(2S,5R,6R)-3,3-Dimethyl-6-[[(5-methyl-3-phenyl-4-isoxazolyl)carbonyl]amino]-7-oxo-4-thia-1-azabicyclo[3.2.0]heptane-2-carboxylic Acid Sodium Salt; Penicillin P-12; Sodium Oxacillin; BRL-1400; Bactocill; Bristopen; Stapenor; Micropenin; NSC 527712; SQ16423

Oxacillin is a penicillinase-resistant β-lactam. It is similar to methicillin, and has replaced methicillin in clinical use. Another related compound is nafcillin. Since it is resistant to penicillinase enzymes, such as that produced by Staphylococcus aureus, it is widely used clinically in the US to treat penicillin-resistant Staphylococcus aureus. However, with the introduction and widespread use of both oxacillin and methicillin, antibiotic-resistant strains called oxacillin-resistant Staphylococcus aureus (MRSA/ORSA) have become increasingly prevalent worldwide. MRSA/ORSA is treated using vancomycin.