Sensitivity of hydrocortisone to gamma radiation in topical preparations

The sensitivity of hydrocortisone to gamma radiation in aqueous and organic solvents was investigated to predict the feasibility of sterilizing the topical preparations by radiation. The drug showed a higher sensitivity to radiation in aqueous solutions than organic ones. Adding different types of surfactants like NaLS, CTAB or Cetomacrogol 1000 to aqueous solutions before irradiation resulted in a considerable protective effect, following the order NaLS > CTAB > Cetomacrogol1000. From the calculated G-values, it was evident that the sensitivity of organic solutions of the drug to radiation increased as the number of hydroxyl groups in the aliphatic alcohol increased. Also the position of hydroxyl groups in the aliphatic chain affected drug degradation rate. The sensitivity of drug to radiation in organic solvents was in the order: 1,3 propanediol > glycerol > propylene glycol > n-propanol. The high stability of the formulated creams to radiation was suggested to be due to the protective effect of the long-chain stearyl alcohol in the organic phase as well as the effect of NaLS in the aqueous phase. On the other hand, the stability of the drug in the formulated ointments was considerably affected by the propylene glycol content and slightly protected by cetyl alcohol.