Flucytosine (oral)


Flucytosine is a medication that helps fight fungal infections. It is in a class of medications known as antifungal medications.

Flucytosine helps treat severe fungal infections involving the blood, heart, lungs, urinary tract, and central nervous system.

This medication is occasionally given together with another medication known as amphotericin B. It may also serve other purposes not covered in this medicine guide.

Conditions Treated

  • Cryptococcus fungal infection
  • Candida infection
  • Urinary tract infection
  • Candidiasis yeast infection
  • Cryptococcal infection
  • Chromoblastomycosis

Type Of Medicine

  • Antifungal

Side Effects

In addition to its useful effects, Flucytosine may cause certain undesirable effects. While not all of the effects below may happen, those that happen may require medical attention.

See your doctor promptly if you develop any of the side effects listed below:

More common:

Less common:

Hypersensitivity of skin to the sun

  • Confusion

Hallucinations (feeling, hearing, or seeing things that aren't there)

Some Flucytosine side effects may happen that normally don't require medical care. These effects may vanish during treatment while you adjust to Flucytosine. Moreover, your healthcare provider may help you find ways to decrease or prevent some of the effects.

Please see your healthcare provider if you've got questions about some of the effects below, if they're troublesome, or if they persist.

More common:

  • Diarrhea
  • Loss of appetite
  • Abdominal pain
  • Nausea or vomiting

Less common:

Other Flucytosine side effects not mentioned above may occur in some people too. If you develop any other effects, please check with your physician.

Tell your physician or other healthcare provider if your symptoms get worse or don't begin to improve. Some fungal diseases need to be treated for several weeks or months to heal.

This medication can increase your sensitivity to the sun. Stay away from the sun. Otherwise, use sunscreen and wear protective clothing. Don't use tanning booths/beds or sun lamps.

You may become dizzy or drowsy while using Flucytosine. Don't use machinery, drive, or carry out any task that requires alertness until you understand how Flucytosine affects you. Don't sit or stand up quickly, particularly if you're a little older. This decreases the risk of fainting or dizzy spells.


Follow all directions on the prescription label. Don't take Flucytosine in smaller or larger quantities or for a longer period than recommended.

While taking Flucytosine, you may require frequent blood tests.

Take each Flucytosine dose with eight ounces (1 full glass) of water.

Take Flucytosine orally (by mouth), normally every 6 hours or 4 times daily, or as ordered by your physician. To relieve an upset stomach, don't swallow all the capsules for a single dose at once. It may be wise to swallow them in a 15-minute spell for every dose until you finish the full dose.

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

Flucytosine works best when you keep its level constant in your body. Thus, take Flucytosine at evenly spaced times. Take the drug at the same intervals each day.

Don't stop taking Flucytosine until you finish the whole prescribed amount, even if your symptoms clear in a matter of days. Stopping Flucytosine prematurely may let the fungus continue to grow, possibly bringing back the infection.

Tell your physician promptly if your condition gets worse or persists.

Flucytosine may cause vomiting and nausea. If you use more than a single capsule in one dose, swallow a single capsule after the other in a 15-minute spell to help prevent vomiting and nausea.

Skipping Flucytosine doses can raise your risk of additional infection that doesn't respond to antifungal medication. Flucytosine won't treat viral infections like a common cold or flu.

If you think there's an overdose of Flucytosine, get medical attention urgently or call the poison helpline: 1-800-222-1222. Overdose symptoms can include vomiting, nausea, diarrhea, unusual bleeding/bruising, or upper stomach pain.


The effects of certain medications may change if you use other medications or herbs all at once. This can raise your risk for severe side effects or can make your medications not work properly. The following medication interactions may occur, but don't always occur. Your pharmacist or doctor may control or prevent interactions by closely monitoring or altering how you take your drugs.

To help your pharmacist and doctor provide you with the best care, make sure to let them know about all products you take (including prescription, over-the-counter, and herbal medicines) before beginning treatment with Flucytosine. While using Flucytosine, do not begin, discontinue, or adjust the dose of any other medications you're taking without your healthcare professional's knowledge.

Some products that can interact with Flucytosine include cytarabine, other medications that can affect the kidneys (such as NSAIDs like naproxen or ibuprofen), medications that reduce your blood cell count or weaken your immune system (including trimethoprim/sulfamethoxazole, cancer chemotherapy) or reduce bone marrow function.

This medicine may interfere with some lab tests (such as serum creatinine), potentially producing false results. Be sure to let all your healthcare professionals and lab personnel know you use Flucytosine.

This section doesn't contain all potential drug interactions. Have a full list of all products you take and give your pharmacist and doctor this list to lower your risk for severe medication problems.


