Firvanq (Vancomycin) - Oral

What Is Firvanq?

Firvanq (vancomycin) is an orally prescribed antibiotic medication used to treat infections of the gastrointestinal (GI) tract in people 18 and younger. This antibiotic is specifically approved to treat Clostridioides difficile-associated diarrhea and enterocolitis caused by Staphylococcus aureus (including methicillin-resistant strains).

Firvanq's primary ingredient, vancomycin, is commonly given as an injection to treat different infections; however, Firvanq itself is available as an oral liquid solution used to treat GI infections, specifically.

Notably, when Firvanq is taken by mouth, hardly any of the drug is absorbed into your bloodstream. Instead, it stays in your digestive tract, which is why it is used to treat infections in that area.

Firvanq is a prescription drug, which means your healthcare provider needs to write you an order for it. You will get the prescription filled by a pharmacy rather than purchasing it over-the-counter (OTC) from a drugstore or grocery store.

Vancomycin is also available under other brand names. Additionally, Vancocin is a brand-name product that contains Vancomycin. By itself, vancomycin is available as a generic product administered in the form of a liquid solution.

This article will focus on the oral use of vancomycin, referred to as Firvanq, a brand-name version of the drug.

Drug Facts

Generic Name: Vancomycin

Brand Name(s): Firvanq

Drug Availability: Prescription

Administration Route: Oral

Therapeutic Classification: Antibiotic

Available Generically: Yes

Controlled Substance: N/A

Active Ingredient: Vancomycin hydrochloride

Dosage Form(s): Liquid solution

What Is Firvanq Used For?

The Food and Drug Administration (FDA) approved Firvanq to treat Clostridioides difficile-associated diarrhea, often called C. diff, and enterocolitis caused by Staphylococcus aureus (S. aureus).

These conditions can cause symptoms that include:

It should be noted that C. diff is the bacteria that causes C. diff-associated diarrhea and C. diff colitis.

As such, C. diff is a germ (bacteria) that causes life-threatening diarrhea. It is usually a side-effect of taking antibiotics.

C. diff infections mostly occur in:

  • People 65 and older who take antibiotics and receive medical care
  • People staying in hospitals and nursing homes for a long period
  • People with weakened immune systems or previous infection with C. diff

Moreover, enterocolitis is an inflammation in a person's digestive tract. The condition specifically affects the inner lining of the small intestine and the colon, causing several symptoms. Enteritis is inflammation of the small intestine, while colitis is inflammation of the colon.

What's more, enterocolitis can be caused by a S. aureus infection. Often referred to as a "staph" infection, S. aureus is a type of germ that about 30% of people carry in their noses. Staph usually does not cause any harm; however, sometimes, staph causes infections. In healthcare settings, these staph infections can be serious or fatal.

Firvanq is also effective in the treatment of methicillin-resistant S. aureus (MRSA), which is a cause of staph infection that is difficult to treat because of resistance to some antibiotics.

How to Take Firvanq

Make sure to take Firvanq exactly as it is prescribed to you. It is usually taken three or four times a day for seven to 10 days. Even if you feel better, take the full amount of Firvanq prescribed.

Firvanq comes with two bottles: A bottle of powder and a bottle of liquid or diluent that is mixed with the powder to make the drug. This process is called reconstitution and is done at the pharmacy before receiving it.

You will get instructions with your medication on how much to take and how often to take it.


Store Firvanq liquid in the refrigerator (between 36 to 46 degrees F) with the lid kept on.

Traveling with refrigerated medications can complicate things somewhat, but there are steps you can take to keep your Firvanq at the right temperature. Pack it in a cooler or insulated container with an ice pack to keep it cold, and ensure your hotel or lodging will allow you access to a refrigerator.

Keep Firvanq packed in your carry-on luggage with the lid on tight so that pressure changes don’t cause leaks. The TSA allows medically necessary liquids and supplies, so you don’t have to worry about carry-on liquid restrictions.

