Tablet medication in a tub

Antibiotics work against bacterial infections only. They do not work on viruses which includes most colds and ‘flu’.


  • Antibiotics work in different ways and different types work against different bacteria. The type of antibiotic prescribed will depend on the type of bacteria causing the infection. Antibiotics work by either killing bacteria directly or hamper their ability to grow and reproduce.
  • Most antibiotics are considered ‘broad spectrum’ and are active against both Gram +ve and –ve bacteria.
  • Antibiotics can have side effects; while they're designed to kill the infection-causing bacteria they also kill the ‘good bacteria’ which is required for healthy body. Killing good bacteria is a cause of yeast infections such as thrush.
  • Many antibiotics can cause gastric upsets and skin rashes.
  • Some people may have penicillin allergies which, if true allergies, can be fatal.

Broad spectrum antibiotics are used when the infecting organism is unknown but delays in treatment would worsen the infection. They act against Gram +ve and –ve bacteria. They are used when specific bacteria do not respond to narrow spectrum antibiotics or when there are multiple bacteria causing infection.

Drug names:

  • Amoxicillin.
  • Co- Amoxiclav.
  • Ciprofloxacin.
  • Doxycycline.