FIELD : pharmacology; veterinary medicine.SUBSTANCE : invention relates to the field of pharmacology and veterinary medicine and describes interpolymer polyelectrolyte complexes of a cationic polymer – polyalkylcarboxylic (polyacrylic or polymethacrylic) acid with anionic copolymer – N-vinylpyrrolidone and 2-methyl-5-vinylpyridine or 4-vinylpyridine or 2-vinylpyridine. Interpolymer polyelectrolyte complexes are biodegradable and are capable of destruction as a result of gradual destruction by the action of electrolytes and enzymatic systems present in the body of humans and animals.EFFECT : prolonged medicinal and veterinary agents based on the above interpolymer polyelectrolyte complexes can be used as carriers of chemotherapeutic agents or basis for implants formed in situ.6 cl, 1 dwg, 4 ex, 4 tbl