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  1. About flucloxacillin
  2. Key facts
  3. Who can and can't take flucloxacillin
  4. How and when to take it
  5. Side effects
  6. How to cope with side effects
  7. Pregnancy and breastfeeding
  8. Cautions with other medicines
  9. Common questions

1. About flucloxacillin

Flucloxacillin is an antibiotic.

It's used to treat skin and wound infections, chest infections, such as pneumonia, and bone infections (osteomyelitis).

Flucloxacillin is used in children, often to treat ear infections and chest infections.

The medicine is available only on prescription. It comes as capsules or as a liquid that you drink. It can also be given by injection, but this is usually done in hospital.

2. Key facts

  • Take flucloxacillin on an empty stomach. This means 30 to 60 minutes before a meal or snack, or at least 2 hours after.
  • For most infections, you should feel better within a few days.
  • The most common side effects are feeling sick (nausea) and diarrhoea.
  • You can drink alcohol while taking flucloxacillin.
  • Flucloxacillin is called by the brand name Floxapen.

3. Who can and can't take flucloxacillin

Flucloxacillin can be taken by adults, including pregnant and breastfeeding women.

Flucloxacillin can be taken by children.

To make sure flucloxacillin is safe for you, tell your doctor if you:

  • have had an allergic reaction to penicillin, flucloxacillin or any other medicines in the past
  • have liver or kidney problems
  • have recently had, or are about to have, any vaccinations

4. How and when to take it

The usual dose of flucloxacillin is 250mg to 500mg taken 4 times a day. In children, the dose may be lower.

It's best to take flucloxacillin on an empty stomach. This means 30 to 60 minutes before a meal or snack, or at least 2 hours after.

Try to space your doses evenly throughout the day. For example, first thing in the morning (before breakfast), at around midday (before lunch), late in the afternoon (before tea) and at bedtime.


Carry on taking this medicine until you've completed the course, even if you feel better. If you stop your treatment early, your problem could come back.

How to take it

Swallow flucloxacillin capsules whole with a drink of water. Do not chew or break them.

There's a liquid flucloxacillin available for children and people who find it difficult to swallow tablets.

If you or your child are taking flucloxacillin as a liquid, it'll usually be made up for you by your pharmacist. The medicine will come with a syringe or spoon to help you take the right amount. If you don't have a syringe or spoon, ask your pharmacist for one. Do not use a kitchen teaspoon as it will not give you the right amount.

What if I forget to take it?

If you forget to take a dose, take 1 as soon as you remember, unless it's nearly time for your next dose. In this case, just leave out the missed dose and take your next dose as normal.

Never take 2 doses at the same time. Never take an extra dose to make up for a forgotten one.

If you forget doses often, it may help to set an alarm to remind you. You could also ask your pharmacist for advice on other ways to help you remember to take your medicine.

What if I take too much?

Try to take the correct number of doses each day, leaving at least 3 hours between doses.

Taking an extra dose of flucloxacillin by accident is unlikely to harm you or your child.

Talk to your pharmacist or doctor if you're worried or if you take more than 1 extra dose.

5. Side effects

Like all medicines, flucloxacillin can cause side effects in some people, although not everyone will get them.

Common side effects

These common side effects of flucloxacillin happen in more than 1 in 100 people. Keep taking the medicine, but tell your doctor or pharmacist if these side effects bother you or don't go away:

  • feeling sick (nausea)
  • being sick (vomiting) and diarrhoea
  • bloating and indigestion

Serious side effects

Serious side effects are rare and happen to less than 1 in 1,000 people.

Call a doctor straight away if you get:

  • diarrhoea (possibly with muscle cramps) that contains blood or mucus. If you have severe diarrhoea without blood or mucus for more than 4 days you should also speak to a doctor.
  • pale poo with dark pee, yellowing of the whites of the eyes and skin - this can be a sign of liver problems
  • bruising or discoloured skin
  • joint or muscle pain that comes on after 2 days of taking the medicine

Some of these serious side effects may not happen for up to 2 months after finishing the course of flucloxacillin.

Serious allergic reaction

In rare cases, it's possible to have a serious allergic reaction (anaphylaxis) to flucloxacillin.

Immediate action required: Call 999 or go to A&E if:

  • you get a skin rash that may include itchy, red, swollen, blistered or peeling skin
  • you're wheezing
  • you get tightness in the chest or throat
  • you have trouble breathing or talking
  • your mouth, face, lips, tongue or throat start swelling

You could be having a serious allergic reaction and may need immediate treatment in hospital.

These are not all the side effects of flucloxacillin. For a full list see the leaflet inside your medicines packet.


You can report any suspected side effect to the UK safety scheme.

6. How to cope with side effects

What to do about:

  • feeling sick (nausea) - stick to simple meals and try not to eat rich or spicy food
  • being sick (vomiting) and diarrhoea - drink lots of fluids such as water or squash - take small, frequent sips if you are being sick to avoid dehydration. Signs of dehydration include peeing less than usual or having strong-smelling pee. Do not take any other medicines without speaking to a pharmacist or doctor.
  • bloating and indigestion - try not to eat foods that cause wind (like lentils, peas, beans and onions). Eat smaller meals, eat and drink slowly, and exercise regularly. Pharmacy medicines like simethicone can also help.

7. Pregnancy and breastfeeding

It's usually safe to take flucloxacillin during pregnancy and while breastfeeding.


For safety, tell your doctor if you're trying to get pregnant, are already pregnant or if you're breastfeeding.

8. Cautions with other medicines

There are some medicines that don't mix well with flucloxacillin.

Tell your doctor if you're taking these medicines before you start flucloxacillin:

  • methotrexate
  • a blood thinner called warfarin
  • other antibiotics

You should also let your doctor know if you've recently had, or are about to have, any vaccinations.

Mixing flucloxacillin with herbal remedies and supplements

There are no known problems with taking herbal remedies and supplements with flucloxacillin.


For safety, tell your doctor or pharmacist if you're taking any other medicines, including herbal remedies, vitamins or supplements.

9. Common questions

How does flucloxacillin work?

Flucloxacillin is one of a group of antibiotics called penicillins. It works by damaging the cell walls of bacteria and killing them.

When will I feel better?

For most infections, you should feel better within a few days.

It's very important that you continue taking flucloxacillin until you've finished the course. Do this even if you feel better. It'll help stop the infection coming back.

What if I don't get better?

Tell your doctor if you don't start feeling better after taking flucloxacillin for 3 days. Also tell them if, at any time, you start to feel worse.

Will it give me thrush?

Some people get a fungal infection called thrush after taking a course of antibiotics like flucloxacillin. It happens because antibiotics kill the normal harmless bacteria that help to protect you against thrush.

Ask your pharmacist or doctor for advice if this happens to you.

Will it affect my contraception?

Flucloxacillin doesn't stop contraceptive pills working, including the combined pill or emergency contraception.

However, if flucloxacillin makes you vomit or have severe diarrhoea (6 to 8 watery poos in 24 hours) for more than 24 hours, your contraceptive pills may not protect you from pregnancy. Look on the pill packet to find out what to do.

Read more about what to do if you're on the pill and you're being sick or have diarrhoea.

Will it reduce my fertility?

There's no firm evidence to suggest that taking flucloxacillin will reduce fertility in either men or women.

Can I drive or ride a bike?

Yes, flucloxacillin shouldn't affect you being able to drive or cycle.

Can I drink alcohol with it?

Yes, you can drink alcohol while taking flucloxacillin.

Is there any food or drink I need to avoid?

You don't need to avoid any foods or drinks while taking flucloxacillin. However, make sure to take it on an empty stomach.