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1 June 2010 Pharmacokinetics of Terbinafine After Single Oral Dose Administration in Red-Tailed Hawks (Buteo jamaicensis)
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To determine pharmacokinetic parameters of orally administered terbinafine hydrochloride for potential treatment of aspergillosis in raptors, 10 adult red-tailed hawks (Buteo jamaicensis) were used in single dose trials by using 15, 30, and 60 mg/kg doses with a 2-week washout period between trials. After administration of 15 mg/kg terbinafine, mean (± SD) plasma concentration peaked in approximately 5 hours at 0.3 ± 0.24 µg/mL, whereas a 30 mg/kg dose resulted in peak mean (± SD) plasma concentration of 1.2 ± 0.40 µg/mL in 3 hours and a 60 mg/kg dose resulted in mean (± SD) concentration of 2.0 ± 0.75 µg/mL in 5 hours. The volume of distribution decreased with increasing doses, averaging 76.8 ± 38.06 mL/kg for the 15 mg/kg dose and falling to 55.2 ± 17.4 mL/kg for the 30 mg/kg dose. This suggests that terbinafine accumulated in deep tissues, limiting further distribution at higher doses. The harmonic mean (± SD) half-life was biphasic, with initial values of 14.7 ± 6.67 hours, 17.5 ± 8.7 hours, and 13.3 ± 5.03 hours for 15, 30, and 60 mg/kg doses, respectively. A rapid first-elimination phase was followed by a slower second phase, and final elimination was estimated to be 161 ± 78.2 and 147 ± 65.6 hours for 15 and 30 mg/kg doses, respectively. Linearity was demonstrated for the area under the curve but not for peak plasma concentrations for the 3 doses used. Calculations based on pharmacokinetic parameter values indicated that a dosage of 22 mg/kg terbinafine q24h would result in steady-state trough plasma concentrations above the minimum inhibitory concentration of terbinafine (0.8–1.6 µg/mL). This dosage is recommended as a potential treatment option for aspergillosis in raptors. However, additional research is required to determine both treatment efficacy and safety.

Ursula Bechert, J. Mark Christensen, Robert Poppenga, Sahar A. Fahmy, and Patrick Redig "Pharmacokinetics of Terbinafine After Single Oral Dose Administration in Red-Tailed Hawks (Buteo jamaicensis)," Journal of Avian Medicine and Surgery 24(2), 122-130, (1 June 2010).
Published: 1 June 2010

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