Derquantel , a spirocyclic anthelmintic, is a competitive, orally active nicotinic acetylcholine receptor (nAChR) antagonist. Derquantel inhibits ACh-induced depolarization with an IC50 of 0.22 μM. By selectively antagonizing nAChRs on the somatic muscles of nematodes, Derquantel causes flaccid paralysis of muscles, thereby dislodging parasites from the host's gastrointestinal tract. Derquantel is applicable to research related to Haemonchus contortus infection and Ascaris suum infection.