• Co-trimoxazole is a combination antibiotic which is used to treat specific infections.
  • Take co-trimoxazole at the same times each day to keep a steady level of the medicine in your body.
  • It is important to complete the course prescribed, even if your condition has improved.

About co-trimoxazole

Type of medicine Combination of two different antibiotics
Used for Treatment of certain infections which require this combination of antibiotics
It is not often used to treat simple infections unless there is a good reason for doing so
Also called Septrin®, Septrin® Forte
Available as Tablet, liquid and injection

Co-trimoxazole works by killing the bacteria responsible for causing the infection. Like all antibiotics, those contained in co-trimoxazole only work against certain types of bacteria. This means that co-trimoxazole is only suitable for treating some types of infections.

Before taking co-trimoxazole

Before taking co-trimoxazole make sure your doctor or pharmacist knows:

  • If you are pregnant, trying for a baby or breast-feeding.
  • If you have liver or kidney problems.
  • If you have asthma.
  • If you have any blood disorders including porphyria (a rare blood disorder) or G6PD deficiency (an enzyme deficiency).
  • If you know you have low amounts of the vitamin folic acid.
  • If you are taking other medicines, including those available to buy without a prescription, herbal or complementary medicines.
  • If you have ever had an allergic reaction to this or to any other medicine.

How to take co-trimoxazole

  • Before starting this treatment, read the manufacturer's printed information leaflet from inside the pack.
  • Take co-trimoxazole exactly as your doctor has told you.
  • Try to take co-trimoxazole at the same times each day to keep a steady level of the medicine in your body and to avoid missing any doses. It is usually taken twice each day (in the morning and evening) to treat infections and once a day to prevent infections.
  • If you forget to take a dose, take it as soon as you remember. If you do not remember until the following day, skip the missed dose. Do not take two doses together to make up for a forgotten dose.
  • Keep taking this medicine until the course is finished, unless your doctor tells you to stop. Even if you feel your infection has cleared up, it is important to take the full course to prevent the infection from coming back.

Getting the most from your treatment

  • If you do not notice any improvement after completing your course of co-trimoxazole, make an appointment to see your doctor.
  • Some people develop thrush (a yeast infection which causes redness and itchiness in the mouth or vagina) after taking a course of antibiotics. If you think you have thrush speak to your doctor or pharmacist for advice.
  • If you are using oral combined hormonal contraception (the 'pill'), additional contraceptive precautions such as condoms are not required during a course of this antibiotic unless you are sick or have diarrhoea. If you need further advice, speak with your doctor or pharmacist.
  • If you are having an operation or dental treatment, tell the person carrying out the treatment which medicines you are taking.
  • If you buy any medicines, check with a pharmacist that they are safe to take with your other medicines.

Can co-trimoxazole cause problems?

Along with their useful effects, most medicines can cause unwanted side-effects although not everyone experiences them. These usually improve as your body adjusts to the new medicine, but speak with your doctor or pharmacist if any of the following side-effects continue or become troublesome.

Common side-effects - these affect less than 1 in 10 people who take this medicine What can I do if I experience this?
Feeling sick Eat little and often. Stick to simple foods
Diarrhoea Drink plenty of water to replace any lost fluids
Headache Ask your pharmacist to recommend a suitable painkiller. If the headache continues, speak with your doctor

Important: if you experience any of the following, speak with your doctor immediately or go to your local accident and emergency department without delay.

  • An allergic reaction such as swelling of the mouth, face, tongue or throat with difficulty breathing.
  • Severe skin rash with blisters.
  • High temperature with a sore throat, mouth ulcers or unusual bruising or bleeding.
  • Headache, fever, stiff neck, tiredness, feeling ill and an increased sensitivity to bright light.

If you experience any other symptoms which you think may be due to this medicine, speak with your doctor or pharmacist.

How to store co-trimoxazole

  • Keep all medicines out of the reach and sight of children.
  • Store in a cool, dry place, away from direct heat and light.