Flucloxacillin
A narrow-spectrum penicillin for Staph aureus infections: cellulitis, impetigo, abscesses, septic arthritis and osteomyelitis.
On this page
Uses
- Cellulitis, erysipelas (often with or instead of penicillin).
- Impetigo (widespread), infected eczema, wound infections.
- Septic arthritis, osteomyelitis.
Adult dose
| Route | Dose |
|---|---|
| Oral | 500 mg–1 g 4 times daily, on an empty stomach |
| IV | 1–2 g every 6 hours (up to 2 g every 4 hours in endocarditis or osteomyelitis per specialist) |
Children's dose
| Route | Dose |
|---|---|
| Oral | 12.5–25 mg/kg 4 times daily (max 500 mg–1 g per dose) |
| IV | 25–50 mg/kg every 6 hours (max 2 g per dose) |
Kidney and liver
- Severe kidney impairment: reduce dose.
- Cholestatic jaundice can occur, even weeks after stopping, especially in the elderly and with long courses.
Pregnancy and breastfeeding
Considered safe.
Side effects and cautions
- Diarrhoea, rash.
- Penicillin allergy: avoid.
Frequently asked questions
Should flucloxacillin be taken with food?
No. Take it on an empty stomach, at least 1 hour before or 2 hours after food.
What is the flucloxacillin dose for cellulitis?
500 mg to 1 g four times a day for 5–7 days orally, or 1–2 g IV every 6 hours if severe.
Used in these guides
Sources
Doses on this page are typical doses from the sources above. Always confirm with a current drug reference, the product leaflet and your hospital protocol, especially in children, pregnancy and kidney or liver disease.
For FCPS Part 1
Revising for FCPS Part 1? Flucloxacillin is covered in our textbook chapter Antimicrobials in pregnancy, with practice MCQs.