Flucytosine is taken up by fungal organisms via the enzyme cytosine permease. Inside the fungal cell, flucytosine is rapidly converted to fluorouracil by the enzyme cytosine deaminase. Fluorouracil exerts its antifungal activity through the subsequent conversion into several active metabolites, which inhibit protein synthesis by being falsely incorporated into fungal RNA or interfere with the biosynthesis of fungal DNA through the inhibition of the enzyme thymidylate synthetase.

Used for serious infections caused by Candida and Cryptococcus, including:

• Candida: Septicemia, endocarditis, urinary tract infections, and some pulmonary infections.
• Cryptococcus: Meningitis and pulmonary infections.

50–150 mg/kg/day in divided doses every 6 hours.

Hematologic: Anemia, leukopenia, thrombocytopenia, agranulocytosis, aplastic anemia
Hepatic: Liver enzyme elevation, hepatitis, hepatic necrosis
GI: Nausea, vomiting, diarrhea, ulcers, GI hemorrhage
Neuro: Ataxia, hallucinations, neuropathy, seizures
Other: Rash, photosensitivity, respiratory issues, cardiac arrest, allergic reactions

Flucytosine Capsules are contraindicated in patients with a known hypersensitivity to the drug.

Flucytosine Capsules are contraindicated in patients with known complete dihydropyrimidine dehydrogenase (DPD) enzyme deficiency.

Renal Impairment: Can lead to drug accumulation; monitor kidney function closely.

Bone Marrow Suppression: Risk of irreversible aplasia; monitor hematologic function.

DPD Deficiency: Increased toxicity due to accumulation of 5-FU (e.g., mucositis, diarrhea, neutropenia).