Before using Flucytosine, inform your pharmacist and doctor if you have an allergy to it, or have other different allergies. Flucytosine may have inactive ingredients, which may cause allergies or other issues. For more details, consult your pharmacist.

Before using Flucytosine, reveal your medical history to your pharmacist and doctor, especially of: liver problems, kidney problems, low blood cell count (platelets, white or red blood cells), mineral imbalance (like low potassium levels in the blood), and radiation treatment.

Your physician should regularly check your progress to ensure that Flucytosine doesn't cause undesirable effects.

Flucytosine may bring about blood problems, which may increase the risk of bleeding gums, slow healing, and infection. Thus, you should be cautious when using standard toothbrushes, toothpicks, and dental floss. Whenever possible, dental work should be carried out before you start using Flucytosine or put off until your blood cell counts are back to normal. Please check with your dentist or medical doctor if you've got any questions about good mouth care (oral hygiene) during treatment.

Flucytosine may make your skin become more sensitive to the sun than it normally is. Getting exposed to the sun, even for short periods of time, can cause redness, itching, skin rash, severe sunburn, or other discoloration of the skin. When you start taking Flucytosine:

  • If possible, stay away from direct sunlight, particularly in the hours between 10 am and 3 pm.
  • Wear sunglasses. Also wear protective clothes, including a hat.
  • Apply a sunscreen product with an SPF (skin protection factor) of 15 or more. Some patients, especially those of a fair complexion, may require a sunscreen product with a bigger SPF number. If you've got questions about this, ask your healthcare professional.
  • Don't use a tanning booth, bed or sunlamp.

If you suffer a severe reaction from staying in the sun, see your doctor.

Flucytosine may also make some people dizzy, drowsy, lightheaded, or less attentive than they usually are. Make sure you understand how you respond to Flucytosine before you use machines, drive, or carry out any task that might be hazardous if you're not alert or are dizzy. If these symptoms are particularly bothersome, report them to your doctor.

Wash your hands properly to stop the infection from spreading. Avoid contact with anyone who has infections that can spread to other people (such as flu, measles, chickenpox). Consult your doctor for more details or if you've been exposed to any infection.

Don't have vaccinations/immunizations without your doctor's consent. Avoid contact with anyone who has recently had live vaccines (e.g. flu vaccine inhaled via the nose).

To reduce the risk of getting cut, injured, or bruised, be careful when using sharp objects like nail cutters and razors, and avoid activities like contact sports.

Kidney function weakens as you get older. The kidneys help to get rid of this medication. Thus, the elderly may be more vulnerable to the effects of Flucytosine.

During pregnancy, Flucytosine should only be taken when it's absolutely necessary. Flucytosine shouldn't be used during the first trimester (first three months of pregnancy) as it can harm the fetus. Discuss the benefits and risks of Flucytosine with your doctor.

It's not known whether Flucytosine gets into human milk. However, it could have adverse effects on a breastfeeding baby. You should not breastfeed while using Flucytosine. Consult your physician before breastfeeding.

Although there isn't any specific data comparing Flucytosine use in kids or the elderly with intake in other ages, this medication is unlikely to cause children or the elderly different problems or effects than it does adults.


Keep Flucytosine at 25 degrees Celsius. You can store the capsules temporarily at 15 to 30 degrees Celsius.

Don't use this medication if its original seal on top of the container is missing or broken.

Dispose of Flucytosine that's expired (out of date) or once you no longer need it. Keep Flucytosine out of children's reach.


You shouldn't use this medication if you have allergies to it. To ensure it is safe to use Flucytosine, inform your physician if you have:

  • A bone marrow disease or blood cell disorder
  • Kidney disease
  • An electrolyte imbalance (e.g. low potassium levels in your blood)
  • Weak immune system (due to radiation or use of medication that brings about bone marrow suppression)
  • You may be unable to take this medication or may need special monitoring or a dosage adjustment if you've got any of the above conditions.

It's unknown whether Flucytosine will harm an unborn child. Don't take this medicine without consulting your doctor first if you're expectant or could get pregnant during treatment.

It's unknown whether Flucytosine gets into human milk. However, don't take Flucytosine without consulting your doctor first if you're nursing an infant.

Exercise extreme caution in people with damaged renal function. It's essential to closely monitor the renal, hepatic, and hematologic conditions of all patients. Be sure to review these instructions before using Flucytosine.

Even if you start to feel better, use all of the medicine that's been prescribed for you. Your symptoms may start to ease before your infection is fully treated.

Flucytosine may cause vomiting and nausea. You can ease this effect by using a few capsules at a time in a 15-minute period.

Patients treated with medications that compromise bone marrow function (such as cytostatics) will need to be carefully treated. Blood cell counts will need to be taken frequently.