Trends in the development of radioprotective agents.

People may be exposed to ionizing radiation during radiotherapy or following exposure to radionuclides in nuclear medicine. Radioprotective agents have been used to reduce morbidity or mortality produced by ionizing irradiation. Early developments of such agents focused on thiol synthetic compounds, such as amifostine. This compound reduced mortality; however, there were difficulties in administering aminothiols that led to adverse effects. Hence, the development of radioprotective agents with lower toxicity and an extended window of protection has attracted much attention. Natural compounds have been evaluated as radioprotectants and they seem to exert their effect through antioxidant and immunostimulant activities. Although recent agents have lower efficacy, they have lower toxicity, more favourable administration routes and improved pharmacokinetics compared to the older thiol compounds.