[The classification of radiation protective agents as the reflection of the present state and development perspective, of current radiation pharmacology].

Pharmacological drugs which can reduce the radiation damage to the organism when applied in the nearest time before or after exposure to radiation can be referred to as radiation protective agents. The classification of radiation protective agents, which has been well established to date, is a reflection of the history of the formation and current state of radiation pharmacology: the most significant historical landmarks in the screening of radiation protective agents among different groups of pharmaceutical preparations and the formation of the theoretical knowledge about the mechanism for their radiation protective effects. It consists of: (1) radioprotectors which realize their radiation protective effect at the physical, chemical and biochemical levels in the course of the energy absorption of ionizing radiation via partial neutralization of the "oxygen effect" as a radiobiological phenomenon; (2) radiomitigators, which realize their effect at the system level by accelerating the post-radiation recovery of radiosensitive tissues through an activation of proinflammatory signaling pathways and an increase of secretion of hematopoietic growth factors, are used in the early period after exposure to radiation prior to the development of clinical manifestations of acute radiation damage as drugs of emergency and early treatment for radiation injuries; (3) radiomodulators--pharmaceutical drugs and food nutritional supplements which elevate the resistance of the organism to adverse environmental factors, including mutagenic effects of exposure to low-dose ionizing radiation, by means of modulating the gene expression through "substrate" maintenance of adaptive changes resulting in an increased antioxidant protection of the organism; (4) pharmaceutical drugs to protect against the incorporation of technogenic radionu- clides into the organism; (5) pharmaceutical drugs to prevent (arrest) manifestations of the primary response to radiation.