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Co-trimoxazole

About your medicine

Co-trimoxazole is an antibiotic that you will need to take after your kidney transplant or when you are taking cyclophosphamide or rituximab. It is a combination of 2 medicines called sulfamethoxazole and trimethoprim. It is given at a low dose to prevent you from catching a specific chest infection. You are more likely to get infections while you are taking a lot of immuno-suppressant medicines for your new kidney. When you are asked to take less immuno-suppressant drugs you will be able to stop taking the co-trimoxazole, normally six months after your transplant or finishing cyclophosphamide or rituximab treatment.

Taking your medicine

Before taking your medicine read the information leaflet inside the pack. It will give you more information about the medicine including a full list of the side effects.

You should swallow the tablets whole with a glass of water. The tablets are usually taken once a day. If you have problems swallowing, a liquid is also available.

Unwanted effects

As with all medicines, co-trimoxazole can cause side effects in some people. The most common side effects include feeling sick, being sick and skin rashes. If the tablets make you feel sick try taking them with food. If you develop a rash, you should report it to your doctor straightaway. Rarely side effects include changes that will be noticed with your blood tests, for example changes to your red and white blood cells. This means you may become anaemic, bruise or bleed more easily than usual. Your liver might also be affected, which could cause you to become jaundiced (yellow).

Unwanted effects often improve after a short while however if they are prolonged or troublesome speak with your doctor or pharmacist.

Storing your medicine

You should store the tablets in their original container in a cool, dry place out of the reach of children.

Do not throw out any expired or unwanted medicine by flushing them down the toilet or throwing them away. Take them to your local pharmacy which will dispose of them for you.

Other advice

Always take your tablets as directed by your doctor and only stop them on the advice of your doctor.

Some drugs may cause a problem when taken with co-trimoxazole. For instance, co-trimoxazole should never be taken with methotrexate. Always check with your doctor or pharmacist before taking any other medication along with co-trimoxazole including medicines that you can buy without a prescription or any herbal and complimentary medicines.


The National Kidney Federation cannot accept responsibility for information provided. The above is for guidance only. Patients are advised to seek further information from their own doctor.

NKF Controlled Document No. 66: Co-trimoxazole written: 22/04/2000 last reviewed: 01/10/2016