oksasilliini

Oksasilliini, or oxacillin, is a beta-lactam antibiotic in the penicillinase-resistant group (isoxazolyl penicillins). It is used to treat infections caused by penicillinase-producing staphylococci, particularly methicillin-susceptible Staphylococcus aureus, and some streptococcal infections. It is ineffective against methicillin-resistant Staphylococcus aureus (MRSA) and has limited activity against many Gram-negative bacteria and anaerobes.

The mechanism of action is similar to other beta-lactams: it inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins, leading to disruption of cell wall formation and bacterial cell death. Oxacillin is usually administered by injection because it has poor oral bioavailability.

Administration and dosing are primarily parenteral, given intravenously or intramuscularly. Dosing regimens vary with infection severity and patient characteristics and are typically divided into multiple daily doses; adjustments may be needed for renal or hepatic impairment. The drug is supplied as sodium or potassium salts. Oral formulations are uncommon and not routinely used.

Pharmacokinetics and safety considerations include hepatic handling and biliary excretion, which can be associated with cholestatic liver injury or jaundice, especially with prolonged high-dose therapy. Serum levels can be influenced by liver function and drug interactions such as with probenecid. Common adverse effects are hypersensitivity reactions, rash, and gastrointestinal upset; less frequent but notable risks include liver enzyme abnormalities and hematologic effects.

Resistance remains primarily due to beta-lactamase production by bacteria. Oxacillin provides activity against penicillinase-producing staphylococci but does not cover MRSA, many Gram-negative bacteria, or anaerobes, and its use should be guided by susceptibility data.