Skip to main content


Generic name: trimethoprimtrye-METH-oh-prim ]
Drug class: Urinary anti-infectives

Medically reviewed by on Mar 16, 2023. Written by Cerner Multum.

What is Primsol?

Primsol is an antibiotic that is used to treat bladder or kidney infections, or ear infections caused by certain bacteria.

Primsol may also be used for purposes not listed in this medication guide.


You should not use Primsol if you have anemia caused by a folate (folic acid) deficiency.

Before taking this medicine

You should not use Primsol if you are allergic to it, or if you have:

  • anemia (low red blood cells) caused by a folate (folic acid) deficiency.

Primsol is not approved for use by anyone younger than 2 months old. This medicine should not be used to treat an ear infection in a child younger than 6 months old.

Tell your doctor if you have ever had:

  • a folate deficiency;

  • liver or kidney disease; or

  • a blood disorder.

Tell your doctor if you are pregnant. Primsol can interfere with your body's ability to metabolize folic acid, a form of vitamin B important in the development of the unborn baby's brain and spinal cord.

It may not be safe to breastfeed while using this medicine. Ask your doctor about any risk.

How should I take Primsol?

Follow all directions on your prescription label and read all medication guides or instruction sheets. Use the medicine exactly as directed.

Measure liquid medicine carefully. Use the dosing syringe provided, or use a medicine dose-measuring device (not a kitchen spoon).

Use Primsol for the full prescribed length of time, even if your symptoms quickly improve. Skipping doses can increase your risk of infection that is resistant to medication. This medicine will not treat a viral infection such as the flu or a common cold.

This medicine can affect the results of certain medical tests. Tell any doctor who treats you that you are taking Primsol.

Store at room temperature away from moisture, heat, and light.

What happens if I miss a dose?

Take the medicine as soon as you can, but skip the missed dose if it is almost time for your next dose. Do not take two doses at one time.

What happens if I overdose?

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.

Overdose symptoms may include nausea, vomiting, headache, dizziness, confusion, depression, fever, chills, or flu-like symptoms.

Overdose can occur slowly over a long period of time if your daily doses are too high.

What should I avoid while taking Primsol?

Antibiotic medicines can cause diarrhea, which may be a sign of a new infection. If you have diarrhea that is watery or bloody, call your doctor before using anti-diarrhea medicine.

Primsol side effects

Get emergency medical help if you have signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

Primsol may cause serious side effects. Call your doctor at once if you have:

  • severe stomach pain, diarrhea that is watery or bloody (even if it occurs months after your last dose);

  • pale, gray, or bluish skin;

  • fever, weakness;

  • sore or swollen tongue;

  • easy bruising, purple or red spots under your skin;

  • a skin rash, no matter how mild; or

  • high potassium level--nausea, weakness, tingly feeling, chest pain, irregular heartbeats, loss of movement.

Common side effects of Primsol may include:

  • vomiting, diarrhea, stomach pain;

  • rash, itching; or

  • swelling in your tongue.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

What other drugs will affect Primsol?

Other drugs may affect Primsol, including prescription and over-the-counter medicines, vitamins, and herbal products. Tell your doctor about all your current medicines and any medicine you start or stop using.

Frequently asked questions

Further information

Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use this medication only for the indication prescribed.

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.