Ivermectin binds selectively and with high affinity to glutamate-gated chloride channels present in nerve and muscle cells of invertebrates. Increased chloride influx hyperpolarizes the cell membrane, leading to flaccid paralysis and death of susceptible parasites. It also potentiates GABA-mediated transmission in nematodes, further inhibiting neuromuscular activity, while its limited penetration of the mammalian blood-brain barrier protects humans from similar effects.