For food-producing animals, work through a veterinarian. In the U.S., extralabel drug use in food animals such as horses is permitted only under the direction of a licensed veterinarian, and meat/egg withdrawal periods must be observed per that veterinarian and the product's labeling. The information here is educational and is not directions for use. Note: Vetr WormGard is a piperazine product intended for dogs and cats, not for horses.
What piperazine treats in horses
In horses, piperazine treats the ascarid Parascaris equorum (a major parasite of foals and young horses), the pinworm Oxyuris equi, and, per some labels, small strongyles. It does not cover tapeworms or bots.
Piperazine dosage for horses
Label doses for horses cluster around ~110 mg/kg of piperazine base (roughly 88–200 mg/kg depending on the product), given via feed, water, or stomach tube. Use the calculator for a weight-based estimate and follow your product's directions.
Repeat the dose in about 4–6 weeks. Foals in particular benefit from repeat treatment as part of a season-long parasite program. Because ascarid resistance is a real concern, work with your vet on rotation and fecal egg-count monitoring.
How to give it
Piperazine can be top-dressed on feed, dissolved in water, or given by stomach tube (often by a vet). Dose to your horse's actual weight — use a weight tape or scale rather than guessing.
Safety notes for horses
Piperazine is well tolerated in horses. The main caution is in foals with heavy ascarid burdens: any effective dewormer can occasionally trigger an impaction colic from a large mass of worms, so heavily infected foals should be treated under veterinary guidance. Don't combine piperazine with pyrantel or levamisole.
See full safety, side-effect & overdose information →
Questions about piperazine for horses
Is piperazine good for deworming foals?
Yes — it's a traditional choice for Parascaris equorum in foals. But heavily infected foals should be treated with veterinary oversight because of the small risk of impaction colic from dying worms.
Does piperazine treat tapeworms or bots in horses?
No. It covers ascarids and pinworms (and some small strongyles per label), but not tapeworms or bots, which need other actives.
How do I know how much my horse weighs?
Use a weight tape or livestock scale for an accurate figure, then calculate the dose — estimating by eye often leads to underdosing.