Abstract: The invention relates to compositions in the form of microcapsules or implants comprising a biodegradable polymeric or copolymeric excipient or a mixture of such excipients with an inherent viscosity of between 0.5 dl/g and 1.6 dl/g in CHCl3, and one active substance or a mixture of active substances, it being possible for said microcapsules or implants to release the active substance or mixture of active substances over a prolonged period of up to three months or more. These compositions may also comprise an active principle having a high specific surface area.