Sulfamethoxazole

Antibiotic (sulfonamide)
PRESCRIPTION ONLY IN INDIA

Sulfamethoxazole is a antibiotic (sulfonamide) 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

Combined with trimethoprim (co-trimoxazole) to treat urine, chest and some other infections.

How it works

A sulfonamide antibiotic, combined with trimethoprim (co-trimoxazole), for urinary infections, some pneumonias and prevention of infections in HIV.

How to take it

Usually twice a day with a full glass of water; drink plenty of fluids.

Common side effects

  • Nausea
  • Rash
  • Loss of appetite
  • Sun sensitivity

Get medical help straight away if

  • Severe rash with blisters or mouth sores (stop at once)
  • Sore throat, fever or bruising
  • Yellow skin

Be careful

Avoid if allergic to sulpha drugs; drink plenty of water. Stop if a rash appears.

Other medicines and interactions

Raises warfarin, methotrexate, phenytoin and some diabetes medicine effects. High potassium with ACE inhibitors and spironolactone.

Pregnancy and breastfeeding

Usually avoided in the first and last three months of pregnancy; ask about breastfeeding.

Combination medicines that contain Sulfamethoxazole (1)

Septran DS

Common questions

What is Sulfamethoxazole used for?

Combined with trimethoprim (co-trimoxazole) to treat urine, chest and some other infections.

How does Sulfamethoxazole work?

A sulfonamide antibiotic, combined with trimethoprim (co-trimoxazole), for urinary infections, some pneumonias and prevention of infections in HIV.

How should I take Sulfamethoxazole?

Usually twice a day with a full glass of water; drink plenty of fluids.

What are the side effects of Sulfamethoxazole?

Common: Nausea, rash, loss of appetite, sun sensitivity. Get help straight away for: Severe rash with blisters or mouth sores (stop at once), sore throat, fever or bruising, yellow skin.

Does Sulfamethoxazole interact with other medicines?

Raises warfarin, methotrexate, phenytoin and some diabetes medicine effects. High potassium with ACE inhibitors and spironolactone.

Is Sulfamethoxazole safe in pregnancy and breastfeeding?

Usually avoided in the first and last three months of pregnancy; ask about breastfeeding.

Does Sulfamethoxazole 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 Sulfamethoxazole?

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.