Measurement of ivermectin concentrations in target worms and host gastrointestinal tissues: Influence of the route of administration on the activity against resistant Haemonchus contortus in lambs

► The anthelmintic action depends on the ability of the active drug to reach parasites. ► Ivermectin reaches the parasites from the gastrointestinal contents or from plasma. ► Ivermectin concentrations were higher in the abomasal content after its ir treatment. ► Drug concentrations in Haemonchus spp were higher after the ir administration of ivermectin. ► This advantageous pattern of IVM profiles may be relevant against resistant parasites.