Ancobon (Flucytosine) - Oral


You should avoid taking Ancobon (flucytosine) if you have liver, kidney, or blood problems. While taking flucytosine, your healthcare provider will closely monitor your blood, liver, and kidneys to ensure that Ancobon is safe and effective.

What Is Ancobon?

Ancobon (flucytosine) is an antifungal drug used to treat fungal infections that have taken over various body systems caused by Candida or cryptococcus.

Ancobon works in the body by allowing the drug to be absorbed by the fungus causing the infection. Once inside the fungus, Ancobon stops it from producing and growing.

When taking flucytosine alone, the fungi have the potential to not respond to the medication, which prevents Ancobon from working. Therefore, flucytosine is often prescribed along with amphotericin B to lower the chances of resistance. Like Ancobon, amphotericin B is an antifungal drug; however, it can kill fungi instead of inhibiting growth. 

You can get flucytosine by prescription, which is available as a capsule taken by mouth.

Drug Facts

Generic Name: Flucytosine

Brand Name(s): Ancobon

Drug Availability: Prescription

Administration Route: Oral

Therapeutic Classification: Antifungal

Available Generically: Yes

Controlled Substance: N/A

Active Ingredient: Flucytosine

Dosage Form(s): Capsule

What Is Ancobon Used For?

The Food and Drug Administration (FDA) approved Ancobon to treat severe fungal infections in the heart, lungs, blood, spinal cord, and bladder caused by Candida or cryptococcus.

How to Take Ancobon 

You should take flucytosine as instructed by your healthcare provider and follow their directions as stated.

Ancobon is prescribed as a capsule to be taken by mouth with water. If you struggle with swallowing pills, you can request Ancobon in the form of a liquid taken by mouth.

Typically, the total daily dose is divided into four doses taken every six hours. To prevent an upset stomach or vomiting, you can take one capsule every 15 minutes until the full dose is taken. Furthermore, you should take the medication at the same time you do each day. Even if you feel better, do not stop taking flucytosine until your healthcare provider tells you to. 


Store Ancobon at room temperature (between 68 F and 77 F) and away from moisture. Storing your medication in hot and cold temperatures can prevent the medication from working correctly.

As always, ensure your medication is stored safely where children and pets cannot reach it to prevent accidental consumption. If you need more medication, contact your pharmacy or healthcare provider to request a refill.

Off-Label Uses

Healthcare providers may prescribe flucytosine for off-label uses, meaning for conditions not specifically indicated by the FDA.

For example, it may be used off-label to treat other infections caused by Candida, such as:

People who have HIV can use Ancobon to help treat Cryptococcus infections, such as:

Despite these indications not being approved by the FDA, there have been clinical studies showing flucytosine's effectiveness and safety for these uses.

How Long Does Ancobon Take to Work?

Ancobon takes about a few hours to start fighting the infection. However, it is important that you continue taking Ancobon until your healthcare provider tells you to stop. If you stop taking flucytosine too early, there is a risk that the fungal infection can return and prolong your recovery period. 

What Are the Side Effects of Ancobon?

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 pharmacist or a healthcare provider. You may report side effects to the FDA at or 800-FDA-1088.

Common Side Effects 

The following side effects are commonly reported while taking Ancobon:

  • Tiredness 
  • Dry mouth
  • Diarrhea
  • Upset stomach
  • Appetite loss
  • Headache

Severe Side Effects 

Do not hesitate to contact your healthcare provider immediately if you are experiencing any of these rare but serious side effects. Call 911 immediately if you feel your life is at risk or you need medical assistance.

Rare but severe side effects include:

  • Acute liver injury
  • Anemia
  • Agranulocytosis (extremely low number of granulocytes, a type of white blood cell)
  • Abnormal heartbeat
  • Chest pain
  • Shortness of breath
  • Hallucinations, tingling, or seizures
  • Hearing loss

This list does not contain all the possible severe effects, as reactions may differ from person to person. Contact your healthcare provider for more detailed information on the potential risk of severe side effects.

Long-Term Side Effects 

When taking Ancobon for an extended period, your healthcare provider will monitor your kidney and liver function through blood tests to ensure the medication isn't negatively affecting the kidney or liver.

Contact your healthcare provider or get medical attention immediately if you experience any signs of liver or kidney failure, such as:

  • Inability to pass urine
  • Change in urine amount
  • Blood in urine
  • Large weight gain
  • Dark urine
  • Light-colored stool
  • Yellowing of skin or eyes (jaundice)

Report Side Effects

Ancobon 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 or by phone (800-332-1088).

Dosage: How Much Ancobon Should I Take?

Drug Content Provided and Reviewed by IBM Micromedex®

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 form (capsules):
    • For fungus infections:
      • Adults—Dose is based on body weight and must be determined by your doctor. The dose is usually 50 to 150 milligrams (mg) per kilogram (kg) of body weight per day, taken every 6 hours.
      • Children—Use and dose must be determined by your doctor.


Certain factors may affect your dosage or how you take Ancobon, such as:

  • Difficulty swallowing pills: Ancobon can be made as a liquid suspension for those who have trouble swallowing pills. Do not try to open or break the capsules, as this can affect how the drug works in the body.
  • Age: If your children is prescribed Ancobon, their dosing will be dependent on body weight. Ask their healthcare provider how much they should be given.
  • Kidney problems: If you have a history of kidney problems or an existing kidney condition, your healthcare provider may adjust your dosage depending on your current kidney function.

