Ivermectin is a member of the macrocyclic lactone class of endectocides, which have a high affinity to glutamate-gated chloride ion channels found in invertebrate nerve and muscle cells. Ivermectin increases permeability of the cell membrane to chloride ions with hyperpolarization of the nerve or muscle cell, resulting in paralysis and death of the parasite. Compounds of this class may also interact with other ligand-gated chloride channels, such as those gated by the neurotransmitter gamma-amino butyric acid (GABA).
Ivermectin is highly safe to mammals, as they do not possess glutamate-gated chloride channels. Macrocyclic lactones have a low affinity for other mammalian ligand-gated chloride channels and they do not readily cross the blood-brain barrier.