(for veterinary information only)
To remove parasites from the body, the biological differences between worm and mammal are exploited. In the case of members of the roundworm family (the "ascarid" worms), the parasitic worm is attached to the host’s intestine by its tiny teeth and/or suckers. Pyrantel acts as a neuromuscular blocker so that the parasite relaxes its grip, effectively paralyzing the worm so that it loses its attachment. The worm is then passed with the feces into the cold, cruel world. Outside of the host protective body, the worm soon dies. Because the medication is absorbed poorly from the host’s intestine, the host is completely unaffected by the paralysis effect. It also helps that the host is substantially larger than the parasite thus the small amounts of medication needed to remove parasites are not of concern to the mammal host.
Pyrantel pamoate is effective against numerous parasitic worms:
Pyrantel pamoate is also used in horses, cattle, sheep, pigs and many other species. When a new puppy or kitten is adopted and has been said to have been “dewormed” the chances are it is this product that was used. Pyrantel pamoate is not effective against whipworms nor is it effective against tapeworms. Larval roundworms and hookworms migrate through the host's body before completing their development in the host's intestine. Only the worms in the intestine are vulnerable to pyrantel pamoate. In order to address the worms in the process of migration, the deworming must be repeated after these worms have had the opportunity to reach the intestine. This means that there must be a second deworming 2-4 weeks after the first deworming and possibly even a third deworming 2-4 weeks after that.
Worms are frequently passed with some diarrhea, straining, and sometimes vomiting. An extremely heavily parasitized very small animal may suffer a worm impaction when a large number of worms die and try to pass at the same time. This is a very unusual possibility but one should be aware of it if one is using pyrantel pamoate in very small animals. The CDC recommends deworming as young as age 2 weeks for dogs and cats.
It is recommended that the following drugs not be used with pyrantel pamoate as they increase side effects potential: levamisole, morantel, or piperazine (all are other dewormers) or with organophosphate insecticides.
Pyrantel pamoate is safe to use in pregnancy and lactation and is frequently used in these situations to minimize the worm burdens of neonatal animals.
Page last updated: 5/27/2013
Page last reviewed: 7/12/2014