Key points about antibiotics

  • Antibiotics (or antibacterials) are a group of medicines used to treat bacterial infections.
  • Inappropriate use of antibiotics can cause antibiotic resistance.
  • Find out antibiotics and possible side effects.


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Antibiotics (or antibacterials) are a group of medicines that treat bacterial infections. In the past, other substances were found to kill bacteria, but many of these, such as mercury, were almost as dangerous to our own cells as the bacteria. 

Antibiotics work because bacteria have certain differences from human cells, so they can kill the bacteria without hurting us.

Examples of antibiotics used in New Zealand 

Antibiotic resistance

In just a few short decades, the misuse and overuse of antibiotics have allowed some bacteria to genetically mutate to resist these medicines. This is called antibiotic resistance. If bacteria become resistant to antibiotics, this means the antibiotics stop working – this is a serious threat to everyone’s health. Some bacteria, or 'super bugs', are now resistant to all known antibiotics and can't be treated easily. 

Read more about antibiotic resistance.

In Aotearoa New Zealand, most antibiotics are available only with a prescription.

  • They should be taken only as prescribed to treat bacterial infections that your natural immune system is having difficulty fighting off.
  • Antibiotics are not usually recommended for infections like colds, coughs, flu and most ear, nose and throat infections, where they won’t make you get better any faster. If you have generally good health, your body’s immune system can easily fight these infections without antibiotics.
  • Antibiotics are normally only prescribed for more serious infections caused by bacteria, eg, pneumonia, whooping cough and meningococcal disease. In these situations, antibiotics can be lifesaving.
  • You should always take antibiotics according to the instructions, and complete the entire course even if you’re feeling better.

Unless you have been prescribed antibiotics as an early treatment for a chronic chest problem, you shouldn't have antibiotics sitting around in your medicine cabinet. You should never take antibiotics that are left over from another illness or have been prescribed for another person.

Antibiotics are not effective against viruses                                                  

  • Antibiotics are no help against illnesses caused by a virus, eg, the common cold and flu.
  • Taking antibiotics unnecessarily for viral illnesses may increase the risk of bacteria developing resistance.

Different antibiotics affect people differently, but side effects include diarrhoea, nausea, vomiting and fungal infections. Many of these effects can be reduced by taking the medicine as directed, such as after a full meal or with a full glass of fluid.

  • A small number of people might have a severe allergic reaction to some groups of antibiotics, eg, penicillins.
  • Always tell your doctor if you have had an allergic reaction to an antibiotic in the past. Describe the reaction and, if you can, tell them the name of that antibiotic.
  • Care also needs to be taken if you have liver or kidney problems, if you're taking other medicines or you're pregnant or breastfeeding.
  • Some antibiotics need to be taken with food.
  • Some don’t mix well with alcohol, while others affect certain other medicines, such as the anticoagulant warfarin.

That’s why it’s important to follow the instructions carefully.

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Credits: Sandra Ponen, Pharmacist, Healthify He Puna Waiora. Healthify is brought to you by Health Navigator Charitable Trust.

Reviewed by: Angela Lambie, Pharmacist, Auckland

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