Pharmacokinetics of Orally Administered Fluralaner in Alpacas (Vicugna pacos) Affected by Sarcoptic Mange

Sarcoptic mange may cause severe clinical disease in alpacas (Vicugna pacos), and treatment outcomes with commonly used acaricides can be variable. Fluralaner, an isoxazoline drug licensed as an insecticide and acaricide in different species, has been reported as a promising off-label option in alpacas, but pharmacokinetic data and evidence from herd settings are lacking. This study aims to define the pharmacokinetic profile of orally administered fluralaner in alpacas naturally affected by sarcoptic mange. A herd of seven adult female alpacas with clinical mange received a single oral dose of fluralaner at 5.2 mg/kg. Serial blood sampling from pre-treatment to 60 days post-administration was performed; then, serum fluralaner concentrations were quantified by a validated UPLC–HRMS-MS/MS method and analyzed using a non-compartmental approach for pharmacokinetic profile determination. Fluralaner showed prolonged systemic exposure, although marked inter-individual variability was observed. Mean Cmax was 498.18 ± 302.02 ng/mL, reached at 1.6 ± 0.5 days, with an AUClast of 3323.19 ± 1866.60 ng × day/mL and an elimination half-life of 6.8 ± 2.8 days. Quantifiable concentrations persisted for 35.0 ± 11.2 days on average. No adverse effects were observed, and all animals showed progressive clinical improvement. The findings indicate that a single oral dose of fluralaner provides sustained systemic exposure in alpacas, while further studies are warranted to refine the dosing regimen and to assess its clinical efficacy under herd conditions.