Trimethoprim — Drug Interactions, Alcohol & Pregnancy Guide
Last reviewed: · Source: US FDA drug label database · 247CanITakeWith Editorial Team
- Trimethoprim is a Antibiotic (dihydrofolate reductase inhibitor) used for UTIs.
- Alcohol: Avoid alcohol with trimethoprim — it impairs your immune system while you are fighting a UTI and may worsen nausea.
- Pregnancy: Avoid trimethoprim in the first trimester — it blocks folic acid, which the baby's neural tube needs; nitrofurantoin is the usual UTI alternative.
About Trimethoprim
Trimethoprim is a common antibiotic for uncomplicated UTIs, especially in women. It should be avoided in pregnancy (folate antagonist) and in those with folate deficiency or blood disorders.
Also sold as: Monotrim
Trimethoprim at a glance
Trimethoprim is classed as antibiotic (dihydrofolate reductase inhibitor) and is used for utis, lower respiratory tract infections. It is a prescription medicine, so doses and combinations should always be agreed with your prescriber or pharmacist.
Typical adult dosing guidance: 200mg twice daily for 7 days for UTI. Your own label or prescription always takes priority over general figures.
Interactions most often flagged
- Alcohol
- Pregnancy (avoid)
- Methotrexate
Before you combine Trimethoprim with anything new
- Read the patient information leaflet for both products.
- Keep one up-to-date list of every medicine and supplement you take.
- Ask a pharmacist — it is free and takes a couple of minutes.
- Seek urgent medical help if you feel seriously unwell after combining medicines.
Trimethoprim and Alcohol
Avoid alcohol with trimethoprim — it impairs your immune system while you are fighting a UTI and may worsen nausea.
Full guide →Trimethoprim in Pregnancy
Avoid trimethoprim in the first trimester — it blocks folic acid, which the baby's neural tube needs; nitrofurantoin is the usual UTI alternative.
Full guide →More in this category: antibiotics
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Frequently Asked Questions
What is Trimethoprim used for?
Trimethoprim is a Antibiotic (dihydrofolate reductase inhibitor) used for UTIs, Lower respiratory tract infections.
What is the maximum adult dose of Trimethoprim?
The maximum adult dose is 200mg twice daily for 7 days for UTI. This is general guidance — always follow the dose on your prescription or product label, and check with a pharmacist if you're unsure.
Can I drink alcohol with Trimethoprim?
Avoid alcohol with trimethoprim — it impairs your immune system while you are fighting a UTI and may worsen nausea.
Is Trimethoprim safe to take during pregnancy?
Avoid trimethoprim in the first trimester — it blocks folic acid, which the baby's neural tube needs; nitrofurantoin is the usual UTI alternative.
Is Trimethoprim available over the counter in the UK?
Trimethoprim is prescription-only in the UK.
What should I check before taking Trimethoprim with other medicines?
The interactions most often flagged for Trimethoprim are: alcohol, pregnancy (avoid), methotrexate. Tell your pharmacist or prescriber about everything you take, including over-the-counter products, supplements and herbal remedies, before combining it with anything new.
What are the brand names for Trimethoprim?
Trimethoprim is sold under brand names including Monotrim. The active ingredient is the same, so check labels carefully to avoid doubling up on it.
Do I need a prescription for Trimethoprim?
Trimethoprim is a prescription medicine, so take it exactly as your prescriber directed and ask them before changing the dose.
Not sure if Trimethoprim is safe with your other medications?
HealthLabs.com lets you check liver enzyme or kidney function levels before combining medications long-term — no GP referral needed.
Check your levels at HealthLabs →Always speak to your pharmacist or GP for personalised medical advice. Affiliate link — we may earn a commission.