Prascend for Horses: Cushing's (PPID) Dosing, Side Effects and the 'Pergolide Veil'

Prascend and PPID by the Numbers

Sources: McGowan et al. 2013 · Ireland & McGowan 2018 · Prascend FDA label (DailyMed) · Kirkwood et al. 2022 · Schott et al. 2025

Free download · from a Colorado hemp farm

Free: The Horse Owner’s Guide to CBD & Hemp

40 pages. The Tarleton State horse studies, competition rules, and serving size by weight.

Instant download, plus 25% off your first bottle.

Get the free horse guide →

Written by Marc Brannigan and Natalie Mondine, co-founders of HempMy Pet.

What PPID (Equine Cushing's) Actually Is

A brain problem that shows up as a coat problem.

Pituitary pars intermedia dysfunction, or PPID, is an age-related degenerative disease of the nerve cells that control one part of the pituitary gland. In a healthy horse, dopamine-releasing neurons in the hypothalamus act like a brake on the middle lobe of the pituitary, the pars intermedia. Dopamine binds to D2 receptors there and holds down production of a family of hormones made from a parent molecule called POMC: ACTH, alpha-MSH, beta-endorphin and others (Kirkwood, Hughes & Stewart, Veterinary Sciences 2022).

As those dopamine neurons degenerate with age, the brake fails. The pars intermedia enlarges, sometimes into a benign tumour (an adenoma), and pumps out too much of those hormones. The long coat, muscle loss, sweating and infections all follow from that excess. "Cushing's" is the older name, borrowed from a human disease that works differently; vets now prefer PPID because the problem starts in the pars intermedia, not the adrenal glands.

The Kirkwood review calls PPID the most common endocrine disease of geriatric horses, affecting 20 to 25% of horses over 15. The most robust single prevalence figure comes from an Australian study that visited owners and tested every horse aged 15 or older: 21.2% had PPID, even though owners rarely listed it as a known problem (McGowan, Pinchbeck & McGowan, Equine Veterinary Journal 2013). Across all ages the estimate is 2.9%, and in a systematic review only increasing age was confirmed as a risk factor; breed and sex findings were inconsistent (Ireland & McGowan, Veterinary Journal 2018). The review notes that PPID is rare under 10, and that the youngest reported cases were 7 years old. If you have a horse in its late teens or twenties, our guide to how long horses live puts that age in context.

The Signs of PPID

Delayed shedding first, then everything else.

In the McGowan study, owner-reported hirsutism (a long coat or delayed shedding) was the one clinical sign that stayed significant after accounting for age, with 7.8 times the odds of PPID. Routine bloodwork, by contrast, showed nothing useful. The authors' advice was simple: aged horses with these signs, especially a coat that will not shed, should be tested. Here is the full list from the literature, with what each looks like in the barn.

Frequencies from Kirkwood et al. 2022, which pools the studies behind each figure, and Ireland & McGowan 2018.

The review stresses that mildly affected horses may show only subtle signs, such as delayed shedding, which are easy to put down to age. That matters, because the same review says recognising early signs and starting treatment improves quality of life. A 2026 study of 213 horses in two university primary-care practices found that a younger age at diagnosis was linked to both hormone normalisation and survival (Stapley et al., Journal of Veterinary Internal Medicine 2026). The most common reason those horses were first tested was a long coat or delayed shedding (40.5%), followed by suspected insulin dysregulation (26.8%) and non-laminitic lameness such as hoof abscesses (19.0%).

How Vets Test for PPID, and Why the Season Matters

One blood test, read against the calendar.

1. Clinical picture. In an older horse with an obvious long coat, the review says a diagnosis can be made on signs alone, and testing is recommended mainly when treatment is affordable, when early or severe disease is suspected, or to track response to treatment. Testing horses with no signs at all is not currently recommended.
2. Basal (resting) ACTH. The standard first test. A single blood sample in an EDTA tube, kept chilled at about 4 °C and analysed as soon as possible, ideally within 24 hours. It can be taken at any time of day, and paired samples add nothing over a single one.
3. Seasonal cut-offs. ACTH rises in late summer and autumn in every horse, and rises much more in horses with PPID. That is why labs use different cut-off values by month. In the review's data, basal ACTH was still accurate in early autumn and was most accurate in mid-to-late autumn (October and November in the Northern Hemisphere), when the gap between normal and PPID horses is widest.
4. TRH stimulation test. For early or mild cases, or when the basal result falls in the equivocal zone, ACTH is measured before and 10 or 30 minutes after an IV dose of TRH (1 mg for horses, 0.5 mg for ponies). The review describes it as more accurate than basal ACTH. TRH is available as a compounded product in the US.
5. Insulin testing. Not a PPID test, but the review recommends checking insulin in horses with regional fat or a history of laminitis, because it changes how they are fed and managed. More on this below.

One honest note on accuracy. The review cites a median sensitivity for basal ACTH of 75.5% and specificity of 95.2% in one analysis, and 66% and 87% in another. In plain English: a high result is usually right, but a normal result in a mildly affected horse can miss the disease. The review says basal ACTH is less accurate for detecting PPID unless signs are severe, and is not recommended for screening or for early disease. If your horse looks like a PPID horse and the basal result is borderline, ask about retesting or a TRH stimulation test rather than ruling it out.

How Prascend Works

It replaces the missing dopamine signal.

Pergolide is a synthetic ergot-derived drug that stimulates dopamine receptors, the same receptors the failing neurons used to stimulate. According to the label, it has been shown to lower plasma ACTH, MSH and other POMC peptides in horses with PPID. The Kirkwood review calls pergolide the treatment of choice and the only drug registered for PPID, and notes that it acts on the pars intermedia within hours of an oral dose.

