Flucloxacillin

Generic name

Flucloxacillin

Active ingredient

Flucloxacillin

Product type

Small-molecule medicine

Drug class

Penicillins

Brand names

UK · US

Routes

Oral, Intravenous

Dosage forms

Capsule, Solution, Injection

Also known as

floxacillin

Usual preparations

Capsules; the NHS also describes a liquid for children and people who struggle with capsules, and an injection given in hospital. (summary of the cited reference, not a prescription)

Onset and duration

The NHS says most infections should improve within a few days.

Monitoring

NHS England pharmacy directions say people taking warfarin or similar anticoagulants should be advised to have their INR monitored during treatment, because rises in INR have been reported.

Availability by country

Legal status differs between countries and can change; each row cites the document it was taken from and applies only to the country named.

What it is used for

• Skin and wound infections
• Bone infections (osteomyelitis)
• Ear infections
• Impetigo and infected insect bites, which community pharmacists in England can supply it for under NHS patient group directions

How it works in the body

Flucloxacillin kills the bacteria that cause the infection. As a penicillin, it works by damaging the cell wall that bacteria need to survive, which human cells do not have.

Cautions and interactions

• The NHS lists a past allergic reaction to flucloxacillin, another penicillin-type antibiotic or any other medicine as a reason to check with a doctor or pharmacist first.
• People with liver or kidney problems, and people who have recently had or are due a vaccination, are also listed for checking first.
• Liver injury such as jaundice or hepatitis is a recognised risk; the NHS formulary says it is higher with longer courses and increasing age.
• It can make the oral typhoid vaccine less effective.
• Medicines to check about include methotrexate, warfarin, gout medicines such as probenecid, voriconazole and other antibiotics.
• There is not enough information to say herbal remedies and supplements are free of interaction with it.
• Very rarely, taking it with paracetamol has been linked to a blood and fluid imbalance (high anion gap metabolic acidosis).
• The NHS says alcohol can be drunk while taking it.

Interactions

Interactions documented in the official sources cited on each card. The list covers the medicines represented on this site and is not exhaustive; how the interaction data is compiled.

No pair records for this medicine are in the sources currently represented by Anatomy Nexus. Absence from this list does not mean no interaction exists.

Same-class and related medicines

Same class: Penicillins

Medicines that share the class of Flucloxacillin. They are separate medicines with their own licences, doses and interactions, not alternative names for Flucloxacillin.

Related medicines

Medicines often discussed alongside Flucloxacillin: used together, compared with it, or acting on the same problem by a different route.

Key facts

What is flucloxacillin used for?

Flucloxacillin is a penicillin-type antibiotic, and the NHS says it is available only on prescription. It is used to treat infections of the skin and wounds, bone infections known as osteomyelitis, and ear infections. In England, community pharmacists can also supply it for some skin problems, such as impetigo and infected insect bites, under NHS patient group directions. The NHS says most infections should improve within a few days. It also says that carrying on until the prescribed course is finished matters even when a person feels better, because stopping early could let the infection return.

How does flucloxacillin work?

According to the NHS, flucloxacillin works by killing the bacteria that cause the infection. As a penicillin, it acts on the cell wall that bacteria need to stay intact, a structure human cells do not have. It belongs to the same family as other penicillin antibiotics. This shared family is why the NHS asks about any past allergic reaction to a penicillin-type antibiotic before it is used. UK patient leaflets say it should not be taken by people with an allergy to penicillin or other antibiotics of the same kind. The leaflets describe swelling of the face, lips, throat or tongue, breathing problems and an itchy rash as signs of a severe allergic reaction, and say to stop the medicine and contact a doctor at once. The NHS says swelling of the lips, mouth, throat or tongue, severe breathing difficulty or fainting is an emergency that needs a 999 call.

Taking flucloxacillin

The NHS describes flucloxacillin as best absorbed on an empty stomach, meaning it is taken before eating or a good while after a meal or snack. Capsules are swallowed whole with a full glass of water, and the NHS advises against lying down straight after. The medicine comes as capsules, and the NHS also describes a liquid for children and people who struggle with capsules, and an injection that hospitals can give. The NHS says to carry on until the course is finished even when a person feels better, because stopping early could let the infection return. The NHS says alcohol can be drunk during treatment. Dosing details are on the NHS medicine page and in the patient leaflet, so they are not given here.

Who needs extra care?

The NHS says most adults and children can take flucloxacillin, with a few exceptions to check first. These include a past allergic reaction to flucloxacillin, another penicillin-type antibiotic or any other medicine. People with liver or kidney problems, and those who have recently had or are due a vaccination, are also on the list. In pregnancy the NHS says it can be taken, but a pharmacist or doctor is asked first. For breastfeeding, the NHS says only tiny amounts pass into breast milk, so side effects in the baby are unlikely. The NHS page lists poor feeding, vomiting, diarrhoea, oral thrush or a rash in the baby as signs to look out for and to get advice about.

Side effects and the warning about the liver

The NHS says common side effects, affecting more than 1 in 100 people, are feeling sick, diarrhoea, bloating and indigestion. Simple meals and small sips of fluid are suggested to avoid dehydration, and being sick or having severe diarrhoea can make the contraceptive pill less reliable. Serious side effects are rare, affecting fewer than 1 in 10,000 people according to the NHS. They include yellowing of the skin or eyes with pale stools and dark urine, which can point to liver problems. UK leaflets describe jaundice and hepatitis, meaning liver inflammation, as effects that can be delayed for up to two months after treatment ends. An NHS formulary says the liver risk is higher with longer courses and with increasing age. Diarrhoea with blood or mucus, blistering or peeling skin and unusual bruising are also warning signs. For these, a GP or NHS 111 is the route to care, and some can appear after the course has finished. Anaphylaxis is rare but an emergency, with swelling of the lips, mouth, throat or tongue, severe breathing difficulty or fainting needing a 999 call.

Taking it with other medicines

The NHS says some medicines can change how flucloxacillin works or raise the chance of side effects. Examples it names are methotrexate, warfarin, gout medicines such as probenecid, voriconazole and other antibiotics. Flucloxacillin can make the oral typhoid vaccine less effective, so a doctor is told about a recent or planned vaccine. NHS England pharmacy directions note that rises in INR have been reported with warfarin and similar anticoagulants, and that INR should be monitored. Very rarely, a blood and fluid imbalance called high anion gap metabolic acidosis has been reported when it is taken with paracetamol. The NHS says there is not enough information to say herbal remedies and supplements are free of interaction, partly because they are usually not tested for their effect on other medicines. The NHS lists are examples only, and the leaflet in the pack has the full list.

Frequently asked questions