Pyrantel pamoate ( CAS: 22204-24-6)

Pyrantel pamoate is used as a deworming agent in the

treatment ofhookworms (all species) and roundworms (Ascaris lumbricoides,

aka ascarids in humans) in domesticated animals such as horses, cattle, sheep,

pigs, cats, dogs, and many other species. It is a combination of pyrantel and

pamoic acid. 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.

It is also used for pinworm treatment for humans in many brands, including “

Reese’s Pinworm Medicine”, “Pin-X”, “Pin-Rid”,”PYRANTRIN” formally called

“COMBANTRIN”, “Anthel”, “Helmintox”, “Helmex”.

Pyrantel pamoate is also commonly included in monthly administered chewable

heartworm preventative tablets for dogs.

Drug action

Pyrantel pamoate acts as a depolarizing neuromuscular blocking agent, thereby

causing sudden contraction, followed by paralysis, of the helminths. This has the

result of causing the worm to “lose its grip” on the intestinal wall and be passed

out of the system by natural process. Since Pyrantel is poorly absorbed by the host’s

intestine, the host is unaffected by the small dosage of medication used. 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.

Toxicity

Pyrantel pamoate is considered a Pregnancy category C drug for use during pregnancy for

humans, but is in category A for canines and felines. Pyrantel is considered safe to use in

nursing animals.