The present invention concerns a product enabling a solid implant to be formed, by injection, inside the body of a subject, said product comprising a pharmaceutically acceptable base composition that contains at least a solvent and at least a first polysaccharide soluble in said solvent, said base composition being capable of forming a precipitate upon contact with an optionally saline aqueous solution. The product characteristically further comprises a given quantity of at least one pharmaceutically acceptable active substance, chosen from: - ionic bactericidal/antiseptic/antifungal agents that are soluble or miscible in said solvent such as eosin and methylene blue and potassium iodide； - antibiotics, growth factors, hydroxylapatite, hormones, anti-tumour agents, antimitotic agents, topoisomerase inhibitors, anti-cancer agents and mixtures of at least two of said active substances, in particular in power form； and - radionuclides； said quantity of active substance is mixed with said base composition or packaged separately from said base composition, and the mixture formed by said base composition and said quantity of active substance has a viscosity that allows said mixture to be injected, and said mixture forms a precipitate upon contact with an optionally saline aqueous solution.La présente invention concerne un produit permettant par injection la formation d'un implant solide dans le corps d'un sujet, ledit produit comprenant une composition de base, pharmaceuticalement acceptable, qui contient au moins un solvant et au moins un premier polysaccharide soluble dans ledit solvant, ladite composition de base est apte à former un précipité au contact d'une solution aqueuse éventuellement saline. De manière caractéristique, le produit comprend, en outre, une quantité donnée d'au moins une substance active, pharmaceuticalement acceptable, choisie parmi : - les agents bactéricides/antiseptiques/antifongiques ioniques et solubles ou miscibles dans ledit solvant tels qu
