Patient leaflet - Trimethoprim 100 mg tablets

1. What Trimethoprim tablets are and what they are used for

Trimethoprim is a type of antibacterial medicine which works by killing bacteria. Trimethoprim tablets may be used:

to treat a wide range of infections including urinary infections and respiratory tract infections. • for long-term prevention of recurrent urinary tract infections.

2. What you need to know before you take Trimethoprim Tablets

Do not take Trimethoprim Tablets if you

are allergic (hypersensitive) to trimethoprim or any of the other ingredients of this medicine (listed in section 6)
are pregnant (ﬁrst 3 months) or might be pregnant
suﬀer from any blood disorders such as anaemia.
suﬀer from severe liver problems
have ever developed a severe skin rash or skin peeling, blistering and/or mouth sores after taking
trimethoprim.
Trimethoprim should not be administered to premature babies or infants under 4 months of age. The tablet form is NOT recommended for use in children under 6 years - the oral liquid form should be used.
Warnings and Precautions
Talk to your doctor or pharmacist before taking Trimethoprim tablets if you:
- are pregnant
- suﬀer from kidney problems/kidney disease or are having dialysis treatment. • have a deﬁciency (are low) in folic acid (may cause anaemia)
- are at greater risk of high levels of potassium in your blood (hyperkalaemia), e.g. the elderly or
  those on higher doses
- are also taking repaglinide (medicine for treating diabetes)
- suﬀer from porphyria (a disorder that causes skin sensitivity to light, pain attacks and muscle
  weakness)
- Trimethoprim should not be given to premature babies or babies during the ﬁrst few weeks of • life.

You should let your doctor know and ask his/her advice if you suﬀer from or have ever had any of the above.

Trimethoprim can increase potassium blood levels. Patients at risk of increased potassium blood levels include those with kidney problems, poorly controlled diabetes, or those on certain medicines or potassium supplements. The symptoms of severe hyperkalaemia might include muscle cramps, irregular heart rhythm, diarrhoea, nausea, dizziness or headache. Your doctor may perform blood tests to monitor your potassium blood levels.

Your doctor may wish to do regular blood tests if you need long-term treatment or are prone to anaemia.

Take special care with Trimethoprim:

Serious skin reactions, such as Stevens-Johnson syndrome (SJS), toxic epidermal necrolysis (TEN), drug reaction with eosinophilia and systemic symptoms (DRESS) have been reported in association with trimethoprim treatment. Stop using trimethoprim and seek medical attention immediately if you notice any of the symptoms related to these serious skin reactions described in section 4.

Other medicines and Trimethoprim Tablets

Tell your doctor or pharmacist if you are taking, have recently taken or might take any other medicines, even those are not prescribed. Your medicine may interfere with other medicines that you are taking.

560 MM

Take care with the following medicines:

3. How to take Trimethoprim Tablets Manufacturer

Trimethoprim Tablets contain lactose

repaglinide, used to treat diabetes
If you have been told by your doctor that you have intolerance to some sugars, contact your doctor before taking this medicinal product.
procainamide, to treat abnormal heart rhythm
digoxin, to treat certain heart conditions
potassium supplements
Information on sodium content
medicines known as ACE inhibitors and angiotensin II antagonists (used to treat high blood pressure and certain heart conditions).
This medicine contains less than 1 mmol sodium (23 mg) per tablet, that is to say essentially ‘sodium free’.
heparin (used to treat and prevent blood clots)
diuretics (water tablets such as furosemide, eplerenone, spironolactone, amiloride or triamterene) • rifampicin (antibiotic), used to treat TB
anticoagulants (to prevent clots from forming in the blood e.g. warfarin)
- Always take this medicine exactly as your doctor or pharmacist has told you. Check with your doctor or pharmacist if you are not sure.
phenytoin, to treat epilepsy
pyrimethamine and dapsone, used to treat malaria
- Trimethoprim tablets are for oral administration only and should be swallowed with a drink of water. Do not crush or chew this tablets.
immunosuppressant drugs - used in cancer treatment (e.g. methotrexate) or to treat organ rejection after transplant (e.g. azathioprine or ciclosporin)
bone marrow depressants
Dosage
spironolactone
Severe or sudden infections:
- Adults and children over 12 years: 200 mg twice daily.

