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Brand Name(s) : Septrin
Side Effects


Co-trimoxazole should be used with caution in: the elderly, infants under 6 weeks of age, pregnant women and women who are breastfeeding, those with asthma, severe allergy, kidney or liver problems, blood disorders, or those who are deficient in the enzyme called glucose-6-phosphate dehydrogenase (common in peoples from Africa, Asia, Oceania and Southern Europe).

It should not be used in: people with severe liver problems or severe kidney problems, or those with a blood disorder called acute porphyria.

Also see list of precautions and interactions.


Protect from light and do not store above 25°C.


What is it used for?

  • Co-trimoxazole is used to treat a number of problems.
  • It is a mixture of two drugs: trimethoprim and sulfamethoxazole, and is sometimes known as an antibiotic.
  • It is used to treat infections caused by bacteria in many different parts of the body.
  • In general this drug is used to treat infections of the respiratory tract, middle ear, urinary tract, and conditions such as toxoplasmosis (a parasitic disease caused by the protozoan Toxoplasma gondii) and nocardiosis (a serious infectious disease affecting either the lungs or the whole body owing to infection by the Nocardia bacterium).
  • Benefits of being on this drug can include eradication and resolution of bacterial infections, allowing recovery and relief of symptoms such as pain or cough caused by the infection.

Listed below are the typical uses of co-trimoxazole.

On occasion your doctor may prescribe this medicine to treat a condition not on the above list.


How often do I take it?

  • Take this medication by mouth, usually twice daily, preferably with food. Tablets should be taken with a glass of water. It is also available as an oral suspension to be taken by mouth and as a liquid for intravenous infusion (when given by a doctor or other healthcare worker).
  • Use this medication for the duration of the prescription in order to get the most benefit from it.
  • Remember to use it at the same time each day - unless specifically told not to by your doctor.
  • It may take some time before the full benefit of this drug takes effect.
  • Certain medical conditions may require different dosage instructions as directed by your doctor.

What dose?

  • Dosage is based on your age, gender, medical condition, response to therapy, and use of certain interacting medicines.

Do I need to avoid anything?

  • None known. Consult your doctor or pharmacist for more details.

When can I stop?

  • Always complete the full course as prescribed by your doctor.


If any of these persist or you consider them severe then inform your doctor or pharmacist.

Tell your doctor immediately if you develop any of the following symptoms: heart problems, yellowing of the skin or eyes (jaundice), increased sensitivity to light (photosensitivity).

Remember that your doctor has prescribed this medication because he or she has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.

A serious allergic reaction to this drug is unlikely, but seek immediate medical attention if it occurs. Symptoms of a serious allergic reaction include: rash, itching/swelling (especially of the face/tongue/throat), dizziness, trouble breathing.

This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.

The Yellow Card Scheme allows you to report suspected side effects from any type of medicine (which includes vaccines, herbals and over the counter medicines) that you are taking. It is run by the medicines safety watchdog called the Medicines and Healthcare products Regulatory agency (MHRA). Please report any suspected side effect on the Yellow Card Scheme website.


Before taking co-trimoxazole, tell your doctor or pharmacist if you are allergic to it; or to other antibiotics; or if you have any other allergies.

This medication should not be used if you have certain medical conditions. Before using this medicine, consult your doctor or pharmacist in case of: a blood disorder called acute porphyria.

Before using this medication tell your doctor or pharmacist your medical history, especially any of the following: a history of asthma, severe allergy, any kidney or liver problems, blood disorders, or if deficient in the enzyme called glucose-6-phosphate dehydrogenase (common in peoples from Africa, Asia, Oceania and Southern Europe).

Before having surgery, tell your doctor or dentist that you are taking this medication.

Does alcohol intake affect this drug?

  • It is not known whether drinking alcohol affects this drug's action.

The elderly: co-trimoxazole should be used with caution in the elderly as it may cause worse side-effects than in younger patients.

Pregnancy and breastfeeding - please ensure you read the detailed information below


Co-trimoxazole is not safe to take if you are, or are planning to become, pregnant.

It is sensible to limit use of medication during pregnancy whenever possible. However, your doctor may decide that the benefits outweigh the risks in individual circumstances and after a careful assessment of your specific health situation.

If you have any doubts or concerns you are advised to discuss the medicine with your doctor or pharmacist.


Co-trimoxazole is not safe to take if you are breastfeeding.

It is sensible to limit use of medication during breastfeeding whenever possible. However, your doctor may decide that the benefits outweigh the risks in individual circumstances and after a careful assessment of your specific health situation.

If you have any doubts or concerns you are advised to discuss the medicine with your doctor or pharmacist.


Before using this medicine, tell your prescriber of all the medicines you are taking including prescription medicines and medicines you have bought over the counter without a prescription. Tell your prescriber if you are taking vitamins or complementary remedies such as herbal products, as these can also interact with medicines.

If you are taking more than one medicine, these may interact with each other. Your prescriber may decide to use medicines which interact with each other if the benefit outweighs the risks. In these cases, the dose of your medicines may need to be adjusted or you may be monitored more closely.

The following medicines may interact with co-trimoxazole:

  • Medicines used to control abnormal heart rhythms such amiodarone, digoxin or procainamide
  • Other antibiotics such as rifampicin
  • Immunosuppressants such as ciclosporin
  • Blood-thinning drugs such as warfarin
  • Anti-epileptics such as phenytoin
  • Antidiabetics such as glibenclamide, glipizide or tolbutamide
  • Anti-cancer drugs such as methotrexate, azathioprine or mercaptopurine
  • Antimalarials such as pyrimethamine
  • Anti-psychotics such as clozapine
  • Antivirals such as maraviroc, ritonavir, tipranavir or zidovudine

This information does not contain all possible interactions. Therefore, tell your prescriber of all the products you are using before taking this medicine.

If you have a question or want to discuss anything about your medicine, speak to your local pharmacist.


Taking too much co-trimoxazole may cause the following: feeling sick (nausea), vomiting, dizziness and confusion.

People who have taken too much co-trimoxazole should be encouraged to vomit (if this has not already happened) and to seek assistance from a healthcare professional immediately.

If you think you, or someone you care for, might have accidentally taken more than the recommended dose of co-trimoxazole or intentional overdose is suspected, contact your local hospital, GP or if in England call 111. In Scotland call NHS 24. In Wales, call NHS Direct Wales. In the case of medical emergencies, always dial 999.


If you miss a dose, take it as soon as you remember. If it is near the time of the next dose, skip the missed dose and resume your usual dosing schedule. Do not double the dose to catch up.

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CONDITIONS OF USE: The information in this database is intended to supplement, not substitute for, the expertise and judgement of healthcare professionals. The information is not intended to cover all possible uses, directions, precautions, drug interactions or adverse events, nor should it be construed to indicate that use of a particular medicine is safe, appropriate or effective for you or anyone else. A healthcare professional should be consulted before taking any medicine, changing any diet, or discontinuing any course of treatment.

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