Piperazine

Piperazine is an older nematode anthelmintic used principally against ascarids. Veterinary applications include roundworm treatment in dogs, cats, horses and selected livestock or poultry species, depending on the product. Its action paralyzes susceptible worms so they can be expelled from the intestine by normal gastrointestinal movement.

Group

Nematode anthelmintic

Mechanism of Action

Piperazine acts as an agonist at inhibitory GABA receptors on susceptible nematode muscle. Increased chloride conductance hyperpolarizes the muscle membrane and produces flaccid paralysis. Loss of normal muscle activity prevents the worm from maintaining its position in the intestine, allowing expulsion. This mechanism explains its relatively narrow practical spectrum, centered on susceptible ascarids.

Dose Rates

Dogs

Use / stage	Dose	Route	Schedule	Instructions
Ascarid infection	44–66 mg/kg	PO	Once
Ascarid infection	45–65 mg/kg	PO	Once	Piperazine base. Puppies under 2.5 kg have a 150-mg total ceiling; use that weight-qualified protocol separately.
Ascarid infection in small puppies	45–65 mg/kg	PO	Once	Maximum 150 mg/dose; Piperazine base; puppies under 2.5 kg only.

Cats

Use / stage	Dose	Route	Schedule	Instructions
Ascarid infection	44–66 mg/kg	PO	Once
Ascarid infection	45–65 mg/kg	PO	Once	Maximum 150 mg/dose; Piperazine base; repeat after 2-3 weeks may be required.

Horses

Use / stage	Dose	Route	Schedule	Instructions
Ascarid infection	110 mg/kg	PO		Give orally in drinking water as the sole water source; repeat schedule is unspecified.
Ascarid infection oral solution	Reference only	PO		Alternative product instruction: 30 mL of 17% solution per 45 kg orally; preserve product basis rather than equating an unspecified salt to base.
Ascarid infection	110 mg/kg	PO	Once	Explicitly piperazine base; repeat 3-4 weeks. Foal management may use later 10-week intervals.

Pigs

Use / stage	Dose	Route	Schedule	Instructions
Ascarid infection	110 mg/kg	PO		Give orally in drinking water as the sole water source; repeat schedule is unspecified.

Reptiles

Use / stage	Dose	Route	Schedule	Instructions
Nematodes	40–60 mg/kg	PO		Oral amount lacks confirmed salt/base basis; repeat after 2 weeks then fecal examination 14 days later.

Indications

Treatment of susceptible ascarid infections in dogs and cats, including Toxocara or Toxascaris species.
Treatment of susceptible equine Parascaris infections.
Treatment of selected ascarid infections in pigs or poultry using an indicated product.

Adverse effects

Ataxia, tremor and behavioral changes can occur.

Toxicity

Large piperazine exposure can produce weakness, ataxia, fasciculation, altered pupillary responses and respiratory paralysis. Support hydration, ventilation and neurologic status; signs may last several days.

Preparations

Preparation	Form	Strength	Route
Piperazine 50 mg	Tablet	50 mg / tablet	PO
Piperazine 250 mg	Tablet	250 mg / tablet	PO

Monitoring and Administration

Protect oral products from light and assess parasite control response.

Rabbit pinworm reports distinguish piperazine citrate 100 mg/kg orally daily for 2 days from adipate 200-500 mg/kg in adults or 750 mg/kg in young rabbits for 2 days. Rodent/rabbit water protocols use citrate 3 g/L for 2 weeks, or 2-5 mg/mL for 7 days followed by 7 days off and a repeated course. These salt-specific strengths are not equivalent to piperazine base.

Other oral reports list 20-30, 100 or 110 mg/kg without a clear salt basis. Equine 200 mg/kg has age-dependent maxima of 80 g adults, 60 g yearlings and 30 g foals. Poultry 100-500 mg/kg and citrate-specific bird regimens also have uncertain base equivalence; do not widen the explicit base range to include these amounts.