Pyrantel

Pyrantel is a tetrahydropyrimidine anthelmintic used mainly against intestinal nematodes. Pamoate and tartrate products differ in solubility and clinical formulation. Veterinary applications include roundworms and hookworms in companion animals and selected equine or livestock nematodes. Some equine regimens also target susceptible ileocecal tapeworms.

Group

Tetrahydropyrimidine anthelmintic

Mechanism of Action

Pyrantel activates nicotinic acetylcholine receptors at susceptible nematode neuromuscular junctions. Persistent depolarization produces spastic paralysis, preventing the worms from maintaining their position in the intestinal lumen. Normal intestinal movement then assists expulsion. Limited absorption of some formulations concentrates activity within the gut. Anthelmintic activity depends on parasite species and exposure.

Dose Rates

Dogs

Use / stage	Dose	Route	Schedule	Instructions
Intestinal nematodes	5 mg/kg	PO	Once	Repeat after 7-10 days.
Intestinal nematodes in small dogs	10 mg/kg	PO	Once	Pyrantel base; dogs below 5 lb. The original table does not define exactly 5 lb.
Puppy intestinal nematodes	5–10 mg/kg	PO	Once	From 2-3 weeks of age; reported repeat every 2-3 weeks to at least 12 weeks.

Cats

Use / stage	Dose	Route	Schedule	Instructions
Intestinal nematodes	20 mg/kg	PO	Once	May mix with food.

Horses

Use / stage	Dose	Route	Schedule	Instructions
Intestinal nematodes	6.6 mg/kg	PO	Once
Medicated-feed nematode treatment	12.5 mg/kg	PO	Once
Medicated-feed nematode prevention	2.6 mg/kg	PO	Every 24 h
Cestodes	13.2 mg/kg	PO	Once	Pyrantel base by mouth; reported once or twice yearly in parasite-control plans.

Pigs

Use / stage	Dose	Route	Schedule	Instructions
Intestinal nematodes	22 mg/kg	PO	Once	Administer in feed.

Indications

Treatment of susceptible roundworm and hookworm infections in dogs and cats.
Treatment of susceptible equine ascarids, strongyles and pinworms with an appropriate formulation.
Treatment of selected equine Anoplocephala perfoliata infection using a supported cestocidal regimen.
Treatment or control of selected intestinal nematodes in pigs or other veterinary species with an indicated product.

Interactions

Potential increased CNS toxicity with levamisole.

Adverse effects

Generally well tolerated at routine doses.

Toxicity

Marked exposure may produce tachypnea, sweating, ataxia and other cholinergic signs; toxic potential differs between pamoate and tartrate salts.

Preparations

Preparation	Form	Strength	Route
Pyrantel suspension 2.27 mg base/mL	Oral Liquid	2.27 mg / mL	PO
Pyrantel suspension 4.54 mg base/mL	Oral Liquid	4.54 mg / mL	PO
Pyrantel suspension 50 mg base/mL	Oral Liquid	50 mg / mL	PO
Pyrantel tablet 22.7 mg base	Tablet	22.7 mg / tablet	PO
Pyrantel tablet 113.5 mg base	Tablet	113.5 mg / tablet	PO

Monitoring and Administration

Dose as pyrantel base. Shake suspensions and monitor fecal parasite response. Protect from freezing; parasite-control schedules may require repeat treatment.

Equine cestode amount is 13.2 mg/kg; the administration route is unspecified for this regimen and no route-specific calculator regimen is created.

Many pamoate amounts in the older reference do not identify salt versus base. Do not reassign those to the base calculator. Rabbit pinworm line reads 15-10 mg/kg, a reversed/ambiguous range. Pig tartrate 22 mg/kg single or 2.6 mg/kg/day for 3 days, ruminant tartrate 25 mg/kg, bird pamoate and feline combination amounts need their exact ingredient basis before normalization.