Ivermectin binds selectively and with high affinity to glutamate-gated chloride ion channels found in nerve and muscle cells of parasites. This leads to an increase in the permeability of the cell membrane to chloride ions, causing hyperpolarization of the nerve or muscle cell, and resulting in paralysis and death of the parasite. Also they may interact with other ligand-gated chloride channels, such as those gated by the neurotransmitter gamma-aminobutyric acid (GABA).

Clorsulon kills adult Fasciola spp. by inhibition of enzymes in the glycolytic pathway, which is their primary source of energy.