Oxacillin is an orally active synthetic penicillin that exhibits effective bactericidal activity against staphylococci and other gram-positive pathogens.

Oxacillin effectively inhibits Gram-positive pathogens, exhibiting minimum inhibitory concentrations (MICs) of 0.05, 0.09, 0.32, and 0.80 μg/mL against Group A streptococci, Pneumococci, susceptible staphylococci, and penicillin-resistant staphylococci, respectively [1]. Additionally, strains resistant to Oxacillin show a high level of resistance to other penicillins [1].

Oxacillin, administered subcutaneously at dosages ranging from 50 to 800 mg/kg (single dose), demonstrated a curative dose (CD 50) of 253.3 mg/kg for CD-1 strain male albino mice infected with Staphylococcus aureus Evans. In contrast, the oral CD 50 for Oxacillin was found to be 187.2 mg/kg. This therapeutic activity highlights Oxacillin's effectiveness against S. aureus Evans infections in mice [2].