Antibiotic — Penicillinase-Resistant Penicillin Pregnancy: Limited information in human pregnancy (no teratogenic effects in animal studies) — use only when the potential benefits outweigh the potential risks; trace quantities are detectable in breast milk and hypersensitivity reactions in the breastfed infant must be considered, so use in breast-feeding only when benefits outweigh risks

Flucloxacillin (Burns — Wound Infection)

Brand names: Floxapen

Flucloxacillin is a penicillinase-resistant (isoxazolyl) penicillin used here for established or suspected wound infection in burns, where Staphylococcus aureus and beta-haemolytic streptococci predominate.

Auto-extracted from the source labelling — not yet independently clinician-verified. These values were distilled from the UK SPC (or the US label where noted) but have not had a clinician sign-off. Confirm against the current SmPC before prescribing.

Adult dose

Dose: 250 mg to 1 g every six hours by slow intravenous injection or by infusion; these doses may be doubled in severe infections

Route: Slow intravenous injection over three to four minutes, or by infusion (may also be added to infusion fluids or injected suitably diluted into the drip tube over three to four minutes); intramuscular, intra-articular, intrapleural and nebulised routes are also licensed

Frequency: Every 6 hours

Max: No single bolus injection or infusion should exceed 2 g; the maximum dose of 12 g per day should not be exceeded

Source is the SPC for Flucloxacillin 1000 mg powder for solution for injection or infusion; the regimen above is the usual adult dose, including the elderly. The SPC gives NO burns-specific or wound-infection-specific regimen — dose depends on age, weight and renal function of the patient as well as the severity and nature of the infection. Other stated regimens: osteomyelitis — doses of up to 8 g daily in 3 to 4 divided doses have been suggested; endocarditis — 8 g daily in four divided doses in patients weighing up to 85 kg, and 12 g daily in 6 divided doses in those weighing more; surgical prophylaxis — 1 to 2 g intravenously at induction of anaesthesia followed by 500 mg six hourly intravenously or intramuscularly for up to 48 hours; intramuscular injection — 250 mg four times daily; intrapleural injection — 250 mg once daily; nebuliser — 125 to 250 mg four times daily; intra-articular injection — 250 to 500 mg once daily. No dose reduction is necessary in reduced hepatic function. During prolonged treatment (e.g. osteomyelitis, endocarditis) regular monitoring of hepatic and renal function is recommended. The injection contains approximately 51 mg sodium per g. NOTE: the eMC fetch was truncated part-way through §4.4, so §4.5 interactions were not retrieved — check the full SPC.

Paediatric dose

Route: Intramuscular or intravenous injection

Frequency: Three to four equally divided doses per 24 hours

Max: No single bolus injection or infusion should exceed 33 mg/kg

SPC §4.2, children under 14 years of age: 25 to 50 mg/kg/24 hours administered in three to four equally divided doses by i.m. or i.v. injection. dosePerKg is left null because the SPC states a range rather than a single value. The SPC adds that children aged 10 to 14 years usually receive a daily dose of 1.5 g to 2 g and children aged 6 to 10 years 0.75 g to 1.5 g, divided into three to four equal doses, and that in cases of severe infections up to 100 mg/kg/24 hours in three to four divided doses may be used. Verify all paediatric dosing against a children's formulary before use.

Dose adjustments

Renal

Dosage reduction is not usually required; however in severe renal failure (creatinine clearance <10 ml/min) a reduction in dose or an extension of the dose interval should be considered, with a maximum recommended dose of 1 g every 8 to 12 hours. Flucloxacillin is not significantly removed by dialysis, so no supplementary doses are needed during or at the end of dialysis. Care is necessary with very high doses if renal function is poor, because of the risk of nephrotoxicity

Dose auto-extracted from UK Summary of Product Characteristics (SPC) via the eMC — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

Contraindications

History of hypersensitivity to beta-lactam antibiotics (e.g. penicillins, cephalosporins)
Previous history of flucloxacillin-associated jaundice or hepatic dysfunction
Ocular or subconjunctival administration

Side effects

Common: minor gastrointestinal disturbances
Uncommon: rash, urticaria and purpura
Very rare: hepatitis and cholestatic jaundice (may be delayed up to two months post-treatment, may be protracted and severe, with deaths reported — mostly in patients over 50 years and those with serious underlying disease)
Very rare: anaphylactic shock and angioneurotic oedema
Very rare: neutropenia (including agranulocytosis), thrombocytopenia, eosinophilia and haemolytic anaemia
Very rare: pseudomembranous colitis; erythema multiforme, Stevens-Johnson syndrome and toxic epidermal necrolysis; acute generalised exanthematous pustulosis (frequency not known); hypokalaemia; convulsions with high intravenous doses in renal failure

Interactions

Paracetamol — caution when co-administered because of the increased risk of high anion gap metabolic acidosis (HAGMA), particularly in severe renal impairment, sepsis or malnutrition and especially at maximum daily paracetamol doses; close monitoring is recommended (from §4.4)
eMC §4.5 was not retrieved by the source fetch (truncated during §4.4) — the full interactions section must be checked against the SPC

Clinical monograph

How it works

It inhibits bacterial cell-wall synthesis by binding penicillin-binding proteins, and its acyl side chain resists staphylococcal beta-lactamase, retaining activity against most meticillin-sensitive S. aureus.

Prescribing in practice

Cholestatic hepatitis and jaundice can occur, sometimes weeks after stopping, and risk rises with prolonged courses and increasing age — counsel and avoid unnecessarily long treatment.
It has no useful activity against MRSA or Gram-negative organisms, so review wound cultures and broaden or switch if these are isolated.
Avoid in patients with a history of penicillin hypersensitivity and take care to distinguish true allergy from non-immune reactions before labelling.

Monitoring

Monitor clinical response and the wound, and check liver function during prolonged or high-intensity courses given the risk of cholestatic injury.

Counselling the patient

Take on an empty stomach, well before food, as absorption is reduced by food.
Report yellowing of the skin or eyes, dark urine or pale stools, even after the course has finished.

Evidence & guidelines

Flucloxacillin is the standard first-line agent for staphylococcal soft-tissue infection in UK practice, with MHRA advice highlighting the risk of cholestatic hepatic reactions.

Reference: MHRA Drug Safety Update (Flucloxacillin Hepatotoxicity); BBA Burns Infection Guidelines; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Curated clinical cross-links plus same-class fallbacks.

Calculators