Generic name: flucytosine [ floo-SYE-toe-seen ]
Drug class: Miscellaneous antifungals
Medically reviewed by Drugs.com. Last updated on Nov 14, 2023.
Use with extreme caution in patients with impaired renal function. Close monitoring of hematologic, renal, and hepatic status of all patients is essential .
Uses for flucytosine
Flucytosine is used in combination with other medicine (eg, amphotericin B) to treat serious fungus infections, including Candida infections (eg, septicemia, endocarditis, urinary tract infections) or Cryptococcus infections (eg, meningitis, lung infections). This medicine works by killing the fungus or preventing its growth.
This medicine is available only with your doctor's prescription.
Before using flucytosine
In deciding to use a medicine, the risks of taking the medicine must be weighed against the good it will do. This is a decision you and your doctor will make. For this medicine, the following should be considered:
Tell your doctor if you have ever had any unusual or allergic reaction to this medicine or any other medicines. Also tell your health care professional if you have any other types of allergies, such as to foods, dyes, preservatives, or animals. For non-prescription products, read the label or package ingredients carefully.
Appropriate studies have not been performed on the relationship of age to the effects of flucytosine in the pediatric population. Safety and efficacy have not been established.
No information is available on the relationship of age to the effects of flucytosine in geriatric patients.
There are no adequate studies in women for determining infant risk when using this medication during breastfeeding. Weigh the potential benefits against the potential risks before taking this medication while breastfeeding.
Interactions with Medicines
Although certain medicines should not be used together at all, in other cases two different medicines may be used together even if an interaction might occur. In these cases, your doctor may want to change the dose, or other precautions may be necessary. When you are taking this medicine, it is especially important that your healthcare professional know if you are taking any of the medicines listed below. The following interactions have been selected on the basis of their potential significance and are not necessarily all-inclusive.
Using this medicine with any of the following medicines is not recommended. Your doctor may decide not to treat you with this medication or change some of the other medicines you take.
Using this medicine with any of the following medicines is usually not recommended, but may be required in some cases. If both medicines are prescribed together, your doctor may change the dose or how often you use one or both of the medicines.
Interactions with Food/Tobacco/Alcohol
Certain medicines should not be used at or around the time of eating food or eating certain types of food since interactions may occur. Using alcohol or tobacco with certain medicines may also cause interactions to occur. Discuss with your healthcare professional the use of your medicine with food, alcohol, or tobacco.
Other Medical Problems
The presence of other medical problems may affect the use of this medicine. Make sure you tell your doctor if you have any other medical problems, especially:
- Blood disease or
- Bone marrow depression or
- Hypokalemia (low potassium in the blood) or
- Liver disease or
- Weak immune system—Use with caution. May make these conditions worse.
- Dihydropyrimidine dehydrogenase (DPD) enzyme deficiency (rare hereditary problem)—Should not be used in patients with this condition. May increase the risk of serious side effects (eg, drug toxicity).
- Kidney disease—Use with caution. The effects may be increased because of slower removal of the medicine from the body.
Proper use of flucytosine
Take this medicine exactly as directed by your doctor. Do not take more of it, do not take it more often, and do not take it for a longer time than your doctor ordered. To do so may increase the chance of side effects.
Keep using this medicine for the full treatment time, even if you feel better after the first few doses. Your infection may not clear up if you stop using the medicine too soon.
Swallow one capsule at a time over a 15 minute period to help prevent nausea and vomiting.
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.
- For fungus infections:
If you miss a dose of this medicine, take it as soon as possible. However, if it is almost time for your next dose, skip the missed dose and go back to your regular dosing schedule. Do not double doses.
Store the medicine in a closed container at room temperature, away from heat, moisture, and direct light. Keep from freezing.
Keep out of the reach of children.
Do not keep outdated medicine or medicine no longer needed.
Ask your healthcare professional how you should dispose of any medicine you do not use.
Precautions while using flucytosine
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.
Side Effects of flucytosine
Along with its needed effects, a medicine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.
Check with your doctor immediately if any of the following side effects occur:
Incidence not known
- black, bloody, tarry stools
- blistering, peeling, or loosening of the skin
- bloody or cloudy urine
- burning, crawling, itching, numbness, prickling, "pins and needles", or tingling feelings
- burning upper abdominal or stomach pain
- change in consciousness
- chest pain or tightness
- cough or hoarseness
- dark urine
- decreased urine output
- dry mouth
- feeling of constant movement of self or surroundings
- hearing loss
- hives, itching, skin rash
- increased sensitivity of the skin to sunlight
- irregular heartbeat
- joint or muscle pain
- light-colored stools
- loss of appetite
- loss of consciousness
- lower back or side pain
- mood changes
- muscle cramps or twitching
- no blood pressure or pulse
- no breathing
- numbness or tingling in the hands, feet, or lips
- painful or difficult urination
- pain in the lower back or side
- pale skin
- rapid weight gain
- rectal bleeding
- red irritated eyes
- red skin lesions, often with a purple center
- redness of the skin
- seeing, hearing, or feeling things that are not there
- sensation of spinning
- severe sunburn
- shakiness and unsteady walk
- sore throat
- sores, ulcers, or white spots on the lips or in the mouth
- stopping of the heart
- swelling of the face, ankles, or hands
- swollen glands
- trouble breathing
- unpleasant breath odor
- unsteadiness, trembling, or other problems with muscle control or coordination
- unusual bleeding or bruising
- unusual drowsiness, dullness, tiredness, weakness or feeling of sluggishness
- vomiting of blood or material that looks like coffee grounds
- weakness in the arms, hands, legs, or feet
- weight loss
- yellow eyes or skin
Other side effects not listed may also occur in some patients. If you notice any other effects, check with your healthcare professional.
Call your doctor for medical advice about side effects. You may report side effects to the FDA at 1-800-FDA-1088.
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