Make sure to bring your prescription information and notify TSA personnel that you have the drug with you when you're going through security.

How Long Does Firvanq Take to Work?

You can expect to see symptoms improve within a couple of days after you begin taking Firvanq. If your symptoms worsen or don’t improve within a few days, give your healthcare provider a call.

What Are the Side Effects of Firvanq?

This is not a complete list of side effects, and others may occur. A healthcare provider can advise you on side effects. If you experience other effects, contact your healthcare provider. You may report side effects to the FDA at or 1-800-FDA-1088.

Common Side Effects

Common side effects include:

Severe Side Effects

Severe side effects caused by Firvanq are rare. Notify your healthcare provider right away if you notice these. Call 911 if your symptoms feel life-threatening or think you have a medical emergency.

Serious side effects and their symptoms can include the following:

  • Nephrotoxicity (kidney damage): Signs may include decreased urination or swelling in the legs, ankles, or feet due to retaining fluid.
  • Ototoxicity (hearing damage): This usually occurs in people who have already had some hearing loss or take vancomycin with another ototoxic drug. If you notice excessive ear ringing, dizziness, or vertigo, let your healthcare provider know as soon as possible.
  • Red-man syndrome: This condition is more likely with IV (intravenous or injected) vancomycin, but has been rarely reported with oral Firvanq. Symptoms include hypertension (high blood pressure), itching, shortness of breath, and flushing.

Long-Term Side Effects

Most nephrotoxicity and ototoxicity cases from Firvanq are mild and reversible. They will usually resolve shortly after discontinuing the medication.

Report Side Effects

Firvanq may cause other side effects. Call your healthcare provider if you have any unusual problems while taking this medication.

If you experience a serious side effect, you or your healthcare provider may send a report to the FDA's MedWatch Adverse Event Reporting Program online or by phone (800-332-1088).

Dosage: How Much Firvanq Should I Take?

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The dose of this medicine will be different for different patients. Follow your doctor's orders or the directions on the label. The following information includes only the average doses of this medicine. If your dose is different, do not change it unless your doctor tells you to do so.

The amount of medicine that you take depends on the strength of the medicine. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are using the medicine.

  • For oral dosage forms (capsules or oral liquid):
    • For treatment of C. difficile-associated diarrhea:
      • Adults—125 milligrams (mg) 4 times a day for 10 days.
      • Children—Dose is based on body weight and must be determined by the doctor. The usual dose is 40 milligrams per kilogram (mg/kg) of body weight, divided into 3 or 4 doses, and taken for 7 to 10 days. However, dose is usually not more than 2000 mg per day.
    • For treatment of Staphylococcal enterocolitis:
      • Adults—500 to 2000 milligrams (mg) divided into 3 or 4 doses for 7 to 10 days.
      • Children—Dose is based on body weight and must be determined by the doctor. The usual dose is 40 milligrams per kilogram (mg/kg) of body weight, divided into 3 or 4 doses, and taken for 7 to 10 days. However, dose is usually not more than 2000 mg per day.


Uses should be aware of the following before beginning Firvanq:

Firvanq is safe for use in children younger than 18 to treat C. diff.

Over half of the individuals in clinical trials for Firvanq were above age 65, and these older adults were more likely to develop kidney damage from the drug.

Frequent monitoring of kidney function during and after treatment with Firvanq should be a priority in older people. It may also take individuals of this age slightly longer to respond to vancomycin than younger adults.

Data on using oral Firvanq in pregnant people is limited but shows that the risk of harm to the baby is low. There is more data available for injectable vancomycin.

In that case, use is recommended in pregnant people only if the benefits outweigh the risks. Since vancomycin is often used for more serious infections, the benefits of taking it usually outweigh the risks.

Missed Dose

If you forget a dose of Firvanq, take it as soon as you remember. However, if you are closer to your next dose than the dose you missed, skip the missed dose and wait for your next scheduled one.

