Abstract: The present invention is directed a pharmaceutical composition which can be administered orally, allowing for the controlled release of at least one active substance. The composition includes at least one active substance, between 5 and 60% by weight, relative to the total weight of the composition, of at least one excipient, selected from the group consisting of inert matrices, hydrophilic matrices, lipid matrices, mixtures of inert matrices and of lipid matrices, and mixtures of hydrophilic matrices and of inert matrices, with the exception of mixtures comprising a polyacrylic acid and at least one hydrophilic matrix of the cellulose type; and between and 14.3% by weight, relative to the total weight of the composition, of at least one alkalinizing agent soluble in an aqueous phase under physiological pH conditions, selected from the group consisting of alkali or alkaline-earth metal hydroxides, carbonates, bicarbonates, phosphates, sodium borate and basic salts of organic acids.