Drugs that expel or kill parasitic worms in a host
Explanation
Anthelmintics are pharmaceuticals used to treat infections by parasitic worms, including nematodes, cestodes and trematodes. To be effective, these agents must be selectively toxic to the parasite while sparing the host’s tissues. The MSD Veterinary Manual notes that anthelmintic drugs achieve this selective toxicity by inhibiting biochemical processes vital to the parasite or by interfering with neuromuscular coordination【100806267192512†L95-L99】. Disruption of parasite cell integrity, paralysis or interference with protective mechanisms leads to starvation, death and expulsion of the worm from the gastrointestinal tract or other tissues【100806267192512†L110-L118】. Common classes include benzimidazoles, which bind β‑tubulin and prevent microtubule polymerization; macrocyclic lactones that increase chloride permeability causing flaccid paralysis; nicotinic agonists such as levamisole and pyrantel that cause spastic paralysis; and isoquinolones like praziquantel that disrupt calcium homeostasis. These drugs are used in both human and veterinary medicine to control ascariasis, hookworm, tapeworms, schistosomiasis and a variety of animal helminths. Mass drug administration programs use albendazole or ivermectin to combat neglected tropical diseases such as lymphatic filariasis and onchocerciasis.
Mechanisms and examples
Specific anthelmintics exploit differences between host and parasite physiology. Benzimidazoles (e.g., albendazole, mebendazole) inhibit parasite microtubule formation and deplete glycogen stores. Ivermectin and other macrocyclic lactones open glutamate‑gated chloride channels, causing paralysis. Nicotinic agonists such as pyrantel and levamisole activate acetylcholine receptors, leading to sustained contraction and expulsion. Praziquantel increases membrane permeability to calcium, causing tetanic contraction and tegumental damage. Newer agents target energy metabolism by uncoupling oxidative phosphorylation or inhibiting glycolytic enzymes【100806267192512†L125-L134】. In livestock, misuse and underdosing have led to widespread resistance, prompting integrated parasite management practices.
Anthelmintics remain critical for human and animal health. Continued surveillance for resistance and rational drug use are essential to preserve their efficacy and protect populations in endemic areas.
Related Terms: Anthelmintic Resistance, Antiparasitic, Antiprotozoal, Antimicrobials, Helminths