Photo-stability of Cefotaxime in Aqueous Vitamin Solutions

We investigated the photo-stability of some third-generation cephalosporins in aqueous solution containing such vitamins, as vitamin B1, B2, B6, C, K2, and panthenol. Although cephem derivatives are stable in aqueous solution without vitamins during 4 hours of sun light irradiation at room temperature, sun light irradiation for 2 hrs did cause the photodegradation of cefotaxime (CTX) in aqueous solution (2 mg/ml) containing flavin adenine dinucleotide (FAD, VB2 derivative) or pyridoxal phosphate (PAL-P, VB6 derivative), while, in addition, the residual rate of CTX in the solution also decreased to less than 70%. Similarly, the residual rate of CTX in a solution of benzophenon, a triplet photosensitizer, also rapidly decreased during sun light irradiation. Sun light irradiation also decreased the residual rates of other cephalosporins with an oxyimino group at position 7 under the same conditions. The main degradation product was identified as an anti-isomer of CTX. These above described findings thus suggest that FAD and PAL-P may act as photosensitizers in the sun light-induced degradation of cephalosporins.