Protective effect of scavengers and surfactants on gamma irradiated cortisone acetate aqueous solutions

Abstract

Gamma radiation offers several advantages over other methods as a sterilization technique including high efficiency, used at room temperature, appreciable penetration to sealed containers and being a terminal and continuous operation. The purpose of the research is to investigate the protective effect of different types of free radical scavengers or surfactants on cortisone acetate degradation in aqueous solution during sterilization by gamma radiation. Cortisone acetate aqueous solution was subjected to increasing doses of gamma radiation up to the sterilizing dose (25 kGy). The effect of the main radiolytic products of water, hydroxyl radicals (OH·), hydrogen atoms (H·), and hydrated electrons (e eq ) was studied separately to identify the most destructive species. The results showed a high sensitivity of the drug to radiation even at doses much lower than sterilization. The destructive effects of the radiolytic products of water could be arranged in the following order; OH·> H·> e eq . The effect of free radical scavengers, namely methanol and 2-propanol on drug stability to radiation was also investigated. The results revealed a higher protective effect for 2-propanol than methanol. Anionic, cationic or non-ionic surfactants were used in different concentrations below and above their critical micelle concentrations (CMC) to stabilize the drug during irradiation. The presence of cetyl trimethyl ammonium bromide (CTAB), sodium lauryl sulfate (NaLS) or cetomacrogol 1000 as representative examples for cationic, anionic and non-ionic surfactants, showed a protective effect for the drug against radiation. The protective effect was found to be proportional to the surfactant concentration to a certain limit, above which further increase in surfactant concentration had no effect. The maximum protective effect of the ionic surfactants was found to be at their CMC due to the association of the drug with the formed micelles. The stabilizing effect of different surfactants could be arranged in the following order; NaLS > CTAB > cetomacrogol 1000.