Summary:
Gamma irradiation is an excellent technique for the sterilization of pharmaceutical raw materials and products (1,2) . One of the major possible disadvantages of radiosterilization is the production of new radiolytic intermediates during the irradiation process (3) .
The Radiosterilization was carried out for sulfathiazole (antibacterial product) powder and model ophthalmic solution in this research. Irradiation at room temperature at radiation doses of 10, 25 and 40 kGy was investigated via different physical, chemical, microbiological and biological techniques both in normal and accelerated stability conditions (40±2°C and 75±5 % relative humidity, 3 months).
Changes in organoleptic features, pH, melting point, UV, IR, NMR, TLC, ESR, DSC characteristics, and microbiological activities of active compound at normal and accelerated stability test conditions were studied.
It was observed that UV, IR, and NMR characteristics of sulfathiazole did not change with the applied dose ranging between 10-40 kGy except ?max values of irradiated solid samples dissolved in 0.1 N HCl solution. Some radicals were detected by ESR signal intensity of solid samples. Attempt for determination of radicals produced in irradiated model ophthalmic solution by ESR technique failed due to the short life of these radicals in solution.
The results obtained under accelerated stability test conditions over a period of three months were observed to be consistent with the reference values and the activity of sulfathiazole remained unaffected even at the end of the test period. Microbiological and biological properties both in normal and accelerated conditions were also investigated. Based on the physical, chemical, microbological and biological results, the optimum radiation dose of 10 kGy can be applied for the sterilization of sulfathiazole powder and model ophthalmic solution.

Keywords:
Sulfathiazole, Irradiation of drugs, Radiosterilization, Gamma irradiation, Stability.