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Generic name: vancomycin (oral) [ VAN-koe-MYE-sin ]
Brand names: FIRST-Vancomycin 25, FIRST-Vancomycin 50, Firvanq
Drug class: Glycopeptide antibiotics

Medically reviewed by on Sep 14, 2022. Written by Cerner Multum.

What is Firvanq?

Firvanq is an antibiotic. Oral (taken by mouth) this medicine fights bacteria in the intestines.

Firvanq is used to treat an infection of the intestines caused by Clostridium difficile, which can cause watery or bloody diarrhea. This medicine is also used to treat staph infections that can cause inflammation of the colon and small intestines.

Oral Firvanq works only in the intestines and is not normally absorbed into the body. Firvanq will not treat other types of infection. An injection form of vancomycin is available to treat serious infections in other parts of the body.

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


Oral Firvanq works only in the intestines and will not treat infections in other parts of the body. Follow all directions on your medicine label and package. Tell each of your healthcare providers about all your medical conditions, allergies, and all medicines you use.

Before taking this medicine

You should not Firvanq if you are allergic to it.

Tell your doctor if you have ever had:

Tell your doctor if you are pregnant or breastfeeding.

How should I take Firvanq?

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

Taking more of Firvanq will not make it more effective, and may cause serious or life-threatening side effects.

Shake the oral solution (liquid) before you measure a dose. Use the dosing syringe provided, or use a medicine dose-measuring device (not a kitchen spoon).

Use this medicine 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. Firvanq will not treat a viral infection such as the flu or a common cold.

If you use this medicine long-term, you may need frequent medical tests.

Store Firvanq capsules at room temperature, away from heat and moisture.

Store the liquid medicine in the refrigerator, do not freeze. Throw away any unused liquid after 14 days.

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.

What should I avoid while using Firvanq?

Follow your doctor's instructions about any restrictions on food, beverages, or activity.

Firvanq 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.

Certain side effects may occur if your body absorbs Firvanq through the intestinal walls. Call your doctor at once if you have:

  • increased diarrhea that is watery or bloody;

  • hearing loss, ringing in your ears;

  • kidney problems--swelling, rapid weight gain, pain in your side or lower back, little or no urination; or

  • low potassium level--leg cramps, constipation, irregular heartbeats, fluttering in your chest, increased thirst or urination, numbness or tingling, muscle weakness or limp feeling.

Side effects on the kidneys may be more likely in older adults taking Firvanq.

Common side effects of Firvanq may include:

  • low potassium;

  • nausea; or

  • stomach pain.

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 Firvanq?

Other drugs may affect Firvanq, 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.