Tolfenpyrad is a pyrazole insecticide, and was discovered by Mitsubishi Chemical Corporation in 1991. The compound acts mainly through the inhibition of the mitochondrial electron transport system. Tolfenpyrad has shown activity against parasitic larval stages (xL3 and L4) of H. contortus in vitro; IC50 values were comparable with those of two commercially available anthelmintics, monepantel and moxidectin. As a pesticide, tolfenpyrad has relatively broad activity against egg, larval, nymphal and adult stages of various arthropods (including Hemiptera, Coleoptera, Diptera, Lepidoptera, Thysanoptera and Acarina), and has been applied to various infested crops. This chemical was developed in Japan and was first approved in 2002; it has been registered for commercial use in several countries other than Japan, including the Dominican Republic, Thailand, the United Arab Emirates, Indonesia and the USA.