A method for preparing a stable composition comprising a benzimidazole derivative selected from the group consisting of omeprazole, pantoprazole, lansoprazole, leminoprazole, perprazole, rabeprazole, and pharmaceutically acceptable salts thereof, the method comprising: applying a solution or dispersion comprising a neutralized hydroxypropylmethylcellulose acetate succinate (HPMCAS) polymer obtained by neutralizing the HPMCAS with ammonium hydroxide and monoethanolamine； wherein the pH of the solution or dispersion is 7-9, to a substrate comprising the benzimidazole derivative to form a single coating layer on said substrate without an intermediate layer between said substrate and said enteric coating, in which a solution or dispersion prepared from the coating layer of the stable composition has a pH in the range of about 4.5 to about 6.5 as measured in 30 ml of distilled water at 20-25 ° C, and in which said stable composition comprises less than about 500 parts per million residual ammonium hydroxide with respect to the total weight of the composition.Un método para preparar una composición estable que comprende un derivado de bencimidazol seleccionado del grupo que consiste en omeprazol, pantoprazol, lansoprazol, leminoprazol, perprazol, rabeprazol, y sales farmacéuticamente aceptables de los mismos, comprendiendo el método: aplicar una disolución o dispersión que comprende un polímero de acetato-succinato de hidroxipropilmetilcelulosa (HPMCAS) neutralizado obtenido neutralizando el HPMCAS con hidróxido de amonio y monoetanolamina； en el que el pH de la disolución o dispersión es 7 - 9, a un sustrato que comprende el derivado de bencimidazol para formar una única capa de recubrimiento sobre dicho sustrato sin una capa intermedia entre dicho sustrato y dicho recubrimiento entérico, en el que una disolución o dispersión preparada a partir de la capa de recubrimiento de la composición estable tiene un pH en el intervalo de aproximadamente 4,5 a aproximadamente 6,5 c
