Trimethoprim

  • Trimethoprim is an antibiotic used for treating or preventing chest or urinary tract infections.
  • Take trimethoprim at the same times each day to keep a steady level of trimethoprim in your body.
  • It is important to complete the course prescribed, even if your condition has improved.
  • Side-effects of short courses of treatment with trimethoprim are usually mild.

About trimethoprim

Type of medicineAntibiotic
Used forBacterial infections of the chest or urinary tract
Also calledMonotrim®
Available asTablets and oral suspension

Trimethoprim works by killing or stopping the growth of the bacteria responsible for the infection.

Before taking trimethoprim

Before taking trimethoprim make sure your doctor or pharmacist knows:

  • If you are pregnant, trying for a baby or breast-feeding.
  • If you have kidney problems.
  • If you have porphyria or any other blood disorder.
  • 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 any other medicine.

How to take trimethoprim

  • Before beginning treatment, read the manufacturer's printed information leaflet.
  • Take trimethoprim exactly as directed by your doctor.
  • Try to take trimethoprim at the same times each day to keep a steady level of trimethoprim 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 (at night) to prevent infections.
  • If you forget to take a dose, take one as soon as you remember but do not take two doses at the same time.

Getting the most from your treatment

  • Even if your condition has improved, it is important to complete the course of trimethoprim that you have been given. If you stop taking this medicine too soon your infection may come back and could be more difficult to treat.
  • If you are having any treatment like 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 trimethoprim cause problems?

Along with their useful effects all medicines can cause unwanted side-effects. These usually improve as your body adjusts to the new medicine. 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 medicineWhat can I do if I experience this
Feeling or being sickEat little and often. Stick to simple foods
Mild, itchy skin rashAvoid scrubbing your skin and try applying a gentle, fragrance-free skin moisturiser
Increased skin sensitivity to sunlightAvoid sunbeds. Use a sunscreen (factor 15 or higher) in bright sunlight until you know how your skin reacts

Important: if you develop 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 trimethoprim

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

Important information about all medicines


  • Never take more than the prescribed dose. If you suspect that you or someone else has taken an overdose of this medicine, go to the accident and emergency department of your local hospital at once. Take the container with you, even if it is empty.
  • This medicine is for you. Never give it to other people even if their condition appears to be the same as yours.
  • Never keep out-of-date or unwanted medicines. Take them to your local pharmacy which will dispose of them for you.
  • If you have any questions about this medicine ask your pharmacist.

References

  • Manufacturer's PIL, Trimethoprim Tablets, Actavis UK Ltd, electronic Medicines Compendium. Dated March 2008, accessed December 2009.
  • British National Formulary; 58th Edition (September 2009) British Medical Association and Royal Pharmaceutical Society of Great Britain, London (link to current BNF).
Comprehensive patient resources are available at www.patient.co.uk
© EMIS 2010DocID: 3344DocRef: dils2329Last Reviewed: 5 Jan 2010Version: 22
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