Trimethoprim Tablets

Price range: £5.49 through £11.99

Trimethoprim tablets are a prescription antibiotic used for the treatment and prevention of urinary tract infections.
A first-line option trusted across UK clinical practice.
Packaging and branding may differ from image shown.

Start Assessment

Description

Trimethoprim is a widely used antibiotic designed to treat bacterial infections, most notably urinary tract infections (UTIs). It works by inhibiting bacterial DNA synthesis, halting the growth of the bacteria responsible for the infection.

It is typically prescribed for short-term use in acute UTIs, particularly in women, but may also be used as a long-term prophylactic treatment for recurrent infections. Trimethoprim is also effective in certain respiratory or gastrointestinal infections when clinically indicated.

Standard formulations include 100mg (for prophylaxis) and 200mg (for active infection). For uncomplicated UTIs, it is commonly prescribed as 200mg twice daily for 3 days. In cases requiring extended coverage or prophylactic use, dosage and duration will be tailored by a GP.

Trimethoprim is well-absorbed and typically begins to relieve symptoms within the first 1–2 days of treatment. It is important to complete the entire prescribed course, even if symptoms resolve early, to prevent resistance and recurrence.

How It Works

Trimethoprim blocks the bacterial enzyme dihydrofolate reductase, essential for DNA replication. This action prevents bacteria from multiplying, allowing the immune system to eliminate the remaining infection.

Why Choose Trimethoprim

Rapid and reliable UTI symptom relief

Targeted action against most common urinary pathogens

Available in short-course or long-term prophylactic dosing

Trusted by GPs and widely used in UK healthcare settings

Important Note

Take Trimethoprim exactly as prescribed. It should be taken with water and can be taken with or without food. Ensure adequate fluid intake during treatment. Do not share with others, even if symptoms appear similar.

Report any rashes, fever, or unusual symptoms to a healthcare provider, particularly if you have a history of sulfa allergies or kidney/liver problems.

Directions

Note: Follow the leaflet and GP instructions carefully.

  • Standard adult dose: 200mg twice daily for 3 to 7 days for acute UTI

  • For prophylaxis: 100mg once daily at night (if prescribed)

  • Swallow tablets with water, with or without food

  • Complete the full course, even if symptoms resolve early

Storage:

  • Store below 25°C

  • Keep in original packaging

  • Keep out of reach of children

Ingredients

  • Active Ingredient:

    • Trimethoprim 100mg or 200mg

  • Other Ingredients May Include:

    • Lactose monohydrate

    • Maize starch

    • Magnesium stearate

Side Effects

Common side effects:

  • Nausea

  • Skin rash

  • Headache

  • Diarrhoea

Rare but serious:

  • Blood disorders (monitor with long-term use)

  • Severe allergic reaction

  • Liver or kidney function changes

Seek immediate advice if rash, jaundice, sore throat, or easy bruising occurs.

Warnings

  • Avoid if allergic to Trimethoprim or sulfonamides

  • Not routinely used during early pregnancy or folate deficiency

  • Use caution in renal or hepatic impairment

  • May interact with methotrexate, warfarin, or diuretics

  • Most people begin to feel better within 24 to 48 hours of starting the treatment. However, you should still complete the full course, even if symptoms improve early.
  • There’s no direct interaction between Trimethoprim and alcohol, but drinking may increase the risk of side effects like nausea. It’s best to avoid alcohol until you finish the course.
  • Take it as soon as you remember. If it’s nearly time for your next dose, skip the missed one — don’t double up. Always aim to take doses at evenly spaced intervals.
  • Yes, doctors may prescribe Trimethoprim for certain chest infections, especially if they’re caused by specific types of bacteria. Always follow medical advice for the best results.
  • Trimethoprim isn’t usually recommended during pregnancy, especially in the first trimester. If you’re pregnant or trying for a baby, speak to your doctor before taking it.