The present invention is directed to compositions for injectable in-situ forming biodegradable implants for extended release that can be used to deliver an antipsychotic drug such as risperidone and to provide therapeutic plasma levels thereof from the first day. The composition is an injectable depot composition, comprising a drug which is risperidone and/or 9-OH-risperidone at least one biocompatible copolymer which is a copolymer based on lactic and glycolic acid having a monomer ratio of lactic to glycolic acid in the range from 50:50 to 75:25, and at least one water-miscible solvent with a dipole moment about 3.9-4.3 D, wherein the viscosity of the solution comprising the polymer and the solvent is between 0.5 and 3.0 Pa∙s and the solvent/drug mass ratio is between 10 and 4, and wherein the drug/polymer mass ratio is between 25 and 35% expressed as the weight percentage of the drug with respect of the drug plus polymer, the particle size distribution of the drug is as follows: less than 10% particles smaller than 10 microns, less than 10% particles larger than 225 microns, and a d0.5 value in the range of 60-130 microns. Once the composition contacts the body fluids, the polymer matrix hardens retaining the drug, forming a solid or semisolid implant that releases the drug in a continuous manner. Therapeutic plasma levels of the drug can be achieved since the first day up to at least 14 days or more.Изобретение представляет собой композиции для инъекционных, образующихся in-situ биоразлагаемых имплантатов пролонгированного действия, служащих для доставки в организм антипсихотического лекарственного средства рисперидона и обеспечения его терапевтической концентрации в плазме крови с первого дня. Композиция представляет собой инъекционную композицию пролонгированного действия (депо), включающую лекарственное средство рисперидон и/или 9-ОН-рисперидон по меньшей мере один биосовместимый полимер, представляющий собой сополимер на основе молочной и гликолевой кислоты,
