ESR identification of radiosterilized pharmaceuticals: latamoxef and ceftriaxone

As an alternative to heat and gas exposure sterilization, ionizing radiation is gaining interest as a sterilization process for medicinal products. The aim of this work was to develop equations to describe the ESR curves versus dose and storage time after gamma irradiation of latamoxef and ceftriaxone. Limit of detection and limit of discrimination are (0.5 kGy, 1.5 kGy) and (1.5 kGy, 5 kGy) for latamoxef and ceftriaxone respectively. Linear regression is, for latamoxef, applicable for doses lower than 20 kGy. Since the radiation dose selected must always be based upon the bioburden of the products and the degree of sterility required (ANSI/AAMI/ISO 11137), doses in the range 5-20 kGy could be investigated and linear regression would appear to be the least expensive route to follow. Bi-exponential function is of more general applicability to predict irradiation dose in latamoxef. The comportment of ceftriaxone is different. Due to the weak number of free radicals generated during the irradiation, only two models give correct adequacy between experimental and calculated results. Decay kinetics for radicals versus storage were considered. The free radicals decay could be simulated by exponential and bi-exponential functions for latamoxef and ceftriaxone respectively. The limits of detection of free radicals after irradiation at 25 kGy are 140 days for latamoxef and 115 days for ceftriaxone. (C) 1997 Elsevier Science B.V.