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Taking trimethoprim with other medicines and herbal supplements

Cautions with other medicines

Some medicines affect the way trimethoprim works and increase the chances of you having side effects.

Check with a pharmacist or your doctor if you're taking any other medicines, including:

  • rifampicin, an antibiotic
  • warfarin or acenocoumarol (Sinthrome), medicines to treat or help prevent blood clots (anticoagulants)
  • digoxin, a heart medicine
  • phenytoin, an epilepsy medicine
  • replaglinide or pioglitazone, diabetes medicines
  • methotrexate, an immune system medicine, also used to treat some types of cancer

These are not all the medicines that may cause problems if you take them with trimethoprim. For a full list, see the leaflet inside your medicine packet.

Important

Tell your doctor if you've recently had, or are due to have, an oral typhoid vaccine. Trimethoprim can make it less effective.

Mixing trimethoprim with herbal remedies and supplements

There's not enough information to say that complementary medicines, herbal remedies or supplements are safe to take with trimethoprim. They're not tested in the same way as pharmacy and prescription medicines. They're generally not tested for the effect they have on other medicines

Important: Medicine safety

Tell your doctor or pharmacist if you're taking any other medicines, including herbal remedies, vitamins or supplements.

Page last reviewed: 26 November 2025
Next review due: 26 November 2028