Cefazolin-13C2,15N is intended for use as an internal standard for the quantification of cefazolin by GC- or LC-MS. Cefazolin is a broad-spectrum cephalosporin antibiotic that is active in vitro against various Gram-positive and Gram-negative bacteria (MICs = 0.2-12.5 μg/ml). It also inhibits the growth of clinical isolates of S. aureus, E. coli, P. mirabilis, and K. pneumoniae (MICs = 0.1-25 μg/ml). In vivo, cefazolin protects against S. aureus, E. coli, and P. mirabilis infection in mice (ED50s = <0.09-1.78, 0.44-3.63, and 2.31-5.2 mg/animal, respectively). Formulations containing cefazolin have been used to treat a variety of bacterial infections.
5-Fluorouracil-13C,15N2 is intended for use as an internal standard for the quantification of 5-flurouracil by GC- or LC-MS. 5-Fluorouracil is a pyrimidine analog that irreversibly inhibits thymidylate synthase, blocking the synthesis of thymidine which is required for DNA synthesis. Intracellular metabolites of 5-fluorouracil exert cytotoxic effects by either inhibiting thymidylate synthetase, or through incorporation into RNA and DNA, ultimately initiating apoptosis.