nafcilina

Nafcillin is a beta-lactam antibiotic in the penicillin class, specifically an isoxazolyl penicillin. It is designed to resist penicillinase produced by Staphylococcus aureus and works by inhibiting bacterial cell wall synthesis through binding to penicillin-binding proteins, leading to bacterial lysis. Its spectrum is focused on penicillinase-producing Staphylococcus aureus (primarily methicillin-susceptible S. aureus, MSSA) and certain streptococci; it is not active against methicillin-resistant S. aureus (MRSA) and has limited activity against many Gram-negative organisms.

Nafcillin is used for serious MSSA infections, including bacteremia, endocarditis, osteomyelitis, septic arthritis, and complicated skin and soft tissue infections when MSSA is suspected. It is chosen for infections caused by penicillinase-producing Staphylococcus aureus but should not be used for infections due to MRSA or organisms without beta-lactamase resistance.

Administration and pharmacokinetics are characterized by parenteral use; oral administration is ineffective due to poor bioavailability. Nafcillin is cleared mainly by hepatic metabolism with biliary excretion, so hepatic function can influence drug levels; renal impairment typically does not require dose adjustment, though individual hepatic compromise may necessitate changes. Dosing is given intravenously in appropriate hospital settings, with duration guided by infection severity and response.

Adverse effects and safety considerations include hypersensitivity reactions, rash, and fever. Prolonged use may be associated with cholestatic jaundice and neutropenia; superinfection can occur. It is contraindicated in individuals with penicillin allergy.

Nafcillin is one of the antistaphylococcal penicillins used for MSSA infections, alongside agents such as oxacillin and dicloxacillin, and is not effective against MRSA or many Gram-negative pathogens.