Pharmacokinetics and preliminary safety of single-dose oral fluralaner at 10 and 25 mg/kg in healthy horses revealed no adverse reactions.

Abstract: To determine the safety and pharmacokinetics of a single dose of the oral ectoparasiticide fluralaner at 10 and 25 mg/kg in healthy horses. Unassigned: 12 clinically healthy university-owned horses, 9 to 17 years of age, were administered a single oral dose of fluralaner at 10 or 25 mg/kg. Physical examinations, neurological examinations, plasma samples, hematology and biochemistry panels, and skin biopsies were collected throughout the 84-day trial period. Fluralaner concentrations were measured in plasma and skin by liquid chromatography-tandem mass spectrometry, and pharmacokinetics were evaluated in plasma using a noncompartmental analysis. Unassigned: After oral administration at 10 or 25 mg/kg, fluralaner was detected in all horses. Fluralaner was detectable in plasma for a mean of 42 ± 16.6 or 30.3 ± 3.61 days at the 10- and 25-mg/kg doses, respectively. Pharmacokinetic results for 10- and 25-mg/kg doses, respectively, were a terminal half-life of 6.03 ± 3.87 or 3.02 ± 0.25 days, maximum concentration of 162.1 ± 21.6 or 403.3 ± 129.5 ng/mL, and time to maximal concentration of 0.42 ± 0.14 or 0.64 ± 0.29 days. Skin concentrations in horses administered 25 mg/kg peaked 1 day postadministration at a median of 2.30 μg/g (IQR, 1.31 to 8.23 μg/g) and remained detectable to day 84. No adverse effects of fluralaner were detected. Unassigned: Fluralaner is absorbed orally at 10 and 25 mg/kg in healthy horses and appears to be safe and well tolerated. Unassigned: Fluralaner's persistence in skin and plasma after oral administration has potential as a treatment for select ectoparasites in the horse, although further study is needed to determine the appropriate dose and dose interval.