Pyrantel pamoate

Pyrantel pamoate is used as a deworming agent in the treatment of hookworms (all species) and roundworms (Parascaris equorum, aka ascarids in humans) in domesticated animals such as horses, cattle, sheep, pigs, cats, dogs, and many other species. Some drug companies pair pyrantel pamoate with praziquantel for tapeworms, and sometimes febantel for whipworms in order to provide more complete treatment for intestinal parasites in one dose.

Pyrantel pamoate is also commonly included in monthly administered chewable heartworm tablets for cats and dogs.

Drug Action

(Antiminth, Pin-Rid, Pin-X) (C11H14N2S.C23H16O6) Depolarizes ganglionic block of nicotinic neuromuscular transmission on the cholinergic receptors of the nematode resulting in spastic paralysis of the worm. This has the result of causing the worm to "loose it's grip" on the intestinal wall and be passed out of the system by natural process. Since Pyrantel is poorly absorbed by the hosts intestine, the small dosage of medication used is completely ineffective to the host. Spastic (tetanic) paralyzing agents, in particular pyrantel pamoate, may induce complete intestinal obstruction in a heavy worm load. This obstruction is usually in the form of a worm impaction and happens when a very small, but heavily parasitized animal is treated and tries to pass a large number of dislodged worms at once. Worms usually pass in normal stool or with diarrhea, straining, and occasional vomiting. Dosage is 11 mg/kg not to exceed 1 g as a single dose.