Patient leaflet - Trimethoprim tablets BP 100 mg
1. What Trimethoprim Tablets are and what they are used for
Trimethoprim belongs to a group of medicines known as anti-bacterials which are effective against a wide range of bacteria. Trimethoprim Tablets may be used:
- to treat a wide range of infections including urinary infections and respiratory tract infections.
- for 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 to Trimethoprim or to any of the other ingredients of this medicine (listed in section 6)
- you have severe liver problems
- you have a blood disorders such as anaemia
- you are pregnant (first 3 months) or might be pregnant
This medicine should not be given to premature babies or babies under 4 months old.
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 before taking Trimethoprim Tablets if:
- you are pregnant or think you may be pregnant
- you have porphyria (a disorder that causes skin sensitivity to light, pain attacks and muscle weakness)
- you have kidney problems/disease or are having dialysis treatment
- you have a deficiency (are low) on folic acid (may cause anaemia)
- you are at greater risk of high levels of potassium in your blood (hyperkalaemia), e.g. the elderly or those on higher doses
- you are also taking repaglinide (medicine for treating diabetes)
- have fructose intolerance or an intolerance to some sugars.
- Trimethoprim should not be given to premature babies or babies during the first few weeks of life.
- you have ever developed a severe skin rash or skin peeling, blistering and/or mouth sores after taking trimethoprim. You should let your doctor know and ask his/her advice if you suffer from or have ever had any of the above.
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.
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.
Children
This dosage form is not suitable for use in children younger than 6 years.
Other medicines and Trimethoprim Tablets
Tell your doctor or pharmacist if you are taking, have recently taken or might take any other medicines. Your medicine may interfere with other medicines that you are taking. This is especially important if you are taking:
- Repaglinide, used to treat diabetes
- Procainamide, to treat abnormal heart rhythm
- Pyrimethamine and dapsone, used for the treatment of malaria
- Anticoagulants (to prevent clots from forming in the blood e.g. warfarin)
- Phenytoin (to treat epilepsy)
- Rifampicin (antibiotic), used to treat TB
- Digoxin (used to treat heart conditions)
- Immunosuppressant drugs used to treat some cancers (e.g. methotrexate) or to treat organ rejection after transplant (e.g. azathioprine or ciclosporin)
- Drugs which depress bone marrow
- Diuretics (water tablets such as spironolactone, eplerone, amiloride or triamterene)
- Potassium supplements
- Medicines known as ACE inhibitors and angiotensin II antagonists (used to treat high blood pressure and certain heart conditions).
- Heparin (used to treat and prevent blood clots)
- Bone marrow depressants.
Pregnancy, breast-feeding and fertility
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. 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. 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. 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.
Trimethoprim Tablets contains Lactose:
If you have been told by your doctor that you have an intolerance to some sugars, contact your doctor before taking this medicinal product. Trimethoprim Tablets contains Sodium
This medicine contains less than 1mmol sodium (23mg) per tablet, that is to say essentially ‘sodium-free’.
3. How to take Trimethoprim Tablets
Always take this medicine exactly as your doctor or pharmacist has told you. Check with your doctor or pharmacist if you are not sure. Swallow the tablets with a glass of water, but not chewed at the same time each day.
The recommended doses are:
Adults and children over 12 years:
Severe or sudden infections: usually your doctor will prescribe 200mg taken twice daily.
Long term treatment and prevention therapy: 100mg at night.
Elderly
Dosage is dependent on kidney function.
Elderly patients with kidney problems will usually be prescribed a reduced dose.
Children aged 6 – 12 years
Severe or sudden infections: 100mg twice daily.
Long term treatment and prevention therapy: 50mg at night.
The usual dose is around 2mg/kg body weight of the child per day.
Children under 6
This tablet form of Trimethoprim is not recommended for use in children under 6 years.
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
trimethoprim 100mg & 200mg
Tablets
| Process Black |
P3697T Never change the dose of your medicine without talking to your doctor first.
