STUDY OF A COMPLEXATION PROCESS BETWEEN NALTREXONE AND EUDRAGIT(R) L AS AN ORAL CONTROLLED-RELEASE SYSTEM

Polymeric complexes based on the interaction between Eudragit(R) L and naltrexone hydrochloride were elaborated. A preformulation study of t he drug was designed to address the following points: (a) the developm ent of two alternative methods (high performance liquid chromatography (HPLC) and UV spectrophotometry) for the analysis and quantifying of naltrexone; (b) the determination of the aqueous solubility of naltrex one hydrochloride; and (c) the characterization of naltrexone hydrochl oride from the following points of view: morphological (scanning elect ronic microscopy, SEM), thermal (differential scanning calorimetry, DS C and hot stage-microscopy, HSM) and spectroscopical (H-1- and C-13-nu clear magnetic resonance, NMR). Furthermore, some of these thechniques were used for the physical and chemical characterization of naltrexon e polymeric complexes. An interaction by means of hydrogen bonds betwe en the polymer and naltrexone was demonstrated using NMR spectroscopic techniques. The in vitro release of naltrexone-Eudragit(R) L complex using a pH gradient technique was studied. A significant reduction in the release rate of drug from the complex used as naltrexone controlle d release system as well as a very high efficiency in the dissolution process have been found. (C) 1997 Elsevier Science B.V.