The pharmacokinetics of eprinomectin ERl (LongRrange®, Merial) administration under the skin in healthy and mange-affected alpacas

Principal Investigator:

John M. Pollock, DVM
Tufts Cummings School of Veterinary Medicine
Woodstock, Connecticut

Objective: The goal of this study is to determine the pharmacokinetics (drug uptake, distribution and elimination) of a long-acting dewormer, eprinomectin.

Procedures: Fourteen alpacas were randomly assigned to an eprinomectin-treatment (6 healthy animals and 4 mange-affected alpacas) and a control group (4 animals). Alpacas in the healthy treatment group received a single injection of 5mg/kg eprinomectin (5%) under the skin, while mange-affected alpaca were treated repeatedly at two month intervals. Sequential physical examinations and blood analyses were performed at designated time points following each drug injection, to determine plasma eprinomectin levels and potential drug side-effects.

Clinical Relevance: LongRange® is a new, long-acting injectable dewormer which could be useful for the treatment of mange and prevention of meningeal worm infection in alpacas. However, LongRange® needs to be specifically evaluated in alpacas to optimize its use, minimize its misuse, and counteract development of resistance.

Results and Conclusions: Eprinomectin plasma concentrations remained above 1.27±0.96 ng/mL for up to 120 days after a single injection. Repeated use resulted in some decreases in red cell and blood protein concentrations, while fecal-egg-counts did not differ between treated and untreated groups. Self-limiting injection-site reactions occurred in 9/10 animals. Skin biopsies and scrapings performed before and after 6 months of treatment in mange-affected animals showed less skin thickening (hyperkeratosis) but increased scarring (fibrosis), with 1 of 4 animals remaining positive on skin scraping for mange. In conclusion, alpacas require a higher eprinomectin dose (5mg/kg given under the skin) than cattle, to reach comparable drug concentrations in their bloodstream.