Pharmacologic class: Fluorinated pyrimidine analog
Therapeutic class: Antifungal
Pregnancy risk category C
Unclear. Thought to interfere with protein synthesis in cells of susceptible fungi after conversion to fluorouracil.
Capsules: 250 mg, 500 mg
Indications and dosages
➣ Severe fungal infections caused by susceptible strains of Candida species (including septicemia, endocarditis, urinary tract infections [UTIs]), and pulmonary infections) and Cryptococcus species (including meningitis, pulmonary infections, and UTIs)
Adults: 50 to 150 mg/kg P.O. daily in four equally divided doses q 6 hours
• Renal impairment (glomerular filtration rate below 50 ml/minute)
• Hypersensitivity to drug or other antifungals
Use cautiously in:
• renal impairment, underlying hepatic disease, bone marrow depression
• pregnant or breastfeeding patients
• children (safety not established).
• Give capsules a few at a time over 15 minutes to minimize nausea and vomiting.
• Know that drug is rarely used alone. Expect to give another antifungal or amphotericin B concurrently.
CNS: headache, dizziness, confusion, hallucinations, vertigo, psychosis, ataxia, paresthesia, parkinsonism, peripheral neuropathy
CV: chest pain, cardiac arrest
EENT: hearing loss
GI: nausea, vomiting, diarrhea, dyspepsia, ulcerative colitis, abdominal discomfort, anorexia, duodenal ulcer, hemorrhage
GU: azotemia, crystalluria, renal failure
Hematologic: eosinophilia, anemia, leukopenia, aplastic anemia, thrombocytopenia, bone marrow depression, agranulocytosis
Metabolic: hypokalemia, hypoglycemia
Respiratory: dyspnea, respiratory arrest
Skin: rash, pruritus, urticaria, photosensitivity
Drug-drug. Amphotericin B: synergistic effects, increased risk of toxicity
Drug-diagnostic tests. Alanine aminotransferase, alkaline phosphatase, aspartate aminotransferase, bilirubin, gamma-glutamyltransferase: increased levels
Glucose, granulocytes, hemoglobin, platelets, potassium, white blood cells: decreased levels
• Monitor kidney and liver function test results.
• Carefully monitor blood glucose level and hematologic test results.
☞ Assess for serious cardiovascular, renal, respiratory, and hematologic adverse reactions.
• Evaluate electrolyte levels, particularly potassium.
• Assess for signs and symptoms of bleeding.
• Advise patient to take capsules over 15-minute period to reduce GI upset.
☞ Instruct patient to immediately report unusual bleeding or bruising.
• Caution patient to avoid driving and other hazardous activities until he knows how drug affects concentration and alertness.
• Instruct patient to minimize GI upset by eating frequent, small servings of food and drinking adequate fluids.
• Advise female patient to inform prescriber if she is pregnant or breastfeeding.
• Tell patient he'll undergo regular blood testing during therapy.
• As appropriate, review all other significant and life-threatening adverse reactions and interactions, especially those related to the drugs and tests mentioned above.
- Urinary tract infections,
- Pulmonary infections.
Time/action profile (antifungal blood levels)
|PO||rapid||1–2 hr||6 hr|
Adverse Reactions/Side Effects
Central nervous system
- seizures (life-threatening)
- chest pain
Ear, Eye, Nose, Throat
- hearing loss
- diarrhea (most frequent)
- nausea (most frequent)
- vomiting (most frequent)
- abdominal pain
- dry mouth
Fluid and Electrolyte
- aplastic anemia (life-threatening)
- leukopenia (most frequent)
- pancytopenia (most frequent)
- peripheral neuropathy
Drug-Drug interactionAdditive bone marrow depression with other bone marrow depressant drugs, including antineoplastics and radiation therapy.Amphotericin B may ↑ toxicity of flucytosine but may also increase its antifungal activity.Cytarabine may ↓ its antifungal activity.
Renal ImpairmentOral (Adults) CCr 20–40 mL/min—12.5 mg/kg every 12 hr; CCr 10–20 mL/min—12.5 mg/kg every 24 hr; CCr <10 mL/min—12.5 mg/kg every 24–48 hr.
Availability (generic available)
- Assess patient for signs and symptoms of systemic fungal infection prior to and periodically throughout therapy.
- Obtain specimens for culture prior to initiating therapy. First dose may be given before receiving results.
- Lab Test Considerations: Monitor AST, ALT, serum bilirubin, and alkaline phosphatase prior to and frequently during therapy.
- Monitor BUN and serum creatinine prior to and periodically during therapy. Dose should be reduced in renal impairment. Monitor serum flucytosine concentrations in patients with renal impairment to prevent accumulation. Side effects are more common with serum concentrations >100 mcg/mL.
Therapeutic peak serum flucytosine levels range from 25–100 mcg/mL. Peak levels should be obtained 2 hours after a dose.
- Monitor hematologic function periodically during therapy. May cause anemia, leukopenia, or thrombocytopenia.
Potential Nursing DiagnosesRisk for infection (Indications)
Risk for deficient fluid volume (Adverse Reactions)
Deficient knowledge, related to medication regimen (Patient/Family Teaching)
- The number 5 in 5-FC is part of the drug name and not the dose.
- Oral: To reduce nausea and vomiting, administer capsules a few at a time over 15 min.
- Advise patient to take medication as directed, even if feeling better. Missed doses should be taken as soon as remembered, if not almost time for next dose; do not double doses.
- May cause dizziness or drowsiness. Caution patient to avoid driving and other activities requiring alertness until response to medication is known.
- Caution patient to use sunscreen and wear protective clothing to prevent photosensitivity reactions.
- Instruct patient to notify health care professional promptly if rash, fever, sore throat, yellowing of skin or eyes, changes in color of stool or urine, diarrhea, unusual bleeding or bruising, unusual tiredness, or weakness occurs.
- Emphasize the importance of follow-up exams to determine effectiveness of treatment.
- Instruct patient to notify health care professional immediately if planning to become pregnant.
- Resolution of the signs and symptoms of fungal infection. Duration of therapy is generally 4–6 wk but may continue for several months.