Evaluation of stability of oxytetracycline-HCl to sterilization levels of gamma radiation.

The effect of gamma irradiation at different dose levels (from 5 to 50 KGy) on the solid state of the antibiotic oxytetracycline-HCl was examined. The results obtained showed no effect on the biological activity of the compound, as investigated by the bioassay technique. The physicochemical properties of the antibiotic were not altered by irradiation dose levels up to 40 KGy. The UV-visible spectra of all irradiated samples showed no changes. The I.R. spectra of oxytetracycline, exposed to dose levels higher than 40 KGy, showed, however, definite destruction in the chemical structure of the antibiotic. HPLC separation of samples, irradiated at 45 KGy, showed the presence of new degradation products. Accordingly, sterilization of oxytetracycline by use of gamma irradiation could be considered safe and applicable, since sterilization doses are usually considered to be less than 30 KGy.