Sounds like 'flu-CLOX-i-SIL-in'

Flucloxacillin is an antibiotic used to treat different infections caused by bacteria. Find out how to take it safely and possible side effects.

Type of medicine Also called
  • Antibiotic (to treat infections)
  • Penicillin antibiotic 
  • Staphlex®
  • Flucloxacillin (AFT)®

What is flucloxacillin?

Flucloxacillin is an antibiotic used to treat bacterial infections, such as ear infections and skin infections including cellulitis. It works by killing or stopping the growth of bacteria (bugs). Flucloxacillin belongs to a group of antibiotics called penicillins. Like all antibiotics, flucloxacillin is not effective against infections caused by viruses. In New Zealand, flucloxacillin is available as capsules and liquid and can be given as an injection in the hospital.


  • The dose of flucloxacillin will be different for different people depending on the type of infection and your age.
  • Adults: the usual dose is 250 mg or 500 mg three or four times a day. 
  • Children: the dose for children will depend on their body weight. It is usually given 4 times a day.
  • Your doctor will advise you on how long to take flucloxacillin for (usually 5 to 7 days).
  • Always take your flucloxacillin exactly as your doctor has told you. The pharmacy label on your medicine will tell you how much to take, how often to take it, and any special instructions. 

How to take flucloxacillin

Flucloxacillin is best taken on an empty stomach, one hour before eating food. This is because your body may absorb less flucloxacillin after a meal, making it less effective.

  • Capsules: swallow the capsule with a glass of water. Do not chew them.
  • Liquid: shake the medicine well. Measure the right amount using an oral syringe or medicine spoon. You can get these from your pharmacy. Do not use a kitchen spoon as it will not give you the right amount. Read more: Tips on how to give medicines to babies and children.
  • Timing: Take flucloxacillin at the same times each day. Try to space your doses evenly throughout the day.
    • Three times each day: this should be in the morning, early afternoon and at bedtime.
    • Four times each day: this should be about 4 hours apart, for example 7am, 11am, 3pm and 7pm. 
  • Missed dose: If you forget to take your dose at the correct time, take one as soon as you remember. Try to take the correct number of doses each day. Do not take two doses at the same time to make up for a forgotten dose.
  • If you are sick: If you are sick (vomit) less than 30 minutes after having a dose of flucloxacillin, take the same dose again. But, if you are sick (vomit) and it is more than 30 minutes after having a dose of flucloxacillin, you do not need to take another dose. Wait until the next normal dose. If you are vomiting and are worried, contact your doctor or Healthline (0800 611 116) for advice.

Other tips

  • Store your capsules in a cool, dry place, away from direct heat and light. If you have been given liquid medicine, this will have been made up by the pharmacy and you may need to keep it in the fridge - check the instructions on the bottle. Make sure the medicine does not freeze.
  • It is best to take the whole course of antibiotics for the number of days your doctor has told you to. Do not stop taking it, even if you feel your infection has cleared up.

Precautions before starting flucloxacillin

  • Have ever had an allergic reaction to a medicine, especially a penicillin antibiotic?
    (Note, 9 out of 10 people who think they have a penicillin allergy do not – read more about penicillins and penicillin allergy)
  • Do you have problems with your liver?
  • Are taking any other medicines? This includes any medicines you are taking which you can buy without a prescription, as well as herbal and complementary medicines.

If so, it’s important that you tell your doctor or pharmacist before you start flucloxacillin. Sometimes a medicine isn’t suitable for a person with certain conditions, or it can only be used with extra care.

What are the side effects of flucloxacillin?

Like all medicines, flucloxacillin can cause side effects, although not everyone gets them. Often side effects improve as your body gets used to the new medicine.

Side effects What should I do?
  • Nausea (feeling sick)
  • Stomach upset
  • It is quite common to feel sick (nausea) when you take flucloxacillin
  • Tell your doctor if troublesome. If you are taking high doses, your doctor may advise to take flucloxacillin with food to lessen these effects.
  • Diarrhoea (runny poos)
  • These may go away with time.
  • Tell your doctor if troublesome. If you are taking high doses, your doctor may advise to take flucloxacillin with food to lessen these effects.
  • Vaginal itching, soreness or discharge (thrush)
  • Tell your doctor or pharmacist.
  • Allergic reaction such as skin rash, itching, swelling of the lips, face, and mouth or difficulty breathing
  • Stop taking flucloxacillin.
  • Tell your doctor immediately or ring HealthLine 0800 611 116
  • Signs of problems with your liver such as yellowing of the skin or eyes, dark urine, pain in the abdomen.
  • Tell your doctor immediately or ring HealthLine 0800 611 116
  • This can occur even after you have stopped taking flucloxacillin.


Flucloxacillin may interact with a few medications and herbal supplements, so check with your doctor or pharmacist before starting flucloxacillin or before starting any new medicines. If you are taking the contraceptive 'pill', the effectiveness of the 'pill' can be reduced if you have a bout of being sick (vomiting) or diarrhoea which lasts for more than 24 hours. If this happens, ask your doctor or pharmacist for advice about contraception over the following few days.

Learn more

The following links have more information on flucloxacillin:

New Zealand Formulary Patient Information

Medsafe Consumer Information Sheet
Flucloxacillin (AFT) 


  1. Flucloxacillin New Zealand Formulary
  2. Antibiotics: choices for common infections BPAC, 2017
Credits: Sandra Ponen, Pharmacist. Reviewed By: Angela Lambie, Pharmacist, Auckland Last reviewed: 05 Apr 2019