QUEST PLUS Equine Oral Gel contains two active pharmaceutical ingredients, moxidectin and praziquantel. Moxidectin acts by interfering with chloride channel-mediated neurotransmission in the parasite. This results in paralysis and elimination of the parasite. Moxidectin is safe for use in horses and ponies because it does not have the same injurious effect on the mammalian nervous system. Praziquantel increases the tapeworm’s membrane permeability to calcium and other cations causing severe contraction and paralysis of the tapeworm’s muscles. This spastic paralysis results in the inability of tapeworms to attach to the host’s intestinal wall. Detached tapeworms are either destroyed by the host’s immune defense system or passed in the feces.