Cephalothin and cefazolin

Cephalothin (also spelled cefalothin and cefalotin) and cefazolin (also spelled cephazolin) are semisynthetic cephalosporins derived from cephalosporin C, a natural antibiotic produced by a strain of the fungus Acremonium chrysogenum (previously known as Cephalosporium acremonium) (Griffith and Black, 1964). The cephalosporin C nucleus, 7-ACA, is closely related but not identical to the penicillin nucleus, 6-APA. Although very similar compounds (Wick and Preston, 1972), cefazolin was introduced after cephalothin with the practical advantage of maintaining higher serum concentrations because of its longer half-life. Both cephalothin and cefazolin are described as first-generation cephalosporins.