Pharmacy - LUHFT wide

What you need to know about monitoring for side effects

 

What is co-trimoxazole and what is it used for?

Co-trimoxazole is an antibiotic that is used to treat infections caused by certain bacteria. It is a combination of two different antibiotics called trimethoprim and sulfamethoxazole.

Co-trimoxazole can be used to treat infections including:

  • Infections caused by bacteria.
  • A type of pneumonia known as Pneumocystis jirovecii (PJP) (formally known as PCP or Pneumocystis carinii). This is a fungus that can infect the lungs.

Co-trimoxazole can also be used to help prevent infections. This is known as prophylactic use.

You may be offered prophylactic co-trimoxazole to help prevent pneumonia caused by PJP, if your immune system has become weakened for any reason or if you are taking medications that can stop your immune system from working as well.

Do I need to know anything before I take co-trimoxazole?

Do not take co-trimoxazole if:

  • You are allergic to sulfamethoxazole, trimethoprim or co-trimoxazole.
  • You have been diagnosed with a rare blood problem called porphyria which can affect the skin and nervous system.
  • You are in the first trimester of pregnancy.

If you have any of the following medical conditions, only take co-trimoxazole if your doctor has specifically advise:

  • You have a history of problems with your blood causing bleeding or bruising (thrombocytopenia/low platelet count).
  • You have severe liver or kidney problems.
  • If you have a G6PD deficiency or predisposition to folate deficiency.

You should not take methotrexate and co-trimoxazole together as it can be dangerous. Methotrexate is a drug prescribed by specialist doctors to treat certain cancers and autoimmune conditions (such as rheumatoid arthritis and severe psoriasis).                      

How do I take co-trimoxazole?

The dose prescribed will vary depending on the reason you have been prescribed co-trimoxazole. It is usually taken twice a day (12 hours apart, for example 8am and 8pm).

Different doses are used to prevent infections (prophylactic use) and to treat bacterial/PJP infections. Your doctor or pharmacist will advise you how much co-trimoxazole to take. Always take this medicine exactly as your doctor has told you.

Co-trimoxazole can cause an upset stomach. You may wish to take co-trimoxazole with food to reduce the chance of this happening.

It is important that you remain well hydrated whilst taking co-trimoxazole, try to drink approximately eight glasses of water per day.

What should I do if I miss a dose?

Try not to miss a dose of co-trimoxazole as this can lead to bacterial resistance and treatment failure. However, if you do miss a dose, do not double up when the next dose is due. Take the next dose as soon as you remember and continue taking your tablets every 12 hours.

How long will I need to take co-trimoxazole for?

This depends on what infection you are being treated for, your blood results and how well you respond to treatment. Co-trimoxazole should be taken until the course is complete as determined by your doctor. Do not stop taking the medication when you start to feel better, as stopping too soon may lead to surviving bacteria causing a relapse in the infection.

If you are taking prophylactic co-trimoxazole, this will likely be long term and your doctor will explain when or if this can be stopped depending on what other medications you are taking and how your immune system is working. 

Will I require any monitoring?

If you are taking co-trimoxazole for a prolonged period, you will need to have regular blood tests. These blood tests are done to check that your kidneys and liver are working well. They will also check the levels of different cells in your blood to make sure your red blood cell level is not too low and that you are not at an increased risk of infection.

Your doctor will advise you how frequently you will need monitoring, this will be less frequent if you are on a prophylactic dose.

Additional blood tests may be requested at any time in between scheduled dates if new problems develop.

What side effects might I experience on co-trimoxazole?

Like all medications, co-trimoxazole can cause side effects however these will not affect everyone.

Common side effects include:

  • Thrush
  • Nausea
  • Diarrhoea
  • Rash

Co-trimoxazole can make your skin more sensitive to light. You should wear sun cream and avoid sunbathing whilst taking these antibiotics.

In rare cases, more serious side effects can occur; these are more likely in prolonged treatment courses. If you notice any of the following symptoms, stop treatment with co-trimoxazole and contact the hospital team immediately.

Chances of an allergic reaction are rare, common symptoms include:

  • Difficulty breathing/shortness of breath.
  • Swelling of face, mouth, tongue and throat which may cause difficulty in swallowing.
  • Chest pain.
  • Red rash on skin.
  • Fainting.

Bruising or easy bleeding

Sometimes co-trimoxazole can affect the bone marrow and stop it working effectively so your blood cannot clot properly and you cannot fight infection. You might notice:

  • A sore throat.
  • Easy bruising or bleeding.
  • A fever.
  • Feeling very tired.

If you notice any of these symptoms, you will need urgent blood tests and review in hospital.

High potassium levels

Potassium is a salt in the blood and high levels of this can cause problems such as:

  • Palpitations (feeling like your heart is beating irregularly).
  • Chest pain.
  • Tingling in your hands or feet.

There are lots of other causes for these symptoms but if they happen whilst taking co-trimoxazole, you will need urgent blood tests to review your kidney function and make sure your potassium levels are safe.

Can I take my current medication with co-trimoxazole?

It is important that you tell your doctor if you are taking any other medicines, including over the counter medicines, vitamins or herbal remedies. Your doctor or pharmacist can advise whether it is safe for you to take co-trimoxazole with any other medications you are on which may interact.

Where will I get further supplies of co-trimoxazole?

If you need further supplies, then this will be prescribed by your hospital doctor and dispensed by the hospital pharmacy. If you have not had required blood tests, this may delay receiving further supplies.

Prophylactic doses will be prescribed by your hospital doctor, in some circumstances your GP may continue to prescribe after discussion with your hospital doctor.

Can I take co-trimoxazole during pregnancy or breastfeeding?

You should not take co-trimoxazole if you are pregnant.

Co-trimoxazole is generally safe to use if you are breastfeeding. However there are some situations where it may not be safe to use, for example if your baby is jaundices (yellowing of your baby’s skin or eyes).

Who can I tell about my side effects?

If you have any questions about linezolid please contact your pharmacist, doctor or nurse. Please report any side effects to the MHRA via the Yellow Card Scheme. Reports are confidential and help to improve the safety of medicines (https://yellowcard.mhra.gov/uk/).

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Further information

Pharmacy Departments

 

Royal Liverpool Hospital

Tel: 0151 706 2092

 

Aintree Hospital Tel: 0151 525 5980

 

Broadgreen Hospital Tel: 0151 282 6056

 

Author: Pharmacy

Review date: April 2029

PI 3250 V1