In Vitro: Oxacillin inhibits gram positive pathogens with MICs of 0.05, 0.09, 0.32 and 0.80 μg/mL against group A streptococci, Pneutnococci, susceptible staphylococci and penicillin-resistant staphylococci, respectively. The Oxacillin-resistant strains are highly resistant to other penicillins.
In Vivo: Oxacillin (50-800 mg/kg; s.c.; once) shows curative dose (CD50) of 253.3 mg/kg in mice infected with Staphylococcus aureus Evans. The oral CD50 of Oxacillin is 187.2 mg/kg.