For example, if your schedule includes taking Firvanq at 7 a.m., 3 p.m., and 10 p.m., and you remember at 8 p.m. that you forgot your 3 p.m. dose, wait and take your usual 10 p.m. dose and continue as scheduled.

Overdose: What Happens If I Take Too Much Firvanq?

If you take Firvanq as directed, you shouldn’t be too concerned about using too much or overdosing. However, if you accidentally double up doses, continue your schedule as usual unless you notice any severe side effects like decreased urination, dizziness, or vertigo.

In that case, discontinue use until you speak to your healthcare provider. You might consider keeping a calendar and checking off each dose for the time period you will be taking Firvanq.

If a child or someone else in your household ingests Firvanq and you are concerned they may have taken an unsafe amount, contact the Poison Control Center.

If someone collapses or isn’t breathing, call 911.

What Happens If I Overdose on Firvanq?

If you think you or someone else may have overdosed on Firvanq, call a healthcare provider or the Poison Control Center (800-222-1222).

If someone collapses or isn't breathing after taking Firvanq, call 911 immediately.


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It is important that your doctor check you and your child's progress at regular visits to make sure that this medicine is working properly and that the colitis is cleared up completely. Blood, urine, and hearing tests may be needed to check for unwanted effects.

If you or your child's symptoms do not improve within a few days, or if they become worse, check with your doctor.

Check with your doctor right away if you or your child have blood in the urine, change in the frequency of urination or amount of urine, difficulty with breathing, nausea, vomiting, swelling of the feet or lower legs, or weakness during and after treatment with this medicine. These may be signs of a serious kidney problem.

Check with your doctor right away if you have sudden decrease in hearing or loss of hearing, which may be accompanied by dizziness and ringing in the ears. Tell your doctor if you or your child have dizziness or lightheadedness, feeling of constant movement of self or surroundings, or sensation of spinning. These may be symptoms of damage to your hearing or sense of balance.

This medicine may cause serious skin reactions, including toxic epidermal necrolysis, Stevens-Johnson syndrome, drug reaction with eosinophilia and systemic symptoms (DRESS), acute generalized exanthematous pustulosis (AGEP), and linear IgA bullous dermatosis (LABD). Check with your doctor right away if you have black, tarry stools, blistering, peeling, or loosening of the skin, chest pain, chills, cough, diarrhea, fever, itching, joint or muscle pain, painful or difficult urination, red irritated eyes, red skin lesions, often with a purple center, sore throat, sores, ulcers, or white spots in the mouth or on the lips, swollen glands, trouble breathing, unusual bleeding or bruising, or unusual tiredness or weakness.

If you are taking this medicine for diarrhea caused by other antibiotics, do not take any other diarrhea medicine without first checking with your doctor. Other medicines for diarrhea may make your diarrhea worse or make it last longer.

Do not take other medicines unless they have been discussed with your doctor. This includes prescription or nonprescription (over-the-counter [OTC]) medicines and herbal or vitamin supplements.

What Are Reasons I Shouldn't Take Firvanq?

You shouldn’t take Firvanq if you have an infection anywhere besides the digestive tract, such as a bloodstream infection, cellulitis (skin infection), or pneumonia (lung infection). Oral vancomycin will not treat these types of infections.

If you have a known allergy to vancomycin, you should not take Firvanq.

You should also inform any healthcare provider that may prescribe Firvanq for you if you have kidney disease or hearing damage, as the drug can potentially worsen those conditions.

What Other Medications Interact With Firvanq?

Since Firvanq does not get absorbed well into your bloodstream, it has less potential to interact with other drugs compared to injectable vancomycin.

A large family of drugs you still may want to watch out for and discuss with your healthcare provider is antibiotics. Oral vancomycin treats C. diff, which often happens due to overusing antibiotics in an attempt to treat other infections.

There is a chance you may still need other antibiotics to treat a different infection while you’re taking Firvanq. This isn’t a huge problem with most types of antibiotics but may increase your risk of side effects like nausea and vomiting.

