Flucytosine: Uses, Interactions and Safety
Uses
Flucytosine is an antifungal for serious infections, especially cryptococcosis and systemic candidiasis. It is usually combined with another antifungal, commonly amphotericin B, because resistance can develop rapidly with flucytosine alone. Turkish infectious-disease teaching material includes it in cryptococcal induction treatment.
Administration
This summary focuses on oral capsules and tablets. Intravenous products exist in some countries and have separate instructions. Kidney function strongly influences flucytosine exposure, so the clinical team sets the regimen and adjusts it when needed. Blood counts, liver tests, kidney function and sometimes drug concentrations are checked during treatment.
Safety
Too much flucytosine can cause severe bone-marrow and liver toxicity. Tell the team about kidney disease, blood disorders and known dihydropyrimidine dehydrogenase deficiency. Complete DPD deficiency is contraindicated in the US capsule label; the WHO tablet information prohibits known DPD deficiency. Fever, mouth sores, unexpected bruising, bleeding, severe diarrhoea, jaundice or reduced urine output need prompt assessment.
Interactions
Medicines that suppress blood-cell production or reduce kidney filtration may increase toxicity. Ciclosporin and tacrolimus require particular monitoring. Phenytoin concentrations may increase through a potential interaction involving the fluorouracil metabolite. Certain DPD inhibitors and fluorouracil products are prohibited combinations. Necessary antifungal combination treatment is not itself a reason to stop therapy.
Pregnancy and breastfeeding
Pregnancy requires specialist assessment and is generally avoided unless a life-threatening infection leaves no effective alternative. The WHO information specifies contraception precautions for women and men. Breastfeeding is generally avoided because serious infant effects cannot be excluded.
Adverse effects
Gastrointestinal symptoms, reduced white-cell or platelet counts and increased liver enzymes are recognised adverse effects. Frequency estimates from a specific tablet product should not be assumed for every formulation. A current Turkish product authorisation or supply route was not established by the Turkish medical-society source.
Sources
The linked Turkish profile contains the medicine record and its documented interaction list.