Antibiotics
Key facts
- Antibiotics are medicines that treat infections and diseases caused by bacteria.
- All antibiotics damage bacteria so that your immune system can more easily fight the bacteria.
- Doctors prescribe antibiotics that are best suited to treat the type of infection you have.
- Antibiotics can cause side effects and allergies.
- Because antibiotics have been overused, many no longer work.
What are antibiotics?
Antibiotics are medicines that treat infections and diseases caused by bacteria. Penicillin is a well-known antibiotic.
Antibiotics do not work against viruses, which are the cause of most colds, flu and COVID-19.
How do antibiotics work?
Antibiotics work by killing the bacteria or stopping them from multiplying. This helps your immune system to fight the infection.
Why are there different types of antibiotics?
Some antibiotics work against different types of bacteria:
- Broad-spectrum antibiotics — such as amoxicillin — work against many types of bacteria.
- Narrow-spectrum antibiotics — such as penicillin — only work against a few types of bacteria.
Your doctor will choose an antibiotic that is best suited to treat your infection.
How do doctors know which antibiotics to use?
Sometimes, your doctor will choose an antibiotic based on what is likely to work.
At other times, your doctor will suggest you have tests. These will show which types of bacteria are causing your infection. This information helps them to choose the antibiotics that will be most effective.
What are the side effects of antibiotics?
Like all medicines, antibiotics can cause side effects.
Some common side effects are:
Less common side effects are:
- ongoing diarrhoea
- allergic reactions — most often skin reactions
There is some evidence that taking probiotics during a course of antibiotics can reduce antibiotic-associated diarrhoea. Probiotics are available in supermarkets, pharmacies and health food stores.
Ask your doctor or pharmacist about possible side effects from your medicine.
What happens if I'm allergic to antibiotics?
If you suspect you are having an anaphylactic reaction, call triple zero (000) for an ambulance.
If you are allergic to a type of antibiotics, your immune system overreacts to that antibiotic. You may get symptoms like:
- hives (a rash and itchy skin)
- a fever — a temperature of 38°C or higher
- difficulty breathing
A severe allergy may result in anaphylaxis and usually happens within an hour of taking the antibiotic. This is a medical emergency and needs immediate medical attention.
Feeling nauseous and vomiting after taking antibiotics are common side-effects. These are not an allergic reaction.
Many people think they are allergic to antibiotics, especially penicillin. But in most people antibiotic allergies disappear after a few years.
It's important to talk about your antibiotic allergy with your doctor or pharmacist. They can help you take the right antibiotics safely, when you need them.
How do I take antibiotics?
Like all medicines, when taking antibiotics you should follow the instructions that your doctor or pharmacist gives you. You should:
- take your antibiotics at the right time
- take them for as long as you are told to, even if you are feeling better
- do not take more than you have been told to (even if there are tablets left)
- return tablets that you don't use to the pharmacy
Do not share antibiotics with other people.
Most antibiotics are given by mouth, either as a liquid or a tablet. Some antibiotics can be put directly in your eyes as eye drops or ointment.
If you are in hospital, you might be given antibiotics through a drip (intravenously). Your doctor will choose the best way for you to get your medicine.
You might want to ask your doctor if there are any medicines you should not take with your antibiotics. This information can also be found in the Consumer Medicine Information (CMI) that comes with your medicine.
What should I do if I cannot get my antibiotics?
The COVID-19 pandemic has changed the supply chain of many medicines, including antibiotics.
If you cannot get the medicine that you need, speak to your pharmacist or doctor. They can advise on alternatives.
For more information, visit Therapeutic Goods Administration (TGA).
What is antibiotic resistance?
Antibiotic resistance happens when bacteria change to protect themselves from an antibiotic. This means that the antibiotic no longer works to kill the bacteria.
This can happen naturally. But the main cause of antibiotic resistance is antibiotic use.
Antibiotic resistance can happen by:
- using antibiotics when they're not needed
- not taking antibiotics properly — such as missing doses or not finishing the course
Antibiotic resistance means that some bacterial infections may cause serious illness or death.
What are 'superbugs'?
'Superbugs' is a term used for bacteria that are resistant to many types of antibiotics. These infections are very hard to treat.
Examples of superbugs are:
- methicillin-resistant Staphylococcus aureus (MRSA)
- multi-resistant gram-negative bacilli (MRGN)
- vancomycin-resistant enterococci (VRE)
The last antibiotic treatment for gonorrhoea has already started to fail in Australia.
What happens if I get an antibiotic-resistant infection?
If you get an antibiotic-resistant infection:
- you will be sick for longer
- you may get more complications from the infection
- you may need more complex care
- you might be infectious for longer so may pass your infection on to other people
How can I help prevent antibiotic resistance?
Australia has one of the highest rates of antibiotic use in the world. You can help slow down antibiotic resistance by:
- not asking for antibiotics when you have a cold or the flu — antibiotics do not treat viral infections
- taking the antibiotics as prescribed by your doctor, for as long as you need them
- having good hygiene practices to help stop the spread of infections
Antibiotic resistance can't be totally stopped, but you can help slow it down by using antibiotics sensibly.
Why did I get antibiotics when I had surgery?
Sometimes antibiotics are prescribed to stop infections happening. This might happen when you have surgery or a dental procedure.
In Australia, doctors and nurses are working together to review this practice. By lowering the use of antibiotics, they will help lower antibiotic resistance.
Resources and support
Learn more about antimicrobial resistance.
Learn about the safe use of antibiotics on the Australian Commission on Safety and Quality in Health Care website.
You can call 1300 MEDICINE (1300 633 424) if you have questions about your medicines.
The Health Translations website has information about antibiotic resistance in languages other than English.
The National Antibiotic Allergy Network has information on antibiotic allergies and side effects in languages other than English.
You can also call healthdirect on 1800 022 222 (known as NURSE-ON-CALL in Victoria). A registered nurse is available to speak with, 24 hours, 7 days a week.
Learn more here about the development and quality assurance of healthdirect content.
Last reviewed: September 2024
