechanism, i.e. the first layer was swellable (S), the second one was erodible (E) and the third one was disintegrating (D). The three layers have been assembled in the monolithic matrix in different relative positions. It was found that in the monolith the three layers could interact, producing in vitro release profiles depending on their relative position. The monoliths having the configurations DSE and SDE were administered to human volunteers in order to determine the plasma profiles. The pharmacokinetic data showed a significant difference between the early time plasma curves: the monolith DSE, having the fast release profile, gave rise to a rapid appearance of a high levodopa plasma level, whereas the slower releasing monolith SDE produced a smoothed plasma concentration profile.
Asunto(s)
Antiparkinsonianos/farmacocinética , Carbidopa/farmacocinética , Sistemas de Liberación de Medicamentos/métodos , Levodopa/análogos & derivados , Levodopa/farmacocinética , Administración Oral , Antiparkinsonianos/administración & dosificación , Antiparkinsonianos/sangre , Disponibilidad Biológica , Carbidopa/administración & dosificación , Carbidopa/sangre , Química Farmacéutica , Estudios Cruzados , Humanos , Levodopa/administración & dosificación , Levodopa/sangre , Proyectos Piloto , Comprimidos RecubiertosRESUMEN
A sensitive and selective ion-pair high-performance liquid chromatographic method for the determination of 7,7'-carbonylbis[imino-N-methyl-4, 2-pyrrolecarbonylimino(N-methyl-4,2-pyrrole)carbonylimino]¿- bis(1,3-naphthalenedisulphonic acid), tetrasodium salt in monkey plasma has been developed. The compound and internal standard (bromphenol blue) were extracted from plasma samples were methylene chloride (twice) after deproteination with acetonitrile and addition of the ion-pairing agent (tetrabutylammonium hydroxide). The combined organic phases were dried, the residue dissolved in the mobile phase and then analysed by reversed-phase ion-pair liquid chromatography under isocratic conditions. The HPLC analysis time was about 20 min. Quantitation was achieved by UV detection at 323 nm. The linearity, precision and accuracy of the method were evaluated. The limit of quantitation was 0.3 microgram/ml plasma. No interference from blank monkey, mouse, rat, dog and human plasma was observed. The suitability of the method for in vivo samples was checked by analysis of plasma samples drawn from three male cynomolgus monkeys that had received a 20 mg/kg single i.v. dose of the test compound.