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

Flucloxacillin is an antibiotic used to treat infections caused by bacteria.

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

What is flucloxacillin?

Flucloxacillin is an antibiotic used to treat infections caused by bacteria. Examples of infections flucloxacillin may be used for include skin infections such as cellulitis. Flucloxacillin 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. 

For information on how to give amoxicillin to children, see flucloxacillin information for parents and carers. 


In Aotearoa New Zealand flucloxacillin is available as capsules (250 mg and 500 mg) 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.
  • The usual dose of flucloxacillin capsules in adults is 500 mg 4 times a day. Some people may need a higher dose.
  • Your doctor will advise you on how long to take flucloxacillin for (usually 5–7 days).
  • For most infections, you should feel better within a few 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 or at least 2 hours after. This is because your body may absorb less flucloxacillin after a meal, making it less effective.

  • Swallow the capsule with a glass of water (200–250 mLs). Do not chew them.
  • Timing: Take flucloxacillin at the same times each day. Try to space your doses evenly throughout the day. For example, for 4 times a day dosing take, first thing in the morning (before breakfast), at around midday (before lunch), late in the afternoon (before tea) and at bedtime.
  • Missed dose: If you forget to take your dose, take it as soon as you remember. But, if it is nearly time for your next dose, take the next dose at the right time. Do not take extra doses to make up for a forgotten dose. If you are not sure what to do, ask your healthcare provider.
  • Alcohol: You can drink alcohol while taking flucloxacillin. Avoid heavy or binge drinking because it can increase your risk of side effects such as nausea and vomiting. 
  • Complete the course: 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. If you stop your treatment early, your infection could come back.

Possible 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.

Allergic reaction

Tell your healthcare provider if you have had an allergic reaction to a medicine, especially a penicillin antibiotic. True penicillin allergy is rare – fewer than 5 out of 10,000 people are allergic to penicillin.
Most people who think they have a penicillin allergy do not – read more about penicillins and penicillin allergy).

If you develop s
igns of an allergic reaction such as skin rash, itching, swelling of your lips, face and mouth, or difficulty breathing, stop taking amoxicillin and seek immediate medical attention. 

Other side effects

Side effects What should I do?
  • Nausea (feeling sick)
  • Stomach upset
  • It is quite common to feel sick (nausea) when you take flucloxacillin
  • 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.
  • Tell your doctor if these side effects bother you. If you are taking high doses, your doctor may advise to take flucloxacillin with food to lessen these effects.
  • Diarrhoea (runny poos)
  • This should settle after a few days.
  • Drink plenty of fluids such as water or squash to avoid dehydration.
  • Tell your doctor if it bothers you.
  • 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
  • These can occur up to 2 months after you have stopped taking flucloxacillin and are more common with courses longer than 2 weeks and for older people.
For more information on side effects, see the Medsafe consumer information leaflets below.

Did you know that you can report a medicine side effect to the Centre for Adverse Reactions Monitoring (CARM)? Report a side effect to a product.

Learn more

The following links have more information on flucloxacillin:

NZ Formulary, NZ

Medsafe Consumer Information, NZ
Flucloxacillin (AFT) 


  1. Flucloxacillin NZ Formulary, NZ
  2. Antibiotics – choices for common infections BPAC, NZ, 2021

Additional resources for healthcare professional

Antibiotics – the future is short BPAC, NZ, 2018
When is an allergy to an antibiotic really an allergy? BPAC, NZ, 2015

Credits: Sandra Ponen, Pharmacist. Reviewed By: Maya Patel, MPharm PGDipClinPharm, Auckland Last reviewed: 12 Feb 2022