Sustained release preparations, which show suppressed initial release of a physiologically active substance and can release a constant amount of the physiologically active substance over a long period of time, and dispersion vehicle thereof can be obtained by adding a cationic substance or polyols to the outside of a matrix or dispersion vehicle thereof. Thus, sustained release preparations, which show suppressed initial release of a physiologically active substance immediately after the administration and can release a constant amount of the physiologically active substance over a long period of time and dispersion vehicle thereof can be provided.
