Co-trimoxazole
Sounds like 'co-tri-mox-a-zole'
Key points about co-trimoxazole
- Co-trimoxazole is an antibiotic used to treat different infections caused by bacteria.
- Co-trimoxazole is also called Trisul® or Deprim®.
- Find out how to take it safely and possible side effects.

Co-trimoxazole is an antibiotic used to treat infections caused by bacteria, such as infections of the urinary tract, skin or chest.
Co-trimoxazole is made up of 2 antibiotics (trimethoprim and sulfamethoxazole). Sulfamethoxazole belongs to a group of antibiotics called sulphonamides.
It works by killing or stopping the growth of bacteria (bugs) which gets rid of the infection. It doesn't work for infections caused by viruses.
In Aotearoa New Zealand co-trimoxazole is available as tablets and liquid and can also be given as an injection in the hospital.
- The dose of co-trimoxazole will be different for different people depending on the type of infection and your age.
- The usual dose for adults is 2 tablets twice a day.
- The dose for children will depend on their body weight. It's usually given 2 times a day.
- Your healthcare provider will advise you about how long to take co-trimoxazole for. It's usually taken for 5 to 7 days, but for urinary tract infections it may only be needed for 3 days.
- Always take your co-trimoxazole exactly as your healthcare provider 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.
Read more about the co-trimoxazole paediatric dose calculator.
- Timing: Co-trimoxazole is usually taken 2 times a day. Try to space the doses evenly throughout the day such as first thing in the morning and at bedtime. Ideally these times should be 12 hours apart.
- Capsules: Swallow the capsules with a drink of water. Don't chew them.
- Liquid co-trimoxazole: Shake the bottle well and use an oral syringe or measuring spoon to measure each dose.
- Food: You can take co-trimoxazole with or without food. If you get a sore tummy, take it with food.
- Missed dose: If you forget to take your dose, take it as soon as you remember. But if it's nearly time for your next dose, take the next dose at the usual time. Don’t take 2 doses at the same time to make up for a forgotten dose.
- Finish the course: It’s best to take the whole course of antibiotics for the number of days your healthcare provider has told you to. You should start to get better after you've been taking co-trimoxazole for a few days. If you don’t feel better or get more unwell, contact your healthcare provider. Don't stop taking it, even if you feel your infection has cleared up.
Here are some things to know when you're taking co-trimoxazole. Other things may be important as well, so ask your healthcare provider what you should know about.
- Alcohol: Co-trimoxazole doesn't directly interact with alcohol. This means that most people can have the occasional drink while taking it without any serious problems. However, if co-trimoxazole makes you feel sick (nausea), don't drink alcohol as it will make you feel worse.
- Driving: Co-trimoxazole can make you feel dizzy. Be careful when driving or using tools until you know how this medicine affects you.
- Other medicines:
- Co-trimoxazole interacts with some medicines, (eg, methotrexate, warfarin, and sulfonylurea medicines for diabetes) herbal supplements and rongoā Māori, so check with your healthcare provider before starting co-trimoxazole and before starting any new products.
- If you're taking the contraceptive pill, you don't need to use additional contraception if you're taking co-trimoxazole. But if you have diarrhoea (runny poo) or vomiting (being sick) that lasts more than 24 hours, absorption of the contraceptive pill may be affected. If you have diarrhoea or vomiting, ask your healthcare provider for advice.
- Pregnancy or breastfeeding: Talk to your healthcare provider if you're pregnant, planning a pregnancy or want to breastfeed.
- Vaccines: Co-trimoxazole may stop the oral typhoid vaccine from working. Have a space of 3 days between the typhoid vaccine and this antibiotic.
Like all medicines, co-trimoxazole can cause side effects, although not everyone gets them. Often side effects improve as your body gets used to the new medicine.
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Read more about medicines and side effects and reporting a reaction you think might be a side effect.
The following links provide further information on co-trimoxazole.
Co-trimoxazole(external link) New Zealand Formulary Patient Information
Trisul(external link) Medsafe Consumer Information Sheet
Brochures
Advice if you are prescribed an antibiotic(external link) BPAC, NZ, 2024
Advice if your child is prescribed an antibiotic(external link) BPAC, NZ, 2024
Medicines and side effects(external link) Healthify He Puna Waiora, NZ, 2024
5 questions to ask about your medications(external link) Health Quality and Safety Commission, NZ, 2019 English(external link), te reo Māori(external link)
Tools
Co-trimoxazole paediatric dose calculator
References
- Trimethoprim + sulfamethoxazole(external link) New Zealand Formulary, NZ
- Trimethoprim + sulfamethoxazole(external link) New Zealand Formulary for children, NZ
- Trisul(external link) Medsafe datasheet, NZ
- Deprim(external link) Medsafe datasheet, NZ
- Interaction reminder – bone marrow suppression with methotrexate and trimethoprim or co-trimoxazole(external link) Medsafe, NZ, 2022
- Appropriate use of sulfonamides(external link) BPAC, NZ, 2012
- Cellulitis – skin deep and spreading across New Zealand(external link) BPAC, NZ, 2015
- Antibiotics – choices for common infections(external link) BPAC, NZ, 2024
Brochures
Advice if your child is prescribed an antibiotic
BPAC, NZ, 2024
Medicines and side effects
Healthify He Puna Waiora, NZ, 2024
Credits: Healthify editorial team. Healthify is brought to you by Health Navigator Charitable Trust.
Reviewed by: Stephanie Yee, Pharmacist, Auckland
Last reviewed: