Cloxacillin

What it is and how it works

Cloxacillin is a bactericidal beta-lactam that inhibits bacterial cell-wall synthesis by binding penicillin-binding proteins. Its side chain makes it resistant to staphylococcal penicillinase, so it is active against penicillinase-producing, methicillin-susceptible Staphylococcus aureus.

Indications

Infections caused by penicillinase-producing staphylococci, including skin and soft-tissue infections, osteomyelitis, septic arthritis, pneumonia, endocarditis and septicaemia (methicillin-resistant strains are resistant).

Dosage and administration (summary)

Oral (adults): 500 mg every 6 hours, taken at least 30–60 minutes before food. Parenteral: 250–500 mg every 4–6 hours by intramuscular or intravenous injection, increased up to 1–2 g every 4–6 hours by intravenous infusion in severe infections.

Contraindications

Hypersensitivity to penicillins; history of cloxacillin- or flucloxacillin-associated jaundice or hepatic dysfunction.

Warnings and precautions

Serious hypersensitivity reactions including anaphylaxis may occur; cross-sensitivity with cephalosporins is possible. Cholestatic jaundice and hepatitis may occur, sometimes delayed, particularly in the elderly and with prolonged treatment; monitor liver function on long courses. Clostridioides difficile-associated diarrhoea may develop; high doses require caution in renal impairment (sodium load and neurotoxicity).

Pregnancy

Penicillins are generally considered safe in pregnancy.

Storage and supply

Store below 25 °C, protected from moisture; use reconstituted injection promptly.

Source: reference summary prepared from the EU SmPC/EPAR, BNF and WHO Model Formulary. The approved product information in Iran governs.