Doses - FLUCYTOSINE

Dogs:

For cryptococcosis:
a) 25 - 50 mg/kg qid PO for a minimum of 6 weeks; with amphotericin B (0.5 mg/kg IV 3 times weekly for a minimum of 4-5 weeks until a cumulative dose of 4 mg/kg attained¯see amphotericin B monograph for more information). (Noxon 1989)
b) Flucytosine 150 - 175 mg/kg PO divided tid-qid with amphotericin B 0.15 - 0.4 mg/kg IV 3 times a week. When a total dose of amphotericin B reaches 4 - 6 mg/kg start maintenance dosage of amphotericin B at 0.15 - 0.25 mg/kg IV once a month with flucytosine at dosage above or with ketoconazole at 10 mg/kg PO once daily or divided bid. (Greene, O'Neal, and Barsanti 1984)
For candiduria:
a) To treat aggressively: After correcting identifiable predisposing factors, alkalinize urine to pH of >7.5 with oral sodium bicarbonate. Then give flucytosine at 67 mg/kg PO q8h.
Reduce dose if patient has renal failure. (Polzin and Osborne 1985)

Cats:

For cryptococcosis:
a) As an alternate to ketoconazole therapy: Flucytosine 200 mg/kg/day PO divided q6hwith amphotericin B (0.25 mg/kg in 30 ml D5W given IV over 15 minutes q48h¯Seeamphotericin B monograph for more information.). Continue therapy for 3-4 weeksafter clinical signs have resolved and no organisms can be recovered. (Legendre 1989)
b) 25 - 50 mg/kg qid PO for a minimum of 4-6 weeks; with amphotericin B (0.25 mg/kg IV 3 times weekly for a minimum of 3-4 weeks¯see amphotericin B monograph formore information). (Noxon 1989)
c) Flucytosine 125 - 250 mg/day PO divided tid-qid with amphotericin B 0.15 - 0.4 mg/kg IV 3 times a week. When a total dose of amphotericin B reaches 4 - 6 mg/kg startmaintenance dosage of amphotericin B at 0.15 - 0.25 mg/kg IV once a month withflucytosine at dosage above or with ketoconazole at 10 mg/kg PO once daily or dividedbid. (Greene, O'Neal, and Barsanti 1984)

Birds:

For susceptible fungal infections:
a) In Psittacines: 250 mg/kg bid as a gavage. May be used for extended periods of timefor aspergillosis. May cause bone marrow toxicity; periodic hematologic assessment isrecommended.
In raptors: 18 - 30 mg/kg q6h as a gavage.
In Psittacines and Mynahs: 100 - 250 mg/lb in feed for flock treatment of severe aspergillosis or Candida (especially respiratory Candida). Apply to favorite food mix or mixed with mash. (Clubb 1986)
Monitoring Parameters -

1) Renal function (at least twice weekly if also receiving amphotericin B)

2) CBC with platelets

3) Hepatic enzymes at least monthly
Client Information - Clients should report any symptoms associated with hematologic toxicity (abnormal bleeding, bruising, etc.). Prolonged treatment times, as well as costs of medication and associated monitoring, require substantial client commitment.
Dosage Forms/Preparations/FDA Approval Status - Veterinary-Approved Products: None

Human-Approved Products:

Flucytosine 250 mg, 500 mg Capsules; Ancobon® (Roche); (Rx)