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Trimethoprim is an antibiotic which is commonly used to treat urinary tract infections (UTIs) such as Cystitis in women.

Following a quick medical questionnaire, our doctors will determine the medicine is right for you. If approved, our UK dispensing pharmacy will dispense and dispatch your order via a discreet, next-day delivery service.

6 Tablets
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About Product
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What is Trimethoprim?

Trimethoprim is an antibiotic treatment for cystitis - a urinary tract infection (UTI). It is available in tablet form as well as a liquid oral suspension.

It is sometimes prescribed long term for people who have recurrent cystitis as a preventive treatment.

What is Cystitis and how is it caused?

Cystitis is a bacterial infection of the urinary tract. Women are at a greater risk than men of developing urinary tract infections due to the shorter distance between the urethra and anus, and the length of the urethra itself.

While the condition is not classed as a sexually transmitted infection (STI), it is not uncommon for the condition to develop after sexual intercourse. To prevent Cystitis from developing after having sex, you should go to the toilet as soon as you can after sex to flush out the bacteria which may be in your urethra.

The condition can also develop when there is an obstruction in the urinary tract. Such obstructions include bladder and kidney stones, pressure upon the bladder during pregnancy, and presence of foreign bodies such as catheters.

If the bladder cannot empty fully, pools or urine can remain in bladder, providing the perfect conditions for a bacterial infection to develop.

Some underlying health conditions, such as diabetes and multiple sclerosis, can increase the risk of developing a UTI.

Cystitis can also affect men, though this is uncommon. Men who suspect they have a urinary tract infection should arrange an appointment to see their GP, to rule out the cause of their symptoms.

How does Trimethoprim work?

Trimethoprim is antibiotic which prevents bacteria from multiplying.

It does this by inhibiting the bacteria's ability to produce a vitamin called folate, which is needed in order for cells to grow and reproduce. As a result, the bacteria diminish in numbers as they either die or are eradicated by the immune system.

Like other antibiotic treatments, it is important to complete your course of antibiotics, even if your symptoms clear. Failure to finish the antibiotic treatment as prescribed can increase your risk of the infection coming back.

Sometimes, your doctor may require a urine or sputum sample to determine whether the bacterium is resistant to Trimethoprim or not.

How do I take Trimethoprim?

For the treatment of Cystitis, take 200mg of Trimethoprim twice daily for between 3 and 14 days. Your doctor may double your dosage for your initial administration.

Trimethoprim tablets should be swallowed whole with a glass of waters.

Always take your medicine as prescribed by the doctor.

Trimethoprim side effects and cautions

All medicines have the potential of causing side effects, though not everybody gets them. Understand the risks associated with your treatment and being vigilant of side effects is important to your care.

Side effects of Trimethoprim include:

  • Changes in liver enzymes
  • Headache
  • Increase in blood creatinine and urea
  • Increased bruising
  • Irregular heartbeat
  • Itching
  • Jaundice (yellowing of skin and whites of eyes)
  • Muscle cramps and pains
  • Nausea
  • Nose bleeds
  • Sensitivity to light
  • Skin rashes
  • Sore throat
  • Swollen tongue
  • Vomiting

If you experience any side effects, whether listed above or in the patient information leaflet, inform your doctor or consult a pharmacist. You can find your nearest pharmacy using the NHS' Find A Pharmacy service.

Who should not take Trimethoprim?

Trimethoprim might not be suitable for you. During your consultation, please inform our doctors if any of the following applies to you:

  • Are pregnant, intend on becoming pregnant or are breastfeeding
  • Have porphyria
  • Have problems with your blood such as anaemia, low white blood cells or folic acid deficiency
  • Have problems with your kidneys
  • Have problems with your liver

Allergic reaction

If you experience the signs and symptoms of an allergic reaction, stop taking the medicine and speak to your doctor as soon as possible. Seek emergency medical attention if necessary.

Signs of an allergic reaction include:

  • Difficulty breathing
  • Hives
  • Skin rash
  • Swelling of the face, lips, tongue and throat

Interactions with other medicine

Please inform your doctor if you are taking or have recently taken other medicines, including those on prescription, acquired over-the-counter or herbal health supplements. It is especially important to inform our doctors if you are taking any of the following:

  • Antibiotics such as rifampicin
  • Anticoagulants (Warfarin)
  • Bone marrow depressants
  • Ciclosporin (To prevent transplant rejection)
  • Digoxin (To treat heart conditions)
  • Phenytoin (To treat epilepsy)
  • Pyrimethamine (To treat malaria)

This treatment contains lactose - please contact your doctor before using this medicine if you are known to have lactose intolerance.

Driving and operating machinery

Trimethoprim should not affect your ability to drive or operate machinery.

Pregnancy and breastfeeding

If you are pregnant, speak to your doctor before taking Trimethoprim.

Trimethoprim passes into breast milk, though it is not considered to be harmful to your baby. If you are worried about taking Trimethoprim while breastfeeding, speak to your doctor or pharmacist.

Frequently asked questions about Trimethoprim

What should I do if I forget a dose?

If you forget to take a dose of Trimethoprim, take the missed dose as soon as you remember and continue to take your medicine as normal.

Do not take a double dose to make up for the missed dose.

What should I do if I accidentally take too much Trimethoprim?

If you accidentally take too much Trimethoprim, contact your doctor or nearest hospital casualty department.

What should I do if I become pregnant while taking Trimethoprim?

If you become pregnant while taking Trimethoprim, cease taking the treatment and contact your doctor as soon as possible.

Can I still drink alcohol while taking Trimethoprim?

It is considered safe to drink within moderation while taking Trimethoprim. Alcohol does not affect the efficacy of the medicine.

However, alcohol consumption can increase the risk of side effects, or make side effects, such as dizziness, headache or stomach ache, worsen. Therefore, you should limit or avoid alcohol consumption while taking Trimethoprim.

Table of contents

What is Trimethoprim?

How does trimethoprim work?

How to take Trimethoprim?

Side effects and cautions

Frequently asked questions

Additional resources

Why do I keep getting cystitis?

How to prevent Cystitis?

Treatment information

  • Product Name: Trimethoprim
  • Manufacturer: Milpharm
  • Active Ingredient(s): Trimethoprim
  • Administration: Oral
  • Presentation: Tablets
  • Available Strength: 200mg
  • Exemption: Prescription Only
  • Application: Women over 18+
  • Dosage: Take 200mg of Trimethoprim twice daily for between 3 to 14 days
  • Description: Trimethoprim is an antibiotic which is used to treat cystitis
  • Drug Class: Antibiotics
  • Alcohol Consumption: Avoid or limit alcohol consumption
  • When Pregnant: Do not take Trimethoprim if you are pregnant. Speak to your doctor for further advice.
  • When Breastfeeding: Do not take Trimethoprim if you are breastfeeding. Speak to your doctor for further advice.
Click here to view the Trimethoprim - Patient Information Leaflet

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