Pregnancy and breast feeding

Children 6 years to 12 years: 100 mg twice daily.

If you are pregnant or breast-feeding, think you may be pregnant or are planning to have a baby, ask your doctor or pharmacist for advice before taking this medicine. Trimethoprim should not be used in pregnancy. DO NOT take Trimethoprim Tablets if you are pregnant.

Long-term treatment and prevention therapy:

Adults and children over 12 years: 100 mg at night.
Children 6-12 years: 50mg at night. Where a single daily dose is required, dosage at bedtime may maximise urinary concentrations.

This medicine should not be taken during ﬁrst three months of pregnancy. Treatment with trimethoprim in the ﬁrst three months of pregnancy may increase the risk of miscarriage.

The usual dose is around 2mg/kg body weight of the child per day.

Children born to mothers treated with trimethoprim during the ﬁrst trimester of pregnancy may have an increased risk of birth defects, in particular neural tube defects (where the spine and spinal cord do not form properly), oral clefts (where the lip and palate do not form properly) and defects aﬀecting the heart.

Children: Trimethoprim tablets are not recommended for children under 6 years of age. Your doctor has carefully chosen the correct dosage for you, taking into account the severity of your condition, your age and any other particular reasons special to you. Instructions on how many tablets to take and when to take them will be printed on the dispensing label on the pack.

Trimethoprim is excreted in breast milk. If you are breast-feeding, ask your doctor or pharmacist for advice before taking this medicine

Driving and using machines

There is no evidence to suggest that Trimethoprim Tablets aﬀect the ability to drive or operate machinery.

Never change the dose of your medicine without talking to your doctor ﬁrst.

Elderly: doses may be reduced in elderly patients. Your doctor will prescribe a suitable dose depending on how well your kidneys are working.

If you take more of your medicine than you should

If you (your child or someone else) take too many tablets, tell a doctor or pharmacist or go to the nearest hospital casualty department straight away. Remember to take this leaﬂet and the tablet packaging with you.

If you forget to take Trimethoprim tablets

If you forget to take a dose, take it as soon as you remember it and then take the next dose at the right time. Do not take a double dose to make up for a forgotten dose.

If you stop taking your medicine

Keep taking this medicine until your doctor tells you to stop. Do not stop taking it just because you feel better. If you stop taking this medicine, your condition may re-occur or get worse. If you experience symptoms on stopping treatment, contact your doctor. If you have any further questions on the use of this medicine, ask your doctor or pharmacist.

4. Possible Side Eﬀects

Like all medicines, this medicine can cause side eﬀects, although not everybody gets them. Rare serious allergic reactions have occurred known as anaphylactic or anaphylactoid reactions.

Stop taking Trimethoprim and contact your doctor or go to a hospital straightaway if you experience any of the following:

Allergic reactions such as swelling of the face, lips, tongue or throat, diﬃculty breathing, shock, fainting or collapse, skin eruptions/lesions, deep swelling of the skin (angioedema) • Reddish patches on the trunk, often with central blisters, skin peeling, ulcers of mouth, throat, nose, genitals and eyes. These serious skin rashes can be preceded by fever and ﬂu-like symptoms (Stevens Johnson syndrome (SJS)/ Toxic Epidermal Necrolysis (TEN)).
Widespread rash, high body temperature and enlarged lymph nodes (DRESS syndrome or drug hypersensitivity syndrome)
Pancreatitis (signs may include a sudden, severe upper abdominal pain)
Jaundice (yellowing of the skin or whites of the eyes)
Elevation of serum transaminases (an indication of liver damage)
Elevation of bilirubin levels
Chest pain

Tell your doctor or pharmacist if you notice any of the following side eﬀects: Very Common (may aﬀect more than 1 in 10 people)

hyperkalaemia (particularly in the elderly and in HIV patients) which is high levels of potassium in the blood (may result in abnormal heart rhythm)

Common (may aﬀect up to 1 in 10 people)

feeling and being sick, diarrhoea, nausea, vomiting
skin rashes, thrush
hives, headaches

