Oxacillin is a broad-spectrum penicillin-based antibiotic used in the treatment of bacterial infections in the human body. It is mainly used to fight off Penicillinase-resistant staphylococcal bacteria. Oxacillin's resistance to Penicillinase enzymes makes it the best choice in fighting penicillin-resistant Staphylococcus aureus. Its widespread use has led to strains resistant to Oxacillin and sister drug Methicillin. The strains are treated using Vancomycin.