Flucytosine is used to treat serious fungal infections in the body. It belongs to a class of drugs known as antifungal drugs. It is often used with other medications. It works by slowing the growth of certain types of fungus.

Take this medication by mouth as directed by your doctor, usually 4 times a day (every 6 hours). To reduce stomach upset, do not swallow all of the capsules for one dose at the same time. It may be best to swallow the capsules for each dose over a 15-minute period until the full dose is taken.

The dosage is based on your medical condition, weight, and response to treatment.

This medication works best when the amount of drug in your body is kept at a constant level. Take this drug at evenly spaced intervals. To help you remember, take it at the same times each day.

Continue to take this medication until the full prescribed amount is finished, even if symptoms disappear after a few days. Stopping the medication too early may result in a return of the infection.

Tell your doctor right away if your condition lasts or gets worse.

Nausea, vomiting, or diarrhea may occur. See the How to Use section about how to reduce stomach upset. If any of these effects last or get worse, tell your doctor or pharmacist promptly.

Remember that this medication has been prescribed because your doctor has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.

Tell your doctor right away if you have any serious side effects, including:

• signs of kidney problems (such as change in the amount of urine)
• signs of liver problems (such as nausea/vomiting that doesn't stop, stomach/abdominal pain, dark urine, yellowing eyes/skin)
• signs of anemia (such as unusual tiredness, fast breathing, pale skin, fast heartbeat)
• signs of infection (such as sore throat that doesn't go away, fever, chills, cough)
• signs of bleeding (such as easy bruising/bleeding, nose bleeds, bleeding gums, bloody/black/tarry stools, vomit that looks like coffee grounds)
• muscle weakness/cramping

A very serious allergic reaction to this drug is rare. However, get medical help right away if you notice any symptoms of a serious allergic reaction, including:

• rash
• itching/swelling (especially of the face/tongue/throat)
• severe dizziness
• trouble breathing

This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.

In the US - Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088 or at www.fda.gov/medwatch.

In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.

Before taking flucytosine, tell your doctor or pharmacist if you are allergic to it; or if you have any other allergies. This product may contain inactive ingredients, which can cause allergic reactions or other problems. Talk to your pharmacist for more details.

Before using this medication, tell your doctor or pharmacist your medical history, especially of:

• kidney problems
• liver problems
• decreased bone marrow function (low white, red or platelet blood counts)
• a certain metabolic disorder (DPD enzyme deficiency)
• radiation treatment
• mineral imbalance (such as low level of potassium in the blood)

Flucytosine can make you more likely to get infections or may make current infections worse. Stay away from anyone who has an infection that may easily spread (such as chickenpox, COVID-19, measles, flu). Talk to your doctor if you have been exposed to an infection or for more details.

Tell your health care professional that you are using flucytosine before having any immunizations/vaccinations. Avoid contact with people who have recently received live vaccines (such as flu vaccine inhaled through the nose).

To lower the chance of getting cut, bruised, or injured, use caution with sharp objects like razors and nail cutters, and avoid activities such as contact sports.

During pregnancy, this medication should be used only when clearly needed. This medication is not recommended for use during the first 3 months of pregnancy. It may harm an unborn baby. Discuss the risks and benefits with your doctor.

It is unknown if this drug passes into breast milk. Because of the possible risk to the infant, breastfeeding is not recommended while using this drug. Consult your doctor before breastfeeding.

Drug interactions may change how your medications work or increase your risk for serious side effects. This document does not contain all possible drug interactions. Keep a list of all the products you use (including prescription/nonprescription drugs and herbal products) and share it with your doctor and pharmacist. Do not start, stop, or change the dosage of any medicines without your doctor's approval.

Some products that may interact with this drug are:

• cytarabine
• other drugs that may affect the kidneys (including NSAIDs such as ibuprofen or naproxen)
• other drugs that decrease bone marrow function or lower your number of blood cells or weaken the immune system (such as cancer chemotherapy, trimethoprim/sulfamethoxazole)

This medication may interfere with certain lab tests (such as serum creatinine), possibly causing false test results. Make sure lab personnel and all your doctors know you use this drug.

If someone has overdosed and has serious symptoms such as passing out or trouble breathing, call 911. Otherwise, call a poison control center right away. US residents can call 1-800-222-1222. Canada residents can call 1-844-764-7669.

Do not share this medication with others.

Lab and/or medical tests (such as kidney/liver function, blood cell counts, blood mineral levels) should be done while you are taking this medication. Keep all medical and lab appointments. Consult your doctor for more details.

If you miss a dose, take it as soon as you remember. If it is near the time of the next dose, skip the missed dose. Take your next dose at the regular time. Do not double the dose to catch up.

Store at room temperature away from light and moisture. Do not store in the bathroom. Keep all medications away from children and pets.

Do not flush medications down the toilet or pour them into a drain unless instructed to do so. Properly discard this product when it is expired or no longer needed. Consult your pharmacist or local waste disposal company.