Trimethoprim Tablets INSERT

560 x 160 mm

Front

To request a copy of this leaﬂet in Braille, large print or audio format, please contact the marketing authorisation holder at the address (telephone or email) above. Very rare (may aﬀect up to 1 in 10,000 people)

Reporting of side eﬀects

constipation, severe watery/bloody diarrhoea
If you get any side eﬀects, talk to your doctor, pharmacist or nurse. This includes any possible side eﬀects not listed in this leaﬂet. You can also report side eﬀects directly via the Yellow Card Scheme Website: www.mhra.gov.uk/yellowcard or search for MHRA Yellow Card in the Google Play or Apple App Store. By reporting side eﬀects you can help provide more information on the safety of this medicine.
Bristol Laboratories Ltd.
aseptic meningitis can occur in some patients. This may show as a combination of symptoms such as headache, fever, stiﬀ neck, tiredness, feeling ill and your eyes become very sensitive to bright light • kidney problems (signs may include painful urination or blood in the urine) • pins and needles, shakiness, tremors
Laporte Way, Luton,
Bedfordshire, LU4 8WL,
United Kingdom
increased sensitivity of the skin to the sun
Trimethoprim 100mg Tablets; PL 17907/0092 Trimethoprim 200mg Tablets; PL 17907/0093
low levels of sodium in the blood (may cause nausea, tiredness, muscle cramping) • depression, anxiety, sleeping diﬃculties and nightmares

5. How to Store Trimethoprim Tablets

shortness of breath, wheezing, nosebleeds
- Keep this medicine out of the sight and reach of children.
  This leaﬂet was last revised in May 2026
lupus erythematosus (an auto-immune disorder - an allergic condition which causes joint pain, skin rashes and fever)
- Do not use the tablets after the expiry date shown on the carton or label. The expiry date refers to the last day of that month.
  O
purple discolorations of the skin
- Blisters: Do not store above 25 C.
allergic reaction (hypersensitivity, anaphylaxis), inﬂammation to small vessels (allergic vasculitis), drug allergy (anaphylactoid reaction drug fever)
Store in the original package.
O
- Containers: Do not store above 25 C. Store in the original container.
reduction in numbers of blood cells
Keep the container tightly closed.
anaemia (decrease in red blood cells)
- Do not throw away any medicines via waste water or household waste. Ask your pharmacist how to throw away medicines you no longer use. These measures will help protect the environment.
sore tongue and mouth
sore throat

6. Contents of the pack and other information

confusion, hallucinations
joint and muscle ache
anorexia (loss of appetite or a loss of interest in food)
What Trimethoprim tablets contain
low blood sugar
- The active substance in Trimethoprim tablets is Trimethoprim
eye redness and pain
- The other ingredients in Trimethoprim tablets are Lactose monohydrate, povidone K-25, crospovidone, sodium starch glycolate, magnesium stearate.
convulsions (ﬁts)
cough
agitation
What Trimethoprim tablets look like and contents of the pack.
abnormal behaviour
- Trimethoprim tablets are white to oﬀ-white, circular, ﬂat bevelled edged uncoated tablets with break line dividing ‘TMP’ and ‘100’ or ‘200’ on one side and plain on the other side. • The containers are available in pack sizes of 50, 100, 250 and 500 tablets.
tiredness, dizziness
involuntary movements
ringing in the ears, vertigo (sense that your surroundings are spinning or moving)
- The blister packs are available in sizes of 14, 28, 56, and 84 tablets. Not all pack sizes may be marketed.

Unknown (frequency cannot be estimated)

sore throats or mouth ulcers (due to a decrease in white blood cells)
Marketing Authorisation Holder and Manufacturer
Gastrointestinal disturbances (stomach discomfort)
Name and address:
Pruritus (itching)
Bristol Laboratories Limited,
Elevation of serum creatinine and blood urea nitrogen levels
Unit 3, Canalside, Northbridge Road,
Berkhamsted, Herts, HP4 1EG, UK

If any side eﬀects get serious, or if you notice any side eﬀects not listed in this leaﬂet, please tell your doctor or pharmacist.

Telephone: 0044 (0) 1442 200922

E-mail: info@bristol-labs.co.uk

V19 21-05-26 D0