European Medicines Agency Veterinary Medicines and Inspections

1. Ivermectin belongs to the macrocyclic lactone class of endectocides and consists of a mixture of two homologous compounds, 22,23-dihydroavermectin B1a (H2B1a, not less than 80%) and 22,23-dihydroavermectin B1b (H2B1b, not more than 20%). Avermectins are potent anthelmintic, insecticidal and acaracidal compounds which, by increasing the membrane permeability to chloride ions, mediate the paralysis of the nematodes and certain classes of ectoparasites.