Pharmacokinetics and anthelmintic efficacy of topical eprinomectin in goats prevented from grooming.

Pharmacokinetics and anthelmintic activity of topical eprinomectin in goats prevented from physical contact to others and self-grooming were studied. Sixteen approximately 7 months old male castrated German White Noble goats harbouring induced infections of gastrointestinal nematode parasites were included in the study. They were blocked based on pre-treatment body weight (range 22.4 to 36.4 kg) and then randomly allocated to the untreated control group or the group treated with topical 0.5% w/v eprinomectin (EPRINEX Pour-on, Merial) at 1 mg/kg body weight. Plasma samples were collected prior to and at intervals up to 14 days following treatment and analyzed to determine the concentrations of eprinomectin (B1a component). Parasites were recovered, identified, and counted following necropsy 14 days after treatment. Goats treated with topical eprinomectin had significantly fewer (≥99% reduction, p < 0.01) adult Cooperia curticei, Haemonchus contortus, Nematodirus battus, Oesophagostomum venulosum, Ostertagia circumcincta, and Trichostrongylus colubriformis than the untreated controls. Basic pharmacokinetic parameters for eprinomectin B1a were AUCinfinity, 37.1 ± 15.2 day ng/mL; T½, 5.11 ± 2.83 days; and Cmax, 5.93 ± 1.87 ng/mL; individual maximal concentrations were observed 1 or 2 days after treatment. Results of this study indicate that oral ingestion is not required to achieve adequate exposure for excellent anthelmintic efficacy following topical administration of eprinomectin at 1 mg/kg body weight to goats.