Dicloxacillin

Dicloxacillin is a penicillinase-resistant beta-lactam antibiotic of the isoxazolyl penicillin group. It is used to treat infections caused by penicillinase-producing Staphylococcus aureus and by certain streptococci. It is less active against Gram-negative organisms and is not effective against methicillin-resistant Staphylococcus aureus (MRSA).

Mechanism of action and spectrum: Dicloxacillin inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins, leading to cell lysis. It is primarily active against penicillinase-producing Staphylococcus aureus and certain streptococci, but has limited activity against Gram-negative bacteria and does not cover MRSA or most enterococci.

Pharmacokinetics and administration: Following oral administration, dicloxacillin is fairly acid-stable and is absorbed with appreciable bioavailability. It is primarily excreted by the kidneys, with a short half-life that necessitates dosing every six hours in adults.

Clinical use and dosing: It is used for uncomplicated skin and soft tissue infections, wound infections, and other infections caused by susceptible organisms. The usual adult oral dose is 125–500 mg every six hours, with adjustment for infection severity and patient factors; therapy typically lasts 5–10 days.

Adverse effects and interactions: Common adverse effects include gastrointestinal upset, diarrhea, and rash; hypersensitivity reactions can occur. Cross-reactivity with other penicillins is possible. Rare adverse events include cholestatic jaundice and superinfections, such as C. difficile. Probenecid can increase dicloxacillin levels; allopurinol may raise rash risk; concurrent use with certain anticoagulants may alter effects.

Resistance and limitations: Resistance arises mainly through beta-lactamase production and altered penicillin-binding proteins. Dicloxacillin is not active against MRSA or many resistant Gram-negative pathogens.