ESR spectroscopy applied to the study of drugs radiosterilization: Case of three nitroimidazoles

The use of ionizing radiation for sterilization of pharmaceuticals is now a well esablished technology. In this paper, we examined the time stability at ambient conditions and higher temperatures of free radicals produced after the gamma irradiation of three nitroimidazoles: metronidazole, ornidazole and ternidazole The bi-exponential model used to fit the decay curves showed, in major cases, two simultaneous phases: the first corresponding to a fast ‘pure’ exponential decay; and, a second corresponding to a slowly ‘quasi linear’ decay, possibly due to a solid diffusion mechanism.