Among many sterilization methods, radiosterilization is a preferred method in the pharmaceutical industry because of its advantages. However, the detection of radiosterilization of drugs is a growing concern for many government regulatory agencies around the world because of changes in the drug's structure because of exposure to radiation. Electron Paramagnetic Resonance (EPR) proved to be a very sensitive technique to discriminate between irradiated and nonirradiated drugs and detect radicals for days even to years. In this study, the focus is on the detection of radiosterilization of irradiated three asthma drugs (Airfix, Ventolin and Prednol) by using EPR spectroscopy. Regarding the commercial aspects of drugs, it was found that radicals can be detected at least 2 y after irradiation. Therefore, paramagnetic centers formed by the effect of radiation in the samples were determined and the stability of these centers was examined for 2 y by performing the fading study.