Sounds like 'co-tri-mox-a-zole'

Easy-to-read medicine information about co-trimoxazole – what it is, how to take co-trimoxazole safely and possible side effects.

Type of medicine

Also called

  • Antibiotic (to treat infections)
  • Sulphur antibiotic 
  • Trisul Tablet®
  • Deprim oral liquid

What is co-trimoxazole?

  • Co-trimoxazole is an antibiotic that is used to treat infections such as bladder infections, skin infections, or chest infections. 
  • It works by killing or stopping the growth of bugs that cause infection. It is one of a group of antibiotics known as sulphonamides.
  • Co-trimoxazole is made up of two antibiotics (trimethoprim  and sulfamethoxazole).

How to take co-trimoxazole

  • The usual dose of co-trimoxazole is two tablets twice daily.  The dose for children is based on their weight and age.
  • Depending on the type of infection, your doctor will advise you on how long to take co-trimoxazole for (usually between 5 to 10 days).
  • Take co-trimoxazole at the same time each day, in the morning and in the evening.
  • You can take co-trimoxazole with or without food. If you get stomach upset, try taking it with food.
  • Keep taking co-trimoxazole until you finish all the tablets or medicine, for as long as your doctor or pharmacist tells you.
  • Do not stop taking co-trimoxazole, even if you feel better after a few days, unless your doctor tells you to.
  • If you forget to take trimoxazole, take it as soon as you remember.
  • But, if it is nearly time for your next dose, just take the next dose at the right time. Do not take double the dose.

Possible side effects

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

Side effects What should I do?
  • Nausea (feeling sick) or vomiting
  • Try taking co-trimoxazole with food.
  • Diarrhoea (loose, watery stools)
  • This may settle after a few days.
  • Tell your doctor if troublesome.
  • 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 co-trimoxazole.
  • Tell your doctor immediately or ring HealthLine.


Co-trimoxazole may interact with a few medications and herbal supplements, so check with your doctor or pharmacist.

Learn more

Medsafe Consumer Information Sheet Trisul

Credits: Sandra Ponen, Pharmacist. Reviewed By: Dr J Bycroft. Health Navigator NZ Last reviewed: 26 Jun 2014