If you take more Trimethoprim Tablets than you should
Contact your doctor straight away or go to the nearest hospital casualty department. Take with you any remaining tablets and the pack so that the medicine can be identified.
If you forget to take Trimethoprim Tablets
Take it as soon as you remember. However, if it is almost time for your next dose, skip the missed dose and continue with your normal dosing schedule. Do not take a double dose to make up for a forgotten tablet.
If you stop taking Trimethoprim Tablets
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, Trimethoprim Tablets can cause side effects, although not everybody gets them.
Rare serious allergic reactions have occurred known as anaphylactic or anaphylactoid reactions.
STOP TAKING the tablets and contact your doctor or go to your nearest hospital casualty department IMMEDIATELY if you notice any of the following symptoms:
- difficulty breathing, swelling of the face, lips, tongue and throat
- chest pain, shock, fainting or collapse
- deep swelling of the skin (angioedema)
- blistering/peeling of the skin, skin eruptions/lesions
- 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.
- 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) 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)
- nausea, diarrhoea and vomiting
- thrush
- headache
- skin rashes
- hives
Very rare (may affect up to 1 in 10,000 people)
- constipation, severe watery/bloody diarrhoea
- cough
- agitation
- abnormal behaviour
- 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)
- dizziness, tiredness
- convulsions
- involuntary movements
- pins and needles, shakiness, tremors
- ringing in the ears, vertigo
- eye redness and pain
- increased sensitivity of the skin to the sun
- low blood sugar
- low levels of sodium in the blood (may cause nausea, tiredness, muscle cramping)
- anorexia
- depression, anxiety, sleeping difficulties and nightmares
- confusion, hallucinations
- joint and muscle ache
- shortness of breath, wheezing, nosebleeds
- lupus erythematosus (an auto-immune disorder)
- purple discolorations of the skin
- hypersensitivity, anaphylaxis, anaphylactoid reaction drug fever, allergic vasculitis
- reduction in numbers of blood cells
- elevation of serum transaminases, (an indication of liver damage)
- elevation of bilirubin levels
- sore tongue and mouth
- anaemia
- sore throat
- reduction in numbers of blood cells.
Unknown (frequency cannot be estimated from the available data)
- pruritus (itching)
- elevation of serum creatinine and blood urea nitrogen levels.
- gastro-intestinal disorders.
If any side effects get serious, or if you notice any side effects not listed in this leaflet, please tell your doctor or pharmacist. Reporting of side effects
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 at 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.
5. How to store Trimethoprim Tablets
Keep this medicine out of the sight and reach of children.
Do not use this medicine after the expiry date which is stated on the pack, after EXP. The expiry date refers to the last day of that month. Store below 25ºC. Keep in the original package in order to protect from light and moisture.
Do not throw away any medicines via wastewater or household waste. Ask your pharmacist how to throw away medicines you no longer use. These measures will help protect the environment.
6. Contents of the pack and other information
What Trimethoprim Tablets contain:
- The active substance is trimethoprim. Each tablet contains either 100mg or 200mg of trimethoprim.
- Other ingredients are lactose, maize starch, pregelatinised maize starch, magnesium stearate and sodium starch glycolate. What Trimethoprim Tablets look like and contents of the pack:
Trimethoprim Tablets 100mg are white, round, engraved on one side with the company logo and with a break line and A307 on the other side. Trimethoprim Tablets 200mg are white, round, engraved on one side with the company logo and with a break line and A322 on the other side. The score line is only to facilitate breaking for ease of swallowing and not to divide into equal doses.
The medicine is available in pack sizes of 9, 10, 14, 15, 20, 21, 28, 30, 50, 56, 84, 100, 250, 500 and 1000 tablets. Not all pack sizes may be marketed. Marketing Authorisation Holder and Manufacturer
Crescent Pharma Ltd., Key House, Sarum Hill, Basingstoke, RG21 8SR, UK.
This leaflet was last revised: January 2026.
If you would like this leaflet in a different format please contact the licence holder at the above address.