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Antibiotic — Penicillinase-Resistant

Flucloxacillin

Brand names: Floxapen

Used in: Cellulitis & Skin Infection

Flucloxacillin is a penicillinase-resistant penicillin used for staphylococcal and streptococcal infections, including skin and soft-tissue infections.

Dosing — being independently re-sourced

ClinCalc Pro is rebuilding its dose data from primary open sources — the manufacturer SmPC (eMC), the WHO Model Formulary and other official references — under clinician review. This drug's structured dose is not yet published here. Confirm all doses against the product SmPC and your local formulary before prescribing.

Clinical monograph

How it works

A beta-lactam, stable to staphylococcal penicillinase, that inhibits bacterial cell-wall synthesis.

Prescribing in practice

  • Contraindicated in penicillin allergy and in previous flucloxacillin-associated jaundice or hepatic dysfunction.
  • Cholestatic hepatitis can occur, sometimes up to several weeks after stopping, and is more common in older patients and with prolonged courses.
  • Take it on an empty stomach for better absorption.

Monitoring

Consider liver function with prolonged courses; review clinical response.

Counselling the patient

  • Take it before food and complete the course.
  • Report yellowing of the skin or eyes or dark urine, even after finishing the course.

Evidence & guidelines

First-line for staphylococcal skin and soft-tissue infection (e.g. cellulitis) per NICE/PHE guidance.

Reference: RCOphth Orbital Cellulitis Guidelines; MHRA Drug Safety Update (cholestatic jaundice); Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. Monograph status: clinician-reviewed (2026-07-04).

Related

Curated clinical cross-links plus same-class fallbacks.

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