The present invention relates to novel pharmaceutical formulations based on aqueous colloidal suspensions for the prolonged release of one or more active principles, and to the applications, especially therapeutic applications, of these formulations. Formulations may include an aqueous colloidal suspension of low viscosity based on micrometric particles of a water-soluble, biodegradable, amphiphilic polymer carrying hydrophobic groups and ionizable hydrophilic groups that are at least partially ionized, said particles being capable of associating spontaneously and non-covalently with an active principle, at pH=7.0, under isotonic conditions. This suspension contains multivalent ions of opposite polarity to that of the hydrophilic groups, the ratio r, defined by the formula r=n×([IM]/[GI]), where n is the valency of said multivalent ions, [IM] is the molar concentration of multivalent ions, [GI] is the molar concentration of ionizable groups GI, being between 0.3 and 10.
