플루시토신

항진균제

**플루시토신**(5-FC)은 주로 **크립토코쿠스(Cryptococcus)** 및 **칸디다(Candida)** 균주에 활성을 나타내는 불소화 피리미딘계 항진균제입니다. **주요 임상 포인트:** * **병용 요법 필수:** 단독 요법으로 사용 시 진균의 내성이 매우 빠르게 발현됩니다(특히 크립토코쿠스). 따라서 거의 항상 **암포테리신 B(Amphotericin B)** 또는 아졸계 항진균제와 시너지 효과를 위해 병용 투여됩니다. * **중추신경계 침투:** 혈액-뇌 장벽(BBB)을 매우 잘 통과하므로 중추신경계 크립토코쿠스증 치료에 매우 유용합니다. * **독성 우려:** 용량 의존적인 골수 억제 위험이 있습니다. 개는 특히 민감하여 10-14일 이상 치료 시 심각한 약물 부작용이 발생할 수 있습니다. * **종간 차이:** 포유류 세포는 일반적으로 플루시토신을 독성 대사산물(5-플루오로우라실)로 변환하는 효소가 부족하지만, 장내 세균총이나 특정 종의 대사(예: 랫트)로 인해 전신 독성이 발생할 수 있습니다.

작용 기전: Flucytosine acts as a prodrug that exploits specific fungal enzymes: 1. **Cellular Entry:** Flucytosine enters the fungal cell via the enzyme **cytosine permease**. 2. **Conversion to Active Metabolite:** Inside the fungal cell, it is deaminated by **cytosine deaminase** → **5-fluorouracil (5-FU)**. *(Note: Human and most mammalian cells lack this enzyme, providing selective toxicity).* 3. **RNA Inhibition:** 5-FU acts as an antimetabolite, competing with **uracil** → incorporates into fungal RNA → disrupts pyrimidine metabolism and halts protein synthesis. 4. **DNA Inhibition:** 5-FU is also converted to **fluorodeoxyuridylic acid** → potently inhibits **thymidylate synthetase** → halts DNA synthesis and cell division.

동물 종별 용량

Cats

Cryptococcosis · 30 mg/kg PO q6h or 50 mg/kg PO q8h or 75 mg/kg PO q12h · PO · q6h, q8h, or q12h · 1-9 months · Cats 3.5 kg or greater should receive 250 mg (total) q6-8h. Must be given with a polyene (amphotericin B) or azole antifungal agent.
Candidiasis · 25-50 mg/kg PO q6h or 50-65 mg/kg PO q8h · PO · q6h or q8h · 42 days · Must be given with a polyene or azole antifungal agent.

Birds

Susceptible fungal infections (Psittacines) · 250 mg/kg twice daily as a gavage · PO · q12h · Extended periods · May cause bone marrow toxicity; periodic hematologic assessment is recommended.
Susceptible fungal infections (Raptors) · 18-30 mg/kg q6h as a gavage · PO · q6h
Susceptible fungal infections (Psittacines and Mynahs) · 100-250 mg/lb in feed · PO · Continuous · For flock treatment of severe aspergillosis or Candida. Apply to favorite food mix or mixed with mash.
Susceptible fungal infections (Ratites) · 80-100 mg/kg PO twice daily · PO · q12h

Dogs

Cryptococcosis · 50-75 mg/kg PO q8h · PO · q8h · 1-12 months · Must be given with a polyene or azole antifungal agent.
Candidiasis · 25-50 mg/kg PO q6h or 50-65 mg/kg PO q8h · PO · q6h or q8h · 42 days · Must be given with a polyene or azole antifungal agent.

용량은 면허 수의 전문가를 위한 임상 참고 자료입니다. 항상 최신 라벨과 개별 환자에 대해 확인하십시오.

투여 경로

금기

Known hypersensitivity to flucytosine

이상반응

Gastrointestinal disturbances (nausea, vomiting, diarrhea)
Dose-dependent bone marrow depression (anemia, leukopenia, thrombocytopenia)
Cutaneous eruption and rash (primarily on scrotum and nasal planum in dogs)
Oral ulceration
Increased hepatic enzymes
Severe drug reaction in dogs within 10-14 days of treatment
Aberrant behavior and seizures (reported in cats)
Toxic epidermal necrolysis (anecdotal in cats)

약물 상호작용

Amphotericin B · Synergistic antifungal efficacy against Cryptococcus and Candida. However, amphotericin B-induced nephrotoxicity can decrease flucytosine excretion, leading to flucytosine accumulation and enhanced bone marrow toxicity. Dosage adjustments and strict monitoring are required.

모니터링

Renal function (BUN, Creatinine, Urinalysis) - at least twice weekly if also receiving amphotericin B
CBC with platelets (to monitor for bone marrow suppression)
Hepatic enzymes (at least monthly)
Serum flucytosine levels (target < 100 mcg/mL) in patients with renal impairment, if available

과용량

Specific information regarding flucytosine overdosage in veterinary species is limited. **Management:** * For substantial acute overdoses, standard gastrointestinal decontamination (gut emptying, activated charcoal, and cathartic administration) is recommended unless contraindicated. * Monitor hematologic and renal parameters closely, providing supportive care as needed.

VetSheet 약물 레퍼런스는 면허 수의 전문가를 위한 임상 의사결정 보조 도구이며, 전문적 판단이나 제조사의 최신 라벨을 대신하지 않습니다.