Radiosensitivity study of cefazolin sodium

The extent of physico-chemical changes induced by irradiation of cefazolin sodium was investigated. The methods used were potency determination, impurity profile, colour measurements and pH measurements. The potency of irradiated samples at 25 kGy was 4+/-2% lower than that of the non irradiated ones. The total amount of related substances increased from 0.72+/-0.01% in the non irradiated samples to 4.9+/-0.7% in the samples irradiated at 25 kGy. Most of the peaks showed trace amounts (<0.01%), the largest one represented 1.2+/-0.5% of the total related substances. Only two peaks were identified by chromatography: the methyl-1,2,3-thiazol-2 thiol-5 and the 7-aminocephalosporanic acid. The latter related substance is only produced by the irradiation of cefazolin sodium. The pH values of the samples were within the specifications of the European Pharmacopoeia. The colour of the cefazolin sodium powder changed from white to yellow upon irradiation. The yellow colour persisted after the dissolution of the powder. Most of the tests carried out met the Pharmacopoeia's specifications, except the one concerning the colour of the solution.