Piperazine: veterinary dose and monograph

At a glance

Drug class

Antiparasitic

Also known as

Piperazine citrate, Pinworm syrup, Wormaway

Species with doses

Dogs, Cats, Horses, Pigs, Poultry, Rabbits and Reptiles

General dose range

45–65 mg/kg PO single dose (repeat in 2–3 weeks) — check the species tables for the indication

Routes

PO

Last reviewed

1 October 2026

Indications

• Ascarid (large roundworm) infections in dogs, cats, foals, pigs and poultry
• Routine roundworm deworming where only ascarids are targeted
• Deworming of young or debilitated animals needing a very-low-toxicity option

Piperazine dose by species

Doses are per administration unless stated. mg/kg doses scale with body weight; per-animal, per-quarter and infusion-rate doses are shown as the reference writes them.

Dogs

• Ascarids (roundworms): Papich 5e: 44–66 mg/kg PO once. Plumb’s p.982: 45–65 mg/kg of base PO (pups under 2.5 kg max 150 mg) (Cornelius & Roberson); other sources 100–110 mg/kg. Salts contain different amounts of base — check the product. Repeat in 2–3 weeks (larvae in tissues are unaffected).

Cats

• Ascarids: Papich 5e: 44–66 mg/kg PO once. Plumb’s p.982: 45–65 mg of base/kg (maximum 150 mg in kittens); 100–110 mg/kg in other sources. Repeat in 2–3 weeks.

Horses

• Parascaris equorum (foals): Papich 5e: horses and pigs 110 mg/kg PO (or 30 mL of 17% solution per 45 kg). Plumb’s p.982 (Roberson 1988): 110 mg/kg (base) PO, repeat in 3–4 weeks; 10-weekly retreatment for P. equorum in young horses. Heavy burdens risk impaction when killed en masse.

Pigs

• Ascaris suum: Papich 5e: horses and pigs 110 mg/kg PO in the drinking water as the sole water source. Plumb’s (swine): 110 mg/kg as base — citrate usually in feed as a one-day treatment, hexahydrate in water; the dose must be consumed within 8–12 h (withhold feed or water overnight); retreat in 2 months. Plumb’s notes swine withdrawal times are not determined — follow the product label.

Poultry

• Ascaridia galli: Plumb’s p.982 (Roberson 1988): 32 mg/kg as base (~0.3 g per adult bird) in each of 2 successive feedings or for 2 days in drinking water; poultry 100–500 mg/kg once, repeat in 10–14 days (Clubb 1986). Not effective in psittacines. Follow the product-label withdrawal.

Rabbits

• Pinworms (Passalurus): Plumb’s p.982 (Ivey & Morrisey 2000): piperazine citrate 100 mg/kg PO q24h for 2 days (adipate 200–500 mg/kg in adults); or 3 g/L in drinking water for 2 weeks (Burke). Wash the perianal area.

Reptiles

• Nematodes: Plumb’s p.982 (de la Navarre 2008): 40–60 mg/kg PO, repeat in 2 weeks, faecal check 14 days later.

Contraindications

Severe hepatic or renal impairment (reduced clearance — neurotoxicity risk). Gastrointestinal obstruction or impaired motility (relies on normal peristalsis to expel paralysed worms; heavy ascarid burdens can cause obstruction as worms detach). Chronic use. Known hypersensitivity.

Species-specific warnings

Horses: Heavy Parascaris burdens in foals can impact/obstruct the small intestine when worms are killed — consider a less abrupt approach in known heavy infections.

Adverse effects

• Generally minimal — occasional vomiting/diarrhoea
• Neurotoxicity (ataxia, tremor) at overdose or with impaired clearance
• Possible obstruction with very heavy ascarid burdens (worm bolus)

Drug interactions

• Pyrantel/morantel/levamisole (spastic-paralysis agents): pharmacologically antagonistic (flaccid vs spastic paralysis) — do not combine
• Chlorpromazine/phenothiazines: increased risk of neurotoxicity/seizures (reported)
• Purgatives: historically combined to aid expulsion (rarely needed)

Pregnancy and lactation

Considered safe in pregnancy at label doses (very low toxicity).

Monitoring

• Faecal egg count (ascarids) and repeat dosing at 2–3 weeks
• For heavy burdens (foals), watch for colic/impaction after treatment
• Neurologic signs if hepatic/renal impairment

Toxicity and overdose

Extremely wide safety margin; overdose can cause reversible neurotoxicity (ataxia, muscle tremor, head pressing) especially with hepatic/renal impairment. Massive ascarid kill can rarely cause GI obstruction.

Management: Supportive — neurologic signs are usually reversible with discontinuation and time; fluids and nursing care. No specific antidote. Manage any obstruction surgically/medically as needed.

Clinical pearls

• Cheap, OTC and extremely safe — but it ONLY kills ascarids; it misses hookworms, whipworms and tapeworms
• Works by flaccid paralysis (GABA agonist) — never combine with pyrantel/levamisole (spastic paralysis): they cancel out
• In heavily parasitised foals, mass worm death can cause impaction — deworm thoughtfully
• Largely superseded by broad-spectrum dewormers, but handy for a quick, safe ascarid clean-out in young animals

Mechanism of action

Acts as a GABA-receptor agonist at the nematode neuromuscular junction, hyperpolarising muscle and causing flaccid paralysis of the worm. The paralysed (but living) ascarids lose their grip on the gut wall and are expelled by normal intestinal peristalsis — which is why adequate gut motility is needed and why a massive worm load can occasionally cause obstruction.

Formulations and products

• Oral syrup/solution (various strengths)
• Oral powder (water/feed)
• Tablet
• Piperazine syrup/powder (vet) (Various (India)) — Piperazine citrate/adipate, Syrup / powder / tablet
• Piperazine citrate (pinworm/roundworm syrup) — Syrup, Oral syrup (human-label)

Storage

Syrup/powder/tablets: 15–30 °C, protect from light; keep tightly closed.

Before you use this dose

Reference doses for veterinary professionals. Confirm the dose against the product label, the patient’s condition, current guidance and local regulations before use; the attending veterinarian remains responsible for every clinical decision.

Other antiparasitics

• Nitroxynil
• Oxfendazole
• Oxibendazole
• Permethrin
• Ponazuril
• Praziquantel
• Pyrantel pamoate
• Pyrimethamine

Frequently asked questions