Trimethoprim (By mouth)


Trimethoprim (trye-METH-oh-prim)

Treats infections, including urinary tract infections and ear infections.

Brand Name(s)


When This Medicine Should Not Be Used

How to Use This Medicine

Liquid, Tablet

  • Take your medicine as directed.
  • Measure the oral liquid medicine with a marked measuring spoon, oral syringe, or medicine cup.
  • You may take your medicine with food to avoid stomach upset.
  • Take all of the medicine in your prescription to clear up your infection, even if you feel better after the first few doses.

If a dose is missed:

  • Take a dose as soon as you remember. If it is almost time for your next dose, wait until then and take a regular dose. Do not take extra medicine to make up for a missed dose.

How to Store and Dispose of This Medicine

  • Store the medicine in a closed container at room temperature, away from heat, moisture, and direct light.
  • Ask your pharmacist, doctor, or health caregiver about the best way to dispose of any outdated medicine or medicine no longer needed.
  • Keep all medicine out of the reach of children. Never share your medicine with anyone.

Drugs and Foods to Avoid

Ask your doctor or pharmacist before using any other medicine, including over-the-counter medicines, vitamins, and herbal products.

  • Make sure your doctor knows if you are using phenytoin (Dilantin®).

Warnings While Using This Medicine

  • Make sure your doctor knows if you are pregnant or breast feeding, or if you have liver or kidney disease.
  • Tell any doctor or dentist who treats you that you are using this medicine. This medicine may affect certain medical test results.

Possible Side Effects While Using This Medicine

Call your doctor right away if you notice any of these side effects:

  • Allergic reaction: Itching or hives, swelling in your face or hands, swelling or tingling in your mouth or throat, chest tightness, trouble breathing
  • Severe rash, hives, or itching.
  • Swollen or sore tongue.
  • Unexplained fever or sore throat.
  • Unusual bleeding or bruising.

If you notice these less serious side effects, talk with your doctor:

  • Muscle twitching.
  • Nausea, diarrhea, or vomiting.

If you notice other side effects that you think are caused by this medicine, tell your doctor

Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088

Version Info

  • Last reviewed on 7/4/2015

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