Flucloxacillin at a glance
Medicine class
Beta-lactamase-resistant penicillin antibiotic.
Main role
Treats susceptible Gram-positive bacterial infections, especially of the skin and soft tissue.
Available forms
UK products include capsules, oral liquids and injectable preparations.
What is Flucloxacillin used for?
UK products are licensed for infections caused by flucloxacillin-sensitive Gram-positive organisms. The precise indication and suitable formulation depend on the infection and product.
Skin and soft-tissue infections, including cellulitis, abscesses, impetigo, infected wounds, burns and infected skin conditions.
Susceptible respiratory and ear, nose or throat infections, including pneumonia, sinusitis, tonsillitis, pharyngitis and otitis.
Selected oral-solution licences also include susceptible urinary tract infection, enteritis, meningitis and septicaemia.
The selected injectable product is licensed for osteomyelitis, endocarditis, associated or suspected bacteraemia and appropriate peri-operative prophylaxis.
How does Flucloxacillin work?
Flucloxacillin disrupts production of an essential part of the bacterial cell wall, causing susceptible bacteria to break down. It resists many staphylococcal beta-lactamases but is not active against methicillin-resistant staphylococci such as MRSA.
Flucloxacillin preparations and strengths
Capsule
Route: Oral
Strengths: 250 mg, 500 mg
Oral solution
Route: Oral
Strengths: 125 mg/5 mL, 250 mg/5 mL
How to take Flucloxacillin
Follow the prescriber's directions and complete the prescribed course unless a healthcare professional tells you to stop. Oral flucloxacillin should generally be taken on an empty stomach.
Take oral flucloxacillin at least 60 minutes before food or at least 2 hours afterwards.
Swallow capsules whole with a full glass of water and do not lie down immediately afterwards.
Measure liquid with the supplied oral syringe or medicine spoon rather than a kitchen teaspoon.
Shake liquid preparations as directed and follow their label for refrigerated storage and expiry after preparation.
Flucloxacillin side effects
Common or expected effects
- Feeling sick or being sick
- Diarrhoea
- Bloating or indigestion
- Other mild gastrointestinal disturbance
Get urgent medical advice
- Anaphylaxis or angioedema, including breathing difficulty or swelling of the mouth or throat
- Severe, persistent or bloody diarrhoea
- Yellow skin or eyes, dark urine or pale stools suggesting liver injury
- Severe, blistering, peeling or widespread pustular rash
- Unusual bruising, marked pallor or signs of a blood disorder
- Reduced urination, blood in urine or other signs of kidney inflammation
- Severe weakness, cramps or abnormal heart rhythm that could indicate low potassium
Flucloxacillin in pregnancy
Flucloxacillin can be used during pregnancy when recommended by a doctor. Direct pregnancy data are limited, but related penicillins are not known to cause harm, and correctly treating infection is important. Discuss treatment with the prescriber or pharmacist rather than delaying or stopping it without advice.
Flucloxacillin while breastfeeding
Flucloxacillin is generally compatible with breastfeeding because only small amounts enter milk. For a full-term, healthy infant, monitor for poor feeding, vomiting, diarrhoea, oral thrush, rash or possible allergy. Seek specialist advice if the infant is premature or unwell, or if symptoms occur.
Flucloxacillin interactions
Tell the prescriber or pharmacist about all medicines, vaccines and supplements. Important interactions include:
Methotrexate
Flucloxacillin can reduce methotrexate excretion and increase toxicity risk.
Warfarin
The anticoagulant response and INR may change, so additional monitoring may be required when flucloxacillin is started or stopped.
Paracetamol
Concurrent use has rarely been associated with high-anion-gap metabolic acidosis, particularly with severe renal impairment, sepsis, malnutrition or other risk factors.
Voriconazole
Common questions about Flucloxacillin
Answers are fully visible for fast scanning and source review.
What infections does flucloxacillin treat?
It treats susceptible bacterial infections, particularly infections of the skin, wounds, soft tissue, bones and some parts of the respiratory or ear, nose and throat systems. It does not treat viral infections.
Why must capsules be taken with plenty of water?
A full glass of water and remaining upright afterwards reduce the risk of the capsule irritating the oesophagus.
How soon should flucloxacillin start working?
Symptoms often begin improving within a few days. Contact the prescriber if you are not improving after several days or become worse at any time.
Sources
These sources were used to prepare and review this medicine page.
Prepared and reviewed by the iatroX editorial team.