Tissue Depletion Profile of Ivermectin in Rabbits

Abstract

Avermectins are largely used in different animal species. Ivermectin, the most popular avermectin, is used against a wide spectrum of endo and ectoparasites. Some mange mites are particularly sensitive to ivermectin. Notoedres cati var. cuniculi, the agent of rabbit mange, is particularly sensitive to ivermectin. Pharmacokinetic and residual studies of ivermectin in rabbits, however, are scarce. The objective of the present paper was to study the tissue residue profile of ivermectin (IVM) after subcutaneous (s.c.) administration of a 1% w/w solution. Sixteen young healthy male rabbits received 200 μg/kg of a 1% w/w ivermectin formulation subcutaneously. Groups of four treated animals were sacrificed at 10, 20, 30 and 40 days after injection. Samples of liver, fat, kidney and muscle tissue were obtained. IVM concentrations were determined by liquid chromatography with fluorescence detection after automatic solid phase extraction with SPE C18 cartridges. Ivermectin was detected after subcutaneous administration until 40 days. Muscle samples showed the lowest IVM concentrations throughout the study. The highest IVM concentrations at all sampling times were measured in liver and fat tissues. Nevertheless, IVM concentrations in all the tissues analyzed were below the accepted maximum residue limits recommended by the European Union at 20 days posttreatment.