Missed Dose

If you miss a dose, take the missed dose as soon as you remember. It is important that you only take one dose at a time, so do not take two doses at the same time to make up for the missed dose. Taking more than prescribed can increase the chance of unwanted side effects. 

Overdose: What Happens If I Take Too Much Ancobon?

There are limited reports of how much Ancobon can cause an overdose. However, you never exceed the recommended dosing as instructed by your healthcare provider to prevent an overdose or health complications.

Taking any amount greater per day can put you at risk of toxicities and serious adverse effects, including:

  • Gastrointestinal issues, such as nausea, vomiting, or diarrhea
  • Leukopenia (low white blood cell count), which can cause fever, fatigue, enlarged lymph nodes, enlarged liver or spleen, mucosal bleeding, and infections or sores that take longer to heal
  • Thrombocytopenia (low platelet count), with can cause nosebleeds, bleeding from the gums, blood in urine and stool, blood blisters, easy bruising, and petechiae (small red dots on the skin)
  • Hepatitis, which can cause fatigue, muscle pain, joint pain, fever, appetite loss, constant but mild pain in the upper right abdomen, and jaundice

Whether taking excess Ancobon was intentional or accidental, an overdose of flucytosine can be serious and cause severe adverse reactions. Contact the Poison Control Center or call 911 immediately if you or someone you know is experiencing severe symptoms of an overdose.

What Happens If I Overdose on Ancobon?

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

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


Drug Content Provided and Reviewed by IBM Micromedex®

It is very important that your doctor check your progress at regular visits to make sure this medicine is working properly. Blood and urine tests may be needed to check for unwanted effects.

Do not take other medicines unless thy 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 Ancobon?

Avoid taking Ancobon if you:

  • Have a history of or currently have kidney or liver failure
  • Have bone marrow depression
  • Are pregnant, as Ancobon can cause harm to the fetus in the first trimester. Therefore, it should not be used during the first trimester. However, there is no evidence of toxicity to the fetus in the second or third trimester, so it may be used with caution. Consult with your healthcare provider on the best course of action.
  • Are breastfeeding

What Other Medications Interact With Ancobon?

When taking Ancobon, certain other medications may affect how the drug works or increase your risk of side effects. Tell your healthcare provider about any other medications you take or plan to take, including over-the-counter (OTC) nonprescription products, vitamins, herbs, supplements, and plant-based medicines.

Avoid taking Ancobon with:

  • Porfimer, due to increased photosensitivity
  • Retrovir (zidovudine), due to the risk of decreased white blood cells
  • Cytarabine, as it can reduce how well flucytosine works

Talk with your pharmacist or healthcare provider for more detailed information about medication interactions with Ancobon.

What Medications Are Similar?

Since fungus can be prone to medication resistance, your healthcare provider will run tests to determine which medication will best fight the infection.

Other antifungal medications that are known to treat Candida fungal infections include:

  • Cancidas (caspofungin)
  • Diflucan (fluconazole)

According to the Infectious Diseases Society of America Guidelines, caspofungin is used as the first line of treatment when treating fungal infections caused by Candida. Compared with flucytosine, caspofungin can kill the fungus rather than inhibit growth. Fluconazole and caspofungin are often used in the early stages of Candida infection, while Ancobon is used as a later therapy option if both fail or fungal drug resistance develops. 

The first line of treatment for a cryptococcus infection is usually amphotericin B. Depending on the severity of the disease, amphotericin B can be given by itself or with Ancobon. 

This is a list of drugs also prescribed to treat fungal infections caused by Candida or cryptococcus. It is NOT necessarily a list of drugs recommended to take with Ancobon. Talk to your pharmacist or a healthcare provider if you have questions.

Frequently Asked Questions

  • Why is flucytosine taken with amphotericin B?

    Flucytosine is often prescribed with amphotericin B to lower the chances of resistance or when the fungal infection is not responding to the medication. If Ancobon is taken by itself, there is a chance the medication will not work due to fungal drug resistance.

  • Can I still take Ancobon if I have trouble swallowing pills?

    Yes, you can request a prescription for flucytosine as a suspension (liquid) that a pharmacist prepares. A suspension is a liquid form of the medication, so it can be easy for you to take it by mouth. If taking the capsule form, you should not crush or open the capsule as the medication may not work the same.

  • If I feel better, can I stop taking flucytosine?

    No, you should continue taking Ancobon until your healthcare provider tells you to stop. If you stop taking it too early, the fungus may not be fully treated and eliminated, which can increase the chances of fungal drug resistance. As a result, the infection will continue and will be harder to treat. 

How Can I Stay Healthy While Taking Ancobon?

To stay healthy while taking Ancoban, it is important to use the medication as directed by your healthcare provider. Even if you start feeling better, you must complete the full treatment time. If you stop using flucytosine too soon, your fungal infection could return and be more challenging to treat.

Since Ancoban is broken down by the liver and removed by the kidneys, your healthcare provider may perform blood tests to monitor their functioning. While blood tests can be a burden, they are important to properly assess whether this treatment is right for you.

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.

The author would like to recognize and thank Alexya Rosas for contributing to this article.

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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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