Aminoglycosides are potent, broad-spectrum antibiotics that act through the inhibition of protein synthesis antibiotics include gentamicin, amikacin, tobramycin, neomycin, and streptomycin. Like vancomycin, these drugs are also ototoxic and nephrotoxic.

Taking any of these at the same time as Firvanq may increase your risk for hearing and/or kidney damage.

What Medications Are Similar?

Many drug classes of antibiotics exist, but vancomycin belongs to a class called glycopeptides.

The other antibiotics in the same class are:

  • Dalbavancin
  • Oritavancin
  • Telavancin

None of these drugs are available as an oral liquid like Firvanq. They are all injectable drugs given in the hospital for serious infections. Their chemical structure is similar to vancomycin, and they work to kill the same types of bacteria.

This list is not a list of drugs recommended to take with Firvanq. In fact, you should not take these drugs together. Ask your healthcare provider if you have questions.

Frequently Asked Questions

  • How does Firvanq work?

    Firvanq is a glycopeptide antibiotic that prevents infection-causing bacteria from properly forming their cell walls, which they cannot survive without.

    Firvanq is used for infections of the digestive tract because the properties of the drug molecule keep most of it contained there rather than entering your bloodstream.

  • What are the side effects of Firvanq?

    Common side effects of oral vancomycin are mostly limited to digestive issues like nausea, upset stomach, vomiting, flatulence, and diarrhea. It can also cause tinnitus, UTIs, or low potassium levels.

  • How long does it take for Firvanq to work?

    You should start seeing symptom improvement within a few days of beginning use. However, if following a few days of Firvanq use have gone by, and you still haven't seen any improvement, or especially if your symptoms worsen, you'll want to call your healthcare provider for instructions on how to proceed.

How Can I Stay Healthy While Taking Firvanq?

When dealing with digestive tract infections and severe diarrhea, working to stay hydrated and actively replacing lost electrolytes is essential. To do this, you can drink plenty of water (at least eight to 10 glasses per day) or consume electrolyte-replenishing drinks, such as Pedialyte.

Some research has also shown that taking probiotics, and maintaining a diet with plenty of soluble fiber, can help alleviate symptoms and promote recovery from C. diff.

Firvanq can often clear up symptoms within just a couple of days, and it’s easy to think that you don’t need to take the drug anymore if your diarrhea is gone.

However, it’s important to finish your prescribed length of treatment to prevent your symptoms from returning and to let the medication fully clear the infection.

Medical Disclaimer

Verywell Health's drug information is meant for educational purposes only and is not intended to replace medical advice, diagnosis, or treatment from a healthcare provider. Consult your healthcare provider before taking any new medication(s). IBM Watson Micromedex provides some of the drug content, as indicated on the page.

11 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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  2. MedlinePlus. Vancomycin.

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  4. Centers for Disease Control and Prevention. Clostridioides difficile infection.

  5. ScienceDirect. Enterocolitis.

  6. Centers for Disease Control and Prevention. Staphylococcus aureus in healthcare settings.

  7. Centers for Disease Control and Prevention. Methicillin-resistant Staphylococcus aureus (MRSA).

  8. Humphrey C, Veve MP, Walker B, Shorman MA. Long-term vancomycin use had low risk of ototoxicity. PLoS One. 2019;14(11):e0224561. doi:10.1371/journal.pone.0224561

  9. Krause KM, Serio AW, Kane TR, Connolly LE. Aminoglycosides: an overviewCold Spring Harb Perspect Med. 2016;6(6):a027029. doi:10.1101/cshperspect.a027029

  10. Blaskovich MAT, Hansford KA, Butler MS, Jia Z, Mark AE, Cooper MA. Developments in glycopeptide antibioticsACS Infect Dis. 2018;4(5):715-735. doi:10.1021/acsinfecdis.7b00258

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By Sara Hoffman, PharmD
Sara is a clinical pharmacist that believes everyone should understand their medications, and aims to achieve this through her writing.