Cefmetazole free acid is a second generation cephalosporin antibiotic that has a broad range of activity against gram-negative and gram-positive bacterium. Cefmetazole has exhibited great bactericidal activity against Staphylococcus aureus, which includes some methicillin-resistant strains.

Cephalosporins are a type of β-lactam antibiotic consisting of a four-membered β-lactam ring bound to a six-membered dihydrothiazine ring. This two-ring system causes distortion of the β-lactam amide bond, resulting in decreased resonance stabilization and increased reactivity. β-lactams inhibit the formation of peptidoglycan cross-links within bacterial cell walls by targeting penicillin-binding proteins or PBPs. Consequently, the bacterial cell wall becomes weak and cytolysis occurs. Cephalosporins are less susceptible to β-lactamases than the penicillin β-lactam antibiotics.

Antibiotics are often used in clinical in vitro tests known as antimicrobial susceptibility tests or ASTs to determine their efficacy against certain bacterial species. They are tested against gram-negative and gram-positive bacteria using panels, discs, and MIC strips by medical microbiologists. ASTs decrease the risk of using an antibiotic against bacteria exhibiting resistance to it, and the results are used in clinical settings to determine which antibiotic(s) to prescribe for various infections.