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Find information on animal health topics, written for the veterinary professional.

Tetrahydropyrimidines

By Jozef Vercruysse, DVM, Professor, Faculty of Veterinary Medicine, Ghent University ; Edwin Claerebout, DVM, PhD, DEVPC, Professor, Department of Virology, Parasitology and Immunology, Faculty of Veterinary Medicine, Ghent University

Pyrantel was first introduced as a broad-spectrum anthelmintic against GI nematodes of sheep and has also been used in cattle, horses, dogs, cats, and pigs. It is available as a citrate, tartrate, embonate, or pamoate salt.

Aqueous solutions are subject to isomerization on exposure to light, with a resultant loss in potency; therefore, suspensions should be kept out of direct sunlight. It is not recommended for use in severely debilitated animals because of its levamisole-type pharmacologic action.

Pyrantel is used PO as a suspension, paste, drench, or tablets. Both pyrantel and morantel are effective against adult gut worms and larval stages that dwell in the lumen or on the mucosal surface.

Ruminants:

Pyrantel tartrate is effective as a broad-spectrum anthelmintic in ruminants; however, its activity is mainly limited to the adult GI nematodes.

Horses:

Pyrantel is effective against adult ascarids, large and small strongyles, and pinworms. At double the recommended dose, it has limited activity against the ileocecal tapeworm Anoplocephala perfoliata.

Swine:

Pyrantel tartrate is used in swine to treat Ascaris and Oesophagostomum.

Dogs and Cats:

Pyrantel pamoate or embonate is effective against the common GI nematodes, except for whipworms. Oxantel, a phenol analogue of pyrantel, is combined with pyrantel in some anthelmintic preparations for dogs (and people) to increase activity against whipworms.