Cefacetrile (INN, also spelled cephacetrile) is a broad-spectrum first generation cephalosporin antibiotic effective in gram-positive and gram-negative bacterial infections. It is a bacteriostatic antibiotic. Cefacetrile is marketed under the trade names Celospor, Celtol, and Cristacef, and as Vetimast for the treatment of mammary infections in lactating cows.