Pergolide for horses is the cornerstone treatment for pituitary pars intermedia dysfunction (PPID), the hormonal disorder still widely known as equine Cushing's disease. If your horse or pony has recently been diagnosed, your vet has almost certainly prescribed pergolide — most often under the brand name Prascend. This guide explains what pergolide is, how it controls PPID, what to expect in the first few weeks, the side effects to watch for, and how the drug is monitored over the long term. It is written to help you feel confident managing a PPID horse, but it is general information only and never a substitute for your own vet's advice.
Table of Contents
What Is Pergolide?
Pergolide is a dopamine receptor agonist — a drug that mimics the action of dopamine, one of the brain's chemical messengers. It belongs to a group of medicines called ergoline-based dopamine agonists and works by binding to dopamine receptors and switching them on, much as the body's own dopamine would.
The drug was originally developed for people. Under the brand name Permax it was used to treat Parkinson's disease, a condition linked to falling dopamine levels in the brain. In 2007 pergolide was withdrawn from the human market in the United States after studies linked it to valvular heart disease, an effect traced to its activity at a serotonin receptor (5-HT2B) found in heart tissue. That withdrawal relates to long-term human use and does not reflect its safety record in horses, where it is given at far lower doses and has a very different risk profile. Today, pergolide's most important role by far is in veterinary medicine, as the treatment of choice for PPID in horses and ponies.
One practical point worth knowing: pergolide has a long duration of action, with an elimination half-life of around 27 hours. That is why a single daily dose is enough to keep working steadily around the clock.
PPID: The Condition Pergolide Treats
To understand why pergolide works, it helps to understand the condition it treats. Equine Cushing's disease — correctly called pituitary pars intermedia dysfunction (PPID) — is a progressive disorder of the pituitary gland. In a healthy horse, dopamine-producing nerve cells keep the pars intermedia region of the pituitary in check. In PPID, those nerve cells gradually degenerate, so the pars intermedia is no longer restrained and begins to overproduce hormones. The result is a cascade of hormonal imbalances that affect the whole body.
PPID is mainly a disease of older horses, with an average age at diagnosis of around 20 years, although it has been recorded in horses as young as seven. Native ponies and cob types — including breeds such as the Welsh Cob — appear to be affected more often, and any owner of an ageing pony should learn the signs. You can read more about age-related changes in our guide to horse life stages.
Common clinical signs of PPID include:
- Hirsutism — an abnormally long, thick, curly or slow-to-shed coat, the most recognisable sign of advanced PPID
- Excessive drinking and urination (polydipsia and polyuria)
- Abnormal fat deposits, particularly along the crest of the neck and above the eyes
- Lethargy, muscle loss and a pot-bellied appearance
- Recurrent infections and slow wound healing from a weakened immune response
- Laminitis, which is often the first and most serious sign to prompt investigation
Why Pergolide Works for PPID
Pergolide effectively replaces the dopamine signal that the failing nerve cells can no longer supply. By binding to dopamine receptors in the pars intermedia, it dampens the overproduction of hormones that drives PPID's clinical signs. It does not cure the disease — the underlying nerve degeneration continues — but it controls it, often very well, for the rest of the horse's life.
The evidence behind this is solid. Data from the Prascend Freedom of Information Summary showed that clinical signs began to improve within three months of starting treatment and continued improving through six months; three out of four treated horses were rated a treatment success; and delayed shedding improved in 89% of horses within six months. Independent work from the University of Minnesota reports an average treatment success rate of around 60 to 80%.
Prascend and Other Pergolide Brands
Prascend, made by Boehringer Ingelheim, was for many years the only licensed pergolide product for horses and remains the best known. It is a single-scored tablet, licensed specifically for the control of clinical signs of PPID.
In the UK, several licensed generic pergolide tablets are now also available, including Pergoquin and Dechra's Pergocoat. These contain the same active ingredient, pergolide mesylate, and are prescribed and dosed in the same way. Because they compete with Prascend, generics can sometimes reduce the ongoing cost of treatment — ask your vet or veterinary pharmacy what they stock.
You may also come across compounded pergolide, prepared by a pharmacy as a paste or liquid rather than a licensed tablet. These can be useful for fussy horses or awkward doses, but unlicensed compounded formulations may be less stable, so they should only ever be used on your vet's recommendation.
