Flucloxacillin

Flucloxacillin is better absorbed from the gut than cloxacillin.

Indications are infections due to penicillinase producing Staphylococci.

Cautions include:

• history of allergy
• renal impairment

Contra-indications include:

• porphyria
• related to liver disease (1)
  • flucloxacillin should not be used in patients with a history of flucloxacillin-associated jaundice or hepatic dysfunction.
  • flucloxacillin should be used with caution in patients with evidence of hepatic dysfunction
  • careful enquiry should be made concerning previous hypersensitivity reactions to ß-lactams.

Side-effects: (2)

• see 'penicillins (general side-effects)'

Common or very common

Gastrointestinal disorders

Rare

Eosinophilia

Frequency not known

Hypokalaemia; oesophageal disorder; oral pain; oropharyngeal pain; throat irritation

With parenteral use

Bronchospasm; coma; dyspnoea; electrolyte imbalance; erythema nodosum; hallucination; Jarisch-Herxheimer reaction; nephropathy; neurotoxicity; oral candidiasis; platelet dysfunction; purpura non-thrombocytopenic; vasculitis

Potentially life-threatening hypokalaemia can occur, especially in high doses. This can be resistant to potassium supplementation. Regular monitoring of serum potassium levels is recommended when using higher doses of flucloxacillin.

Routes of administration:

• oral
  • capsules
  • syrups
• intramuscular
• slow intravenous injection
• intravenous infusion

The summary of product characteristics must be consulted before prescribing this drug.

Reference:

1. Petersen I, Hayward AC, on behalf of the SACAR Surveillance Subgroup. Antibacterial prescribing in primary care. J Antimicrob Chemother 2007; 60 Suppl 1: i43–7
2. NICE: BNF: Drugs: Flucloxacillin (online 2026)