Cefapirin (INN, also spelled cephapirin) is an injectable, first-generation cephalosporin antibiotic. It is marketed under the trade name Cefadyl. Production for use in humans has been discontinued in the United States. Cefapirin (INN, also spelled cephapirin) is an injectable, first-generation cephalosporin antibiotic. It is marketed under the trade name Cefadyl. Production for use in humans has been discontinued in the United States. It also has a role in veterinary medicine as Metricure, an intrauterine preparation, and combined with prednisolone in Mastiplan, an intramammary preparation. Both are licensed in cattle. In one of the syntheses, 7-aminocephalosporanic acid (7-ACA) is reacted with bromoacetyl chloride to give the amide. The halo group is then displaced by 4-thiopyridine.