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Generic name: flucytosine [ floo-SYE-toe-seen ]
Brand name: Ancobon
Dosage form: oral capsule (250 mg; 500 mg)
Drug class: Miscellaneous antifungals

Medically reviewed by on Feb 29, 2024. Written by Cerner Multum.

What is flucytosine?

Flucytosine is an antifungal medication that fights infections caused by fungus.

Flucytosine is used to treat serious fungal infections of the blood, lungs, heart, central nervous system, and urinary tract.

Flucytosine is sometimes given with another medicine called amphotericin B.

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

Flucytosine 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.

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

Common side effects of flucytosine may include:

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.


Before you take flucytosine, tell your doctor if you have kidney disease.

Before taking this medicine

You should not use flucytosine if you are allergic to it.

To make sure flucytosine is safe for you, tell your doctor if you have:

It is not known whether flucytosine will harm an unborn baby. Tell your doctor if you are pregnant or plan to become pregnant.

It is not known whether flucytosine passes into breast milk or if it could harm a nursing baby. You should not breast-feed while using this medicine.

How should I take flucytosine?

Follow all directions on your prescription label. Do not take this medicine in larger or smaller amounts or for longer than recommended.

While using flucytosine, you may need frequent blood tests.

Take each dose with a full glass (8 ounces) of water.

Flucytosine may cause nausea and vomiting. If you take more than one capsule per dose, swallow one capsule at a time over a 15-minute period to help prevent nausea and vomiting.

Use this medicine for the full prescribed length of time. Your symptoms may improve before the infection is completely cleared. Skipping doses may also increase your risk of further infection that is resistant to antifungal medicine. Flucytosine will not treat a viral infection such as the flu or a common cold.

Store at room temperature away from moisture and heat.

What happens if I miss a dose?

Take the missed dose as soon as you remember. Skip the missed dose if it is almost time for your next scheduled dose. Do not take extra medicine to make up the missed dose.

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, diarrhea, upper stomach pain, or unusual bleeding or bruising.

What should I avoid while taking flucytosine?

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

What other drugs will affect flucytosine?

Tell your doctor about all your current medicines and any you start or stop using, especially:

This list is not complete. Other drugs may interact with flucytosine, including prescription and over-the-counter medicines, vitamins, and herbal products. Not all possible interactions are listed in this medication guide.

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.