Trimethoprim
Trimethoprim is an antibiotic used for urinary tract infections and occasionally other infections per local guidelines. Single-dose regimens exist for some uncomplicated UTIs — follow your prescription exactly.
This medicine is part of the Antibiotics (selected) category.
Generic name: trimethoprim
Quick answers
Short replies to searches people often run before speaking to a clinician. For the overview of what the medicine is used for, see the short summary under the page title above.
What is it for?
Trimethoprim is an antibiotic used for urinary tract infections and occasionally other infections per local guidelines.
How long does it take to work?
Onset varies by condition and dose. Your GP or pharmacist can explain what to expect and when to review.
What are common side effects?
Nausea, rash, or itch.
Can you take paracetamol or ibuprofen with it?
Ask your GP or pharmacist before taking Trimethoprim with paracetamol or ibuprofen. Many adults use paracetamol for short periods when appropriate; NSAIDs such as ibuprofen need extra checks with your other medicines and health conditions.
More about what Trimethoprim is used for
Trimethoprim is an antibiotic used for urinary tract infections and occasionally other infections per local guidelines.
Single-dose regimens exist for some uncomplicated UTIs — follow your prescription exactly.
How does Trimethoprim work, and how long does it take to work?
It blocks bacterial folate production, stopping bacterial growth.
Resistance varies — culture results may change treatment.
How and when should you take Trimethoprim?
With or without food as your leaflet states. Drink fluids unless fluid-restricted.
Finish the course unless side effects force review.
What are the common side effects of Trimethoprim?
Nausea, rash, or itch.
Serious side effects of Trimethoprim — when to get urgent help
Seek urgent help for widespread rash with fever, mouth ulcers, or severe allergic reaction.
What if you miss a dose of Trimethoprim?
Take when remembered; space remaining doses evenly; do not double.
Who should not take Trimethoprim?
Severe blood disorders, significant kidney impairment without dose change, and pregnancy in first trimester need prescriber judgement.
Can you take paracetamol or ibuprofen with Trimethoprim? — other interactions
Methotrexate, Warfarin, ACE inhibitors, ARBs, and spironolactone raise hyperkalaemia risk — pharmacist checks are important.
Trimethoprim in pregnancy and breastfeeding
Folate antagonism matters in early pregnancy — discuss urgently if pregnancy is possible.
Blood tests and monitoring on Trimethoprim
Potassium may be checked if you take interacting heart or blood pressure medicines.
What might your GP prescribe instead of Trimethoprim?
Nitrofurantoin, fosfomycin, or Amoxicillin may be alternatives depending on sensitivities.
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Frequently asked questions about Trimethoprim
People also ask — common Google searches
- What is Trimethoprim used for?
- Trimethoprim is an antibiotic used for urinary tract infections and occasionally other infections per local guidelines. Single-dose regimens exist for some uncomplicated UTIs — follow your prescription exactly.
- How long does Trimethoprim take to work?
- Onset varies by condition and dose. Your GP or pharmacist can explain what to expect and when to review. Always follow your prescriber’s follow-up plan.
- Can you take Trimethoprim with paracetamol or ibuprofen?
- Ask your GP or pharmacist before taking Trimethoprim with Paracetamol or Ibuprofen. Many adults use paracetamol for short periods when appropriate; NSAIDs such as ibuprofen need extra checks with your other medicines and health conditions.
- What are the side effects of Trimethoprim?
- Nausea, rash, or itch. See the sections below for more detail, including serious side effects and when to seek urgent help.
- Can trimethoprim raise potassium?
- Yes, especially with ACE inhibitors, ARBs, or spironolactone — your prescriber may arrange a blood test.
- Is trimethoprim a penicillin?
- No — it is a different antibiotic class, sometimes used in penicillin allergy, though allergies can still occur to trimethoprim itself.
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