Trimethoprim

Antibiotic
PRESCRIPTION ONLY IN INDIA

Trimethoprim is a antibiotic found in 1 medicine sold in India, such as Septran DS. Below: what it is for, how it works, how to take it, side effects, interactions and pregnancy advice.

What it is used for

Treats urine infections, alone or with sulfamethoxazole.

How it works

An antibiotic for urinary infections, used alone or with sulfamethoxazole.

How to take it

Usually 200 mg twice a day for 3 to 7 days.

Common side effects

  • Nausea
  • Itching
  • Rash

Get medical help straight away if

  • Sore throat, fever, bruising
  • Severe rash

Be careful

Can raise potassium; not in early pregnancy.

Other medicines and interactions

Raises potassium with ACE inhibitors, ARBs and spironolactone. Raises methotrexate toxicity.

Pregnancy and breastfeeding

Avoid in the first three months of pregnancy (it blocks folate). Acceptable while breastfeeding for short courses.

Combination medicines that contain Trimethoprim (1)

Septran DS

Common questions

What is Trimethoprim used for?

Treats urine infections, alone or with sulfamethoxazole.

How does Trimethoprim work?

An antibiotic for urinary infections, used alone or with sulfamethoxazole.

How should I take Trimethoprim?

Usually 200 mg twice a day for 3 to 7 days.

What are the side effects of Trimethoprim?

Common: Nausea, itching, rash. Get help straight away for: Sore throat, fever, bruising, severe rash.

Does Trimethoprim interact with other medicines?

Raises potassium with ACE inhibitors, ARBs and spironolactone. Raises methotrexate toxicity.

Is Trimethoprim safe in pregnancy and breastfeeding?

Avoid in the first three months of pregnancy (it blocks folate). Acceptable while breastfeeding for short courses.

Does Trimethoprim need a prescription in India?

Yes. In India it is a prescription (Schedule H) medicine, so a pharmacist should sell it only with a doctor's prescription.

Which brands contain Trimethoprim?

Septran DS.

Sources and further reading

NHS (UK National Health Service) and MedlinePlus (US National Library of Medicine) are free, reviewed medicine guides. Brand names and doses there may differ from India.

Last reviewed 31 October 2026. Written by Satya Babu from standard prescribing information.

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For information only, not medical advice. This page is a plain-language summary written from standard prescribing information and the public guides linked below. Brands sometimes change their formula, so always check the composition printed on the pack. Doses here are typical adult doses; yours may differ. Do not start, stop or change a medicine without your doctor or pharmacist, and keep all medicines away from children. In an emergency, call 112 (India) or your local emergency number.