The invention relates to biomedicine and nanomedicine, and makes it possible to enhance the diagnostic or therapeutic efficiency of an agent administered to the organism. The invention can be used to enhance methods of diagnostics and therapy of various diseases due to a more effective (passive or active) delivery of the agent to cell-targets, improved pharmacokinetic parameters of the agent (circulation time), etc. The essence of the invention consists in a substance for enhancing the diagnostic or therapeutic efficiency of an agent administered to the organism, this substance comprising a component that, upon administration of the substance to the organism, enables elimination from the bloodstream by the reticuloendothelial system of at least the objects, which circulate in the bloodstream but do not represent artificially created nanoparticles or microparticles, or opsonins that non-specifically bind to said component, and said elimination of said objects causes blockade, at least partial, of the reticuloendothelial system. The technical result of application of the invention consists in creation of the method for blockade of the cells of reticuloendothelial system by means of administration of a small amount of a foreign substance or a safe biocompatible substance, and also the result consists in enhancement (boosting) of the blockade effect.
