Abstract: The present invention relates to a new oral pharmaceutical composition having an improved release of the therapeutically active compound present therein, in the lower part of the gastro-intestinal duct having a pH exceeding 4.5, comprising as a core a therapeutically active compound in the form of a weak base, or a weak acid, on which core there is applied a first, inner layer of a diffusion membrane in the form of ethyl cellulose, and/or a copolymer of polyethyl methacrylate-methyl methacrylate-trimethylammonium ethyl methacrylate chloride, and thereabove a second layer is applied of at least one anionic polymer and/or fatty acid having a pk.sub.a of 4.5 to 7.The invention further relates to a process for the preparation of said composition, a pharmaceutical composition containing said composition, and a method for the treatment using such a composition.