The study objective was to determine the pharmacokinetics and clinical effects of an extended-release 5% eprinomectin formulation (Longrange® ) following subcutaneous (s.c.) injection in healthy (n = 6) and mange-infected (n = 4) adult alpacas. High-performance liquid chromatography was used to analyze plasma samples obtained at regular intervals for 161 days following a single 5 mg/kg injection s.c. in healthy alpacas, and for 5 days following each dose (3 treatments, 2 months apart) in mange-affected animals. Skin scrapings and biopsies were performed pre- and post-treatment at two comparable sites in alpacas with mange. Four alpacas served as healthy controls. Eprinomectin plasma concentrations showed a biphasic peak (CMAX -1: 5.72 ± 3.25 ng/mL; CMAX -2: 6.06 ± 2.47 ng/mL) in all animals at 3.88 ± 5.16 days and 77 ± 12.52 days, respectively. Eprinomectin plasma concentrations remained above 1.27 ± 0.96 ng/mL for up to 120 days. Hematocrit (35.8 vs. 31.3%, P < 0.003) and albumin (3.5 vs. 2.8 g/dL P < 0.006) reduced significantly over 6 months in multidose animals, while fecal egg counts did not differ between groups. Self-limiting injection site reactions occurred in 9 of 10 animals. Pre- and post-treatment skin biopsies showed reduced hyperkeratosis, but increased fibrosis, with 1 of 4 alpacas remaining positive on skin scraping for mange. In conclusion, alpacas require a higher eprinomectin dose (5.0 mg/kg s.c.) than cattle, to reach comparable plasma concentrations.
© 2016 John Wiley & Sons Ltd.