Plasma disposition and faecal excretion of eprinomectin following subcutaneous administration in Saanen and Alpine goats

Abstract

Eprinomectin is extensively used in veterinary medicine, particularly in the treatment of internal and external parasites in livestock, including goats. The pharmacokinetic behavior of eprinomectin in plasma and faeces was studied after a single subcutaneous administration in two different goat breeds at a dose of 0.2 mg/kg body weight. The study was conducted on one-year-old female Saanen (n = 8) and Alpine (n = 8) goats in a parallel design. There were no significant differences between Saanen and Alpine goats on the peak plasma concentration (Cmax, 28.59 ± 7.46 ng/mL vs. 37.69 ± 14.89 ng/mL), area under the curve (AUC0-∞, 93.08 ± 11.66 ng.d/mL vs. 116.98 ± 48.36 ng.d/mL), area under the first moment curve (AUMC0-∞, 311.05 ± 67.23 ng.d2/mL vs. 348.25 ± 202.64 ng.d2/mL) and mean residence time (MRT, 3.24 ± 0.77 d vs. 2.74 ± 0.64 d) values. The plasma terminal half-life and the time to reach peak plasma concentration were significantly higher in Saanen goats (T1/2λz, 2.18 ± 0.43 d; Tmax, 1.21 ± 0.25 d) than in Alpine goats (T1/2λz, 1.66 ± 0.41 d; Tmax, 0.79 ± 0.25 d). The results revealed that the plasma concentration of eprinomectin did not differ depending on the breed in Saanen and Alpine goats. However, it was determined that the eprinomectin clearance from the body may vary depending on the breed in goats. The faecal eprinomectin concentration of Saanen and Alpine goats was 90 and 80 times higher than the plasma eprinomectin concentration, respectively. Although high faecal excretion of eprinomectin confers a high efficacy advantage against parasites in the gastrointestinal tract, it may pose an ecotoxicological risk to manure fauna and aquatic organisms with high susceptibility to this compound.