How Pergolide Is Given to Horses
Pergolide is given by mouth, once a day, usually mixed into a small feed or hidden in a treat such as a piece of apple. Prascend tablets are single-scored so they can be split cleanly when the dose needs adjusting.
The licensed starting dose is 2 micrograms per kilogram of bodyweight once daily — roughly 1 mg a day for an average 500 kg horse — and the dose can be titrated upward, to a maximum of around 4 micrograms per kilogram, if the response is not sufficient. In practice many vets prefer to start low and go slow, beginning below the standard dose and increasing gradually while watching the horse's response and its blood results. The aim is always to find the lowest dose that controls the signs. These are general figures only: the exact starting dose, any increases, and the final maintenance dose must be set by your prescribing vet for your individual horse, based on its weight, clinical signs and hormone testing.
Missed Doses
If you forget a dose, give it as soon as you remember. If it is nearly time for the next dose, simply skip the missed one and carry on as normal the following day — do not double up to make up for it. Because pergolide has a long half-life, one occasional missed dose is unlikely to cause a problem, but consistent daily dosing gives the best long-term control. If several doses are missed, your horse may effectively be starting again, and it is worth speaking to your vet.
Storage
Store pergolide tablets at or below 25°C, in their original packaging and out of direct light. Keep them well out of reach of dogs, cats and children: cases have been reported of dogs eating tablets dropped during dosing or left in horse feed.
The Pergolide Veil: What to Expect When Starting
Many owners are caught off guard when, a few days after starting treatment, their horse goes off its food and seems dull or withdrawn. This transient reaction is so common that it has earned a nickname among owners and vets: the "pergolide veil". It typically shows up in the first week or two as reduced appetite, mild lethargy and a slightly flat mood, and it usually passes on its own as the horse adjusts to the medication.
You can make the transition easier by:
- Starting at a low dose and building up gradually, as directed by your vet
- Splitting the introduction of the dose over a couple of weeks if your vet advises it
- Tempting the appetite with palatable, low-sugar feeds and keeping mealtimes calm
- Giving the tablet with food rather than on an empty stomach
Contact your vet if the loss of appetite is severe, if your horse stops eating altogether, or if the dullness does not lift after a couple of weeks. A brief dose reduction, followed by a slower re-introduction, usually resolves it without abandoning treatment.
Pergolide Side Effects in Horses
Pergolide is generally well tolerated, and most side effects are mild, dose-related and temporary. By far the most common is the reduced appetite of the pergolide veil described above. Others include mild weight loss, lethargy, diarrhoea or loose droppings, and occasional behavioural changes such as anxiety. The table below summarises what to watch for and how each is usually managed.
| Side effect | How common | Typical management |
|---|---|---|
| Reduced appetite ("pergolide veil") | Common, first 1–2 weeks | Start low, tempt with palatable feed; short dose reduction if severe |
| Mild lethargy or dullness | Common early on | Usually self-limiting as the horse adjusts |
| Weight loss | Occasional | Review diet and dose with your vet; monitor body condition |
| Loose droppings or mild colic signs | Uncommon | Report to your vet; dose may be adjusted |
| Behavioural change (anxiety, quietness) | Uncommon | Usually resolves; discuss with your vet if persistent |
Because appetite and weight are both signs to watch, it is worth getting comfortable with body condition scoring so you can track subtle changes over time. Pergolide should not be used in horses with a known hypersensitivity to pergolide mesylate or other ergot derivatives, and it has not been fully evaluated in pregnant or lactating mares — your vet will weigh the risks in those cases.
Monitoring a Horse on Pergolide
PPID is managed by response, and that means regular monitoring. The main laboratory tool is a blood test measuring the hormone ACTH (adrenocorticotropic hormone), which is elevated in PPID. Your vet uses it both to confirm the diagnosis and to judge whether the current pergolide dose is doing its job. In early or borderline cases, a TRH stimulation test may be used because it is more sensitive than a single resting ACTH measurement.
Two points make monitoring more nuanced than a simple pass or fail. First, ACTH results are interpreted against seasonally adjusted reference ranges, because ACTH naturally rises in late summer and autumn in all horses. Second, that same autumn rise means many PPID horses need a temporary dose increase between roughly August and October, then a return to their usual dose afterwards. Alongside the blood work, your own observations matter enormously: coat quality, energy, drinking, weight and — above all — any hint of laminitis.
As a rough guide, ACTH is often re-checked a few weeks to a couple of months after starting or changing the dose, and then at least once a year, ideally timed consistently. Your vet will set the exact schedule for your horse. Because PPID so often travels alongside insulin problems, many horses are also screened for equine metabolic syndrome and insulin dysregulation, which sharply raise the risk of laminitis.
Medication is only part of the picture. Good management — a low-sugar, low-starch diet, careful grazing control, sensible exercise and prompt attention to hoof health — works hand in hand with pergolide. Our guides to managing a laminitic horse and practical hay alternatives are useful companions for owners of PPID horses.
Handling and Safety
Pergolide is safe to handle sensibly, but a few precautions matter. Do not crush the tablets: crushing creates dust that can be inhaled, and pergolide — like other ergot derivatives — can cause nausea, dizziness, lethargy and low blood pressure in people who are accidentally exposed. Wash your hands after dosing.
Pregnant or breastfeeding women should wear gloves when handling the tablets and avoid handling broken or crushed ones. As noted above, keep the medication well away from dogs and other pets, which are far more sensitive to it than horses. If anyone accidentally swallows a tablet, contact a doctor.
Cost and Availability
Pergolide is a prescription-only medicine, so you will need a diagnosis and a prescription from your vet before you can buy it. Once you have a prescription, tablets can be bought from your vet directly or from a licensed online veterinary pharmacy, which is often cheaper. Cost depends on your horse's dose and bodyweight, since a larger horse on a higher dose uses more tablets, and it has fallen for many owners since licensed generics such as Pergoquin and Pergocoat joined Prascend on the market. Treatment is lifelong, so it is worth budgeting for it as an ongoing cost and factoring in the periodic blood tests as well. Buying in larger quantities on a repeat prescription can help keep the price per tablet down.
Living with PPID Long Term
A PPID diagnosis is not the ending it once was. With daily pergolide and good management, most horses regain their energy, shed their coats more normally, and go on to enjoy years of comfortable, active life. The disease is progressive, so the dose may need to creep up over time and monitoring never fully stops, but the great majority of horses respond well, especially when treatment starts early.
The most important thing you can do is stay consistent: give the tablet every day, keep to your monitoring schedule, control your horse's diet and weight, and act quickly at the first sign of laminitis. If your horse is one of the minority that responds poorly to pergolide even at higher doses, your vet may discuss adding or switching to another dopamine agonist such as cabergoline. For the vast majority, though, pergolide alone does the job — quietly, once a day, for the rest of a happy retirement.
Frequently Asked Questions
How long does pergolide take to work in horses?
Some owners notice improvements in energy and drinking within a few weeks, but the more visible signs take longer. Clinical studies show improvement building over the first three months and continuing to six months, with coat quality among the last things to change — often only after the next shedding season. Pergolide is a long game, not a quick fix.
What are the most common side effects of pergolide?
Reduced appetite in the first week or two — the "pergolide veil" — is by far the most common. Mild lethargy, slight weight loss and, less often, loose droppings or quieter behaviour can also occur. Most side effects are mild and settle as the horse adjusts or after a small dose adjustment by your vet.
Can you stop pergolide once your horse improves?
No. Pergolide controls PPID but does not cure it, so stopping treatment allows the clinical signs to return. Horses that respond well stay on pergolide for life. Never stop or change the dose without speaking to your vet.
What is the difference between pergolide and Prascend?
They are the same medicine. Pergolide is the active ingredient (pergolide mesylate); Prascend is Boehringer Ingelheim's brand name for it. Licensed generics such as Pergoquin and Pergocoat contain the identical active ingredient and are used in exactly the same way.
Why does my horse need more pergolide in autumn?
Every horse experiences a natural seasonal rise in the hormone ACTH in late summer and autumn, and in PPID horses this rise is exaggerated. Many need a temporary dose increase between roughly August and October to stay well controlled, returning to their usual dose afterwards. Your vet will guide any seasonal adjustment based on your horse's blood results.
This article is for general information and does not replace veterinary advice. Pergolide is a prescription-only medicine: always follow the guidance of the vet who has examined your horse. If you think your horse may have PPID, or you have concerns about a horse already on treatment, speak to your vet.
