Kinetics and anthelmintic efficacy of topical eprinomectin when given orally to goats

- Topical eprinomectin in goat has reportedly an irregular anthelmintic efficacy.
- Kinetics and efficacy were determined for topical eprinometin given orally.
- Kinetics parameters indicated a higher drug availability for oral route.
- Anthelmintic efficacy was ≥99.8% with the oral route.
- Additional information is needed concerning food safety.

Preliminary data suggest that topical eprinomectin in goat shows an individual variation in anthelmintic efficacy when used off-license at a dose rate of 0.5 or 1.0 mg/kg BW. As a result, the use of oral administration of topical formulation of eprinomectin tends to develop in dairy goat farms in France. The plasma levels and milk excretion as well as the anthelmintic efficacy of eprinomectin were determined in goats following oral administration of a topical formulation of the drug at dose rates of 0.5 and 1 mg/kg BW. The area under the concentration-time curve (AUC) values were 17.62 ± 9.68 ng day/ml and 6.56 ± 4.00 ng day/ml for plasma and milk respectively after the administration of 0.5 mg/kg BW and 45.32 ± 13.90 ng day/ml and 13.88 ± 1.77 ng day/ml for plasma and milk, respectively after the administration of 1 mg/kg BW. The milk-to-plasma ratio ranged from 0.33 to 0.36 and the amount of drug recovered in the milk was 0.4% of the total administered dose. The maximum concentrations of eprinomectin residues determined in milk after oral treatment were <20 μg/kg (Maximum Residue Limit in goat milk). The anthelmintic efficacy of the oral administration of topical eprinomectin was 100% through Faecal Egg Count Reduction Test in natural infection and ≥99.8% through Controlled Test in experimental infection (Haemonchus contortus and Trichostrongylus colubriformis). Additional information is needed about the fate of the vehicles used for topical formulation when given by oral route concerning food safety.