What it does not do matters as much. The review says pergolide does not reverse the underlying pituitary pathology, and in one small study pituitary size measured on CT increased even while clinical signs improved. Treatment is therefore for life. Stop the tablets and the brake comes off again.

Does Prascend Work?

Yes for most horses, measured over months rather than weeks.

The FDA approval rests on an open-label, historical-control field study of 122 horses, 113 of them included in the effectiveness analysis. Every horse had a long coat and an abnormal endocrine test at entry. All started at 2 mcg/kg once daily; horses whose endocrine test at day 90 was still abnormal went up to 4 mcg/kg. 47 of 113 (41.6%) needed that increase. At day 180, 86 horses (76.1%) were counted as treatment successes on endocrine testing and clinical scores.

Percent of horses improved relative to baseline scores, Table 4 of the Prascend FDA label. Open-label, no placebo group.

Read that table carefully. The coat responds best, and it takes time: one horse in three looked better at three months, nine in ten by six months. Muscle and fat respond in fewer than half. The review adds a caveat on muscle: the 46% figure came from a subjective score with no control group, and a separate study found pergolide did not change markers of muscle breakdown.

The longest follow-up is a 2025 study that kept 30 equids from the original field trial on Prascend for up to 14.5 years (Schott et al., Journal of Veterinary Internal Medicine 2025). After 5.5 years, owners of the 13 surviving equids reported sustained clinical improvement, and endocrine tests had normalised in 75% of them. After 9.5 years, only two of six survivors still had normal tests. The finding owners will care about most: many horses stayed well on their starting dose for years, rather than needing steady increases. Seven of the 13 on the lower dose did go up to 4 mcg/kg, between 1.7 and 4.7 years in.

Prascend Dosage for Horses

Your vet sets the dose. These are the label limits.

The label starting dose is 2 mcg/kg by mouth once daily. That is the same as 0.002 mg/kg, the figure most guides quote, and works out to 1 mg for a 500 kg (1,100 lb) horse. The dose may be adjusted to effect, not to exceed 4 mcg/kg daily, and the label says to titrate to the lowest effective dose. Tablets are 1 mg, light red and half-scored, so doses are rounded to the nearest half tablet.

Table 1 of the Prascend FDA label. Prescription only.

Adjusting the dose. The label bases adjustments on improvement in clinical signs and on follow-up endocrine tests such as resting ACTH. The review recommends rechecking ACTH and signs about one month after starting, then titrating in steps of 0.001 mg/kg (1 mcg/kg) with monthly reassessment, and notes that because pergolide acts quickly, an earlier check can make sense. Both doses in the review and on the label are once a day.

How to give it. Tablets are usually given in a treat or a handful of feed; in the label's safety study, doses were dissolved in about 10 mL of sugar water. The label is specific about human safety: do not crush the tablets, and take care when splitting them, because people have reported eye irritation, an irritating smell and headache. Pregnant or nursing women should wear gloves, and anyone who has reacted to ergot drugs should not handle them. Keep the box locked away from dogs: the label warns that dogs have eaten tablets dropped in feed and had adverse reactions.

Drug interactions on the label. Dopamine antagonists such as phenothiazine tranquilisers (acepromazine is one), domperidone and metoclopramide ordinarily should not be given with Prascend, because they can reduce its effect. Prascend is about 90% bound to plasma proteins, so the label advises caution with other drugs that affect protein binding. Make sure every vet who treats your horse knows it is on pergolide.

The "Pergolide Veil": Appetite Loss on Prascend

Common, usually temporary, and manageable with your vet.

"Pergolide veil" is barn slang, not a medical term. Owners use it for the dull, off-feed, slightly flat horse some of them see in the first weeks on pergolide. The label's word is inappetence, and it gives the clearest numbers anywhere: 40 of 122 horses (32.8%) had decreased appetite at one or more meals, compared with 1.6% of owners reporting appetite problems before treatment. Most cases were transient and occurred during the first month, but some horses had sporadic episodes throughout the six months. Lethargy was reported in 9.8% of horses on treatment and in none at baseline, which fits the "veil" description. The 14-year follow-up found the same pattern: decreased appetite was reported in 33% of equids.

The label also shows how rarely it forced a change. Only two horses needed a temporary dose reduction for inappetence during the first month, and both were back on their original dose within 30 days. One owner in the long-term study stretched the dosing interval to every 48 hours a few times when appetite dropped, a decision to make with your vet rather than on your own.

What the label tells vets to do. If signs of dose intolerance develop, decrease the dose by half for 3 to 5 days, then titrate back up in 2 mcg/kg increments every 2 weeks until the desired effect is reached. The review describes the same approach: reduce the dose, then increase it gradually over weeks. If your horse goes off feed on Prascend, call your vet before stopping or changing the tablet.

Other Side Effects and What to Watch

Table 2 and text of the Prascend FDA label. No placebo group, so not every reaction was caused by the drug.

Context matters for that table. These were old horses with an active disease, followed for six months with no untreated comparison group, so some lameness, colic and deaths reflect age and PPID rather than pergolide. Eight horses died or were euthanised during the study, from worsening pre-existing conditions or colic. Post-approval reports, which the label says cannot establish cause or frequency, add anorexia, weight loss, hair loss, sweating, muscle stiffness, ataxia, seizures, tremors, aggression, hyperactivity, "stud-like" or spooky behaviour, anaemia, elevated liver enzymes