Flucytosine

DOSAGE AND ADMINISTRATION

The usual dosage of Flucytosine Capsules USP is 50 to 150 mg/kg/day administered in divided doses at 6-hour intervals. Nausea or vomiting may be reduced or avoided if the capsules are given a few at a time over a 15-minute period. If the BUN or the serum creatinine is elevated, or if there are other signs of renal impairment, the initial dose should be at the lower level (see WARNINGS ).

Flucytosine Capsules USP should be used in combination with amphotericin B for the treatment of systemic candidiasis and cryptococcosis because of the emergence of resistance to Flucytosine Capsules USP (See MICROBIOLOGY ).

ADVERSE REACTIONS

The adverse reactions which have occurred during treatment with Flucytosine Capsules USP are grouped according to organ system affected.

Cardiovascular:

Cardiac arrest, myocardial toxicity, ventricular dysfunction.

Respiratory:

Respiratory arrest, chest pain, dyspnea.

Dermatologic:

Rash, pruritus, urticaria, photosensitivity.

Gastrointestinal:

Nausea, emesis, abdominal pain, diarrhea, anorexia, dry mouth, duodenal ulcer, gastrointestinal hemorrhage, acute hepatic injury including hepatic necrosis with possible fatal outcome in debilitated patients, hepatic dysfunction, jaundice, ulcerative colitis, enterocolitis, bilirubin elevation, increased hepatic enzymes.

Genitourinary:

Azotemia, creatinine and BUN elevation, crystalluria, renal failure.

Hematologic:

Anemia, agranulocytosis, aplastic anemia, eosinophilia, leukopenia, pancytopenia, thrombocytopenia, and fatal cases of bone marrow aplasia.

Neurologic:

Ataxia, hearing loss, headache, paresthesia, parkinsonism, peripheral neuropathy, pyrexia, vertigo, sedation, convulsions.

Psychiatric:

Confusion, hallucinations, psychosis.

Miscellaneous:

WARNINGS

Flucytosine Capsules USP must be given with extreme caution to patients with impaired renal function. Since Flucytosine Capsules USP is excreted primarily by the kidneys, renal impairment may lead to accumulation of the drug. Flucytosine Capsules USP serum concentrations should be monitored to determine the adequacy of renal excretion in such patients.

Dosage adjustments should be made in patients with renal insufficiency to prevent progressive accumulation of active drug. Flucytosine Capsules USP must be given with extreme caution to patients with bone marrow depression. Patients may be more prone to depression of bone marrow function if they: 1) have a hematologic disease, 2) are being treated with radiation or drugs which depress bone marrow, or 3) have a history of treatment with such drugs or radiation.

Bone marrow toxicity can be irreversible and may lead to death in immunosuppressed patients. Frequent monitoring of hepatic function and of the hematopoietic system is indicated during therapy. 5-Fluorouracil is a metabolite of flucytosine.

Dihydropyrimidine dehydrogenase is a key enzyme involved in the metabolism and elimination of 5-fluorouracil. Therefore, the risk of severe drug toxicity is increased when Flucytosine Capsules, USP is used in individuals with deficiency in DPD.

Possible drug toxicities include mucositis, diarrhea, neutropenia, and neurotoxicity. Determination of DPD activity may be considered where drug toxicity is confirmed or suspected. In the event of suspected drug toxicity, consider stopping Flucytosine Capsules USP, treatment.

CONTRAINDICATIONS

Flucytosine Capsules, USP is contraindicated in patients with a known hypersensitivity to the drug. Flucytosine Capsules, USP is contraindicated in patients with known complete dihydropyrimidine dehydrogenase (DPD) enzyme deficiency (see WARNINGS ).