Home Drug Guide Flucytosine

Drug Guide

Generic Name

Flucytosine

Brand Names Ancobon

Classification

Therapeutic: Antifungal agent

Pharmacological: Antimetabolite

FDA Approved Indications

Cryptococcal meningitis in conjunction with Amphotericin B
Maintenance therapy for cryptococcal meningitis after initial treatment

Mechanism of Action

Flucytosine is converted by fungal cells into 5-fluorouracil, which inhibits DNA and RNA synthesis, leading to fungal cell death.

Dosage and Administration

Adult: 25 mg/kg every 6 hours, adjusted based on renal function; typically used with Amphotericin B for cryptococcal meningitis.

Pediatric: Same as adult dosing, based on weight; dosage must be carefully adjusted for renal impairment.

Geriatric: Use with caution; renal function should be assessed.

Renal Impairment: Dose adjustment recommended based on renal function, as drug accumulation can occur.

Hepatic Impairment: No specific adjustment recommended, but monitoring advised.

Pharmacokinetics

Absorption: Well absorbed orally.

Distribution: Widely distributed in body tissues, including cerebrospinal fluid.

Metabolism: Minimal hepatic metabolism.

Excretion: Primarily excreted unchanged in urine.

Half Life: approximately 3-6 hours in patients with normal renal function.

Contraindications

Hypersensitivity to Flucytosine.

Precautions

Use with caution in patients with renal impairment, history of bone marrow suppression, or hepatic dysfunction.

Adverse Reactions - Common

Gastrointestinal disturbances (nausea, vomiting, diarrhea) (Common)
Bone marrow suppression (leukopenia, thrombocytopenia, anemia) (Common)

Adverse Reactions - Serious

Hepatotoxicity (Rare)
Orofacial or systemic hypersensitivity reactions (Rare)
Agranulocytosis (Rare)

Drug-Drug Interactions

Amphotericin B (enhanced myelosuppression)
Radiation therapy (increased bone marrow suppression)

Drug-Food Interactions

N/A

Drug-Herb Interactions

N/A

Nursing Implications

Assessment: Monitor renal function (BUN, serum creatinine), liver function tests, and complete blood counts regularly.

Diagnoses:

Risk for infection due to bone marrow suppression
Risk for injury related to hematologic abnormalities

Implementation: Administer with food to reduce gastrointestinal upset. Monitor for signs of toxicity and infection.

Evaluation: Evaluate blood counts, renal and hepatic function periodically to guide dosing and detect toxicities early.

Patient/Family Teaching

Report symptoms of rash, fever, sore throat, bleeding, or easy bruising immediately.
Adhere to scheduled lab tests for blood counts and liver/kidney function.
Use medication as prescribed—do not skip doses.
Maintain adequate hydration to assist renal excretion.

Special Considerations

Black Box Warnings:

Myelosuppression and hepatic toxicity are serious risks, especially with prolonged therapy.

Genetic Factors: No known significant genetic factors impacting use.

Lab Test Interference: Can cause false elevation of serum creatinine.

Overdose Management

Signs/Symptoms: Gastrointestinal symptoms, hematologic toxicity, hepatic dysfunction.

Treatment: Supportive care; monitor blood counts, renal and liver function; possibly use dialysis if indicated.

Storage and Handling

Storage: Store at room temperature, protected from light.

Stability: Stable under recommended conditions for shelf life specified by manufacturer.