Flucytosine

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Generic Name: Flucytosine Brand Name(s): Generics only. No brands available.

Uses

What is Flucytosine used for?

Flucytosine is commonly 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.

How should I take Flucytosine?

Take this medication by mouth, usually 4 times a day (every 6 hours), or as directed by your doctor. 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. Therefore, 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 allow the fungus to continue to grow, which may result in a return of the infection.

Tell your doctor right away if your condition persists or worsens.

How do I store Flucytosine?

Flucytosine is best stored at room temperature away from direct light and moisture. To prevent drug damage, you should not store Flucytosine in the bathroom or the freezer. There may be different brands of Flucytosine that may have different storage needs. It is important to always check the product package for instructions on storage, or ask your pharmacist. For safety, you should keep all medicines away from children and pets.

You should not flush Flucytosine down the toilet or pour them into a drain unless instructed to do so. It is important to properly discard this product when it is expired or no longer needed. Consult your pharmacist for more details about how to safely discard your product.

Precautions & warnings

What should I know before using Flucytosine?

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, a low number of blood cells (red or white blood cells, platelets), radiation treatment, mineral imbalance (such as low level of potassium in the blood).

Wash your hands well to prevent the spread of infection. Avoid contact with people who have infections that may spread to others (such as chickenpox, measles, flu). Consult your doctor if you have been exposed to an infection or for more details.

Do not have immunizations/vaccinations without the consent of your doctor. 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.

Kidney function declines as you grow older. This medication is removed by the kidneys. Therefore, older adults may be more sensitive to the side effects of this drug.

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 not known whether this drug passes into breast milk. It may have undesirable effects on a nursing infant. Breast-feeding while using this drug is not recommended. Consult your doctor before breast-feeding.

Is it safe during pregnancy or breast-feeding?

There are no adequate studies in women for determining risk when using this Flucytosine during pregnancy or while breastfeeding. Please always consult with your doctor to weigh the potential benefits and risks before taking Flucytosine. Flucytosine is pregnancy risk category C according to the US Food and Drug Administration (FDA).

FDA pregnancy risk category reference below:

  • A=No risk,
  • B=No risk in some studies,
  • C=There may be some risk,
  • D=Positive evidence of risk,
  • X=Contraindicated,
  • N=Unknown

Side effects

What side effects can occur from Flucytosine?

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

Remember that your doctor has prescribed this medication because he or she 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 any of these unlikely but serious side effects occur: signs of kidney problems (such as change in the amount of urine), signs of liver problems (such as persistent nausea/vomiting, 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 fever, chills, cough, persistent sore throat), 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, seek immediate medical attention if you notice any symptoms of a serious allergic reaction, including: rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing.

Not everyone experiences these side effects. There may be some side effects not listed above. If you have any concerns about a side-effect, please consult your doctor or pharmacist.

Interactions

What drugs may interact with Flucytosine?

Some products that may interact with this drug include: 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 laboratory tests (including serum creatinine), possibly causing false test results. Make sure laboratory personnel and all your doctors know you use this drug.

Flucytosine may interact with other drugs that you are currently taking, which can change how your drug works or increase your risk for serious side effects. To avoid any potential drug interactions, you should keep a list of all the drugs you are using (including prescription drugs, nonprescription drugs and herbal products) and share it with your doctor and pharmacist. For your safety, do not start, stop, or change the dosage of any drugs without your doctor’s approval.

Does food or alcohol interact with Flucytosine?

Flucytosine may interact with food or alcohol by altering the way the drug works or increase the risk for serious side effects. Please discuss with your doctor or pharmacist any potential food or alcohol interactions before using this drug.

What health conditions may interact with Flucytosine?

Flucytosine may interact with your health condition. This interaction may worsen your health condition or alter the way the drug works. It is important to always let your doctor and pharmacist know all the health conditions you currently have.

Dosage

The information provided is not a substitute for any medical advice. You should ALWAYS consult with your doctor or pharmacist before using this Flucytosine.

What is the dose of Flucytosine for an adult?

Usual Adult Dose for Candida Urinary Tract Infection

Serious infections due to susceptible strains of Candida and/or Cryptococcus (including septicemia, endocarditis, urinary system infections, meningitis, and pulmonary infections): 50 to 150 mg/kg/day orally in divided doses every 6 hours (in conjunction with amphotericin B)

Alternatively, the Infectious Diseases Society of America (IDSA) recommends a dosage of 100 mg/kg/day orally in 4 divided doses (in conjunction with amphotericin B or fluconazole).

Usual Adult Dose for Candidemia

Serious infections due to susceptible strains of Candida and/or Cryptococcus (including septicemia, endocarditis, urinary system infections, meningitis, and pulmonary infections): 50 to 150 mg/kg/day orally in divided doses every 6 hours (in conjunction with amphotericin B)

Alternatively, the Infectious Diseases Society of America (IDSA) recommends a dosage of 100 mg/kg/day orally in 4 divided doses (in conjunction with amphotericin B or fluconazole).

Usual Adult Dose for Cryptococcal Meningitis – Immunocompetent Host

Serious infections due to susceptible strains of Candida and/or Cryptococcus (including septicemia, endocarditis, urinary system infections, meningitis, and pulmonary infections): 50 to 150 mg/kg/day orally in divided doses every 6 hours (in conjunction with amphotericin B)

Alternatively, the Infectious Diseases Society of America (IDSA) recommends a dosage of 100 mg/kg/day orally in 4 divided doses (in conjunction with amphotericin B or fluconazole).

Usual Adult Dose for Cryptococcal Meningitis – Immunosuppressed Host

Serious infections due to susceptible strains of Candida and/or Cryptococcus (including septicemia, endocarditis, urinary system infections, meningitis, and pulmonary infections): 50 to 150 mg/kg/day orally in divided doses every 6 hours (in conjunction with amphotericin B)

Alternatively, the Infectious Diseases Society of America (IDSA) recommends a dosage of 100 mg/kg/day orally in 4 divided doses (in conjunction with amphotericin B or fluconazole).

Usual Adult Dose for Cryptococcosis

Serious infections due to susceptible strains of Candida and/or Cryptococcus (including septicemia, endocarditis, urinary system infections, meningitis, and pulmonary infections): 50 to 150 mg/kg/day orally in divided doses every 6 hours (in conjunction with amphotericin B)

Alternatively, the Infectious Diseases Society of America (IDSA) recommends a dosage of 100 mg/kg/day orally in 4 divided doses (in conjunction with amphotericin B or fluconazole).

Usual Adult Dose for Fungal Endocarditis

Serious infections due to susceptible strains of Candida and/or Cryptococcus (including septicemia, endocarditis, urinary system infections, meningitis, and pulmonary infections): 50 to 150 mg/kg/day orally in divided doses every 6 hours (in conjunction with amphotericin B)

Alternatively, the Infectious Diseases Society of America (IDSA) recommends a dosage of 100 mg/kg/day orally in 4 divided doses (in conjunction with amphotericin B or fluconazole).

Usual Adult Dose for Systemic Fungal Infection

Serious infections due to susceptible strains of Candida and/or Cryptococcus (including septicemia, endocarditis, urinary system infections, meningitis, and pulmonary infections): 50 to 150 mg/kg/day orally in divided doses every 6 hours (in conjunction with amphotericin B)

Alternatively, the Infectious Diseases Society of America (IDSA) recommends a dosage of 100 mg/kg/day orally in 4 divided doses (in conjunction with amphotericin B or fluconazole).

Renal Dose Adjustments

CrCl 20 to 40 mL/min: 12.5 to 37.5 mg/kg orally every 12 hours

CrCl 10 to 20 mL/min: 12.5 to 37.5 mg/kg orally every 24 hours

CrCl less than 10 mL/min: 12.5 to 37.5 mg/kg orally every 24 to 48 hours or longer, depending on serum drug concentrations

Precautions

Use flucytosine with extreme caution in patients with impaired renal function. Since flucytosine is excreted primarily by the kidneys, renal impairment may lead to accumulation of the drug. Flucytosine levels should be monitored to determine the adequacy of renal excretion in such patients. Dosage adjustments should be made in patients with renal impairment to prevent progressive accumulation of active drug. Close monitoring of renal status of all patients is essential.

Flucytosine must be given with extreme caution in patients with bone marrow depression. Patients may be more prone to bone marrow suppression if they have a hematologic disease, are being treated with radiation or other drugs which depress bone marrow, or have a history of treatment with such drugs or radiation. Bone marrow toxicity can be irreversible and may lead to death in immunosuppressed patients. Close monitoring of hematologic status of all patients is essential.

Peak blood concentrations of flucytosine should not exceed 100 mcg/mL. Prolonged serum levels in excess of 100 mcg/mL may be associated with an increased risk of toxicity, especially gastrointestinal (diarrhea, nausea, vomiting), hematologic (leukopenia, thrombocytopenia), and hepatic (hepatitis).

Close monitoring of hepatic (alkaline phosphatase, SGOT, and SGPT) and electrolytes status of all patients is essential.

The safety and efficacy of flucytosine have not been systematically studied in pediatric patients. A small number of neonates have been treated with 25 to 200 mg/kg/day of flucytosine, with and without the addition of amphotericin B therapy, for systemic candidiasis. No unexpected side effects were reported in these patients. It should be noted, however, that hypokalemia and acidemia were observed in one patient who received flucytosine in combination with amphotericin B, and anemia was observed in a second patient who received flucytosine alone. Transient thrombocytopenia was observed in two additional patients, one of whom also received amphotericin B therapy.

Dialysis

Patients undergoing hemodialysis every 48 to 72 hours: 20 to 50 mg/kg orally following dialysis session

Flucytosine is dialyzable (50% to 100%). The dose should be given post hemodialysis.

Other Comments

Nausea or vomiting may be reduced or avoided if the capsules are given a few at a time over a 15 minute period.

Flucytosine should be used in conjunction with amphotericin B for the treatment of systemic candidiasis and cryptococcosis due to the emergence of resistance to flucytosine. In patients who cannot receive amphotericin B, oral fluconazole may be administered with flucytosine.

The duration of therapy depends on the nature and severity of the infection.

What is the dose of Flucytosine for a child?

Usual Pediatric Dose for Systemic Fungal Infection

Serious infections due to susceptible strains of Candida and/or Cryptococcus (including septicemia, endocarditis, urinary system infections, meningitis, and pulmonary infections):

Less than 1 month: 25 to 100 mg/kg/day orally in divided doses every 12 to 24 hours (in conjunction with amphotericin B) has been suggested

1 month to 18 years: 50 to 150 mg/kg/day orally in divided doses every 6 hours (in conjunction with amphotericin B) has been suggested

How is Flucytosine available?

Flucytosine is available in the following dosage forms and strengths:

  • Oral Capsule

What should I do in case of an emergency or overdose?

In case of an emergency or an overdose, call your local emergency services or go to your nearest emergency room.

What should I do if I miss a dose?

If you miss a dose of Flucytosine, take it as soon as possible. However, if it is almost time for your next dose, skip the missed dose and take your regular dose as scheduled. Do not take a double dose.

Hello Health Group does not provide medical advice, diagnosis or treatment.

Review Date: February 1, 2018 | Last Modified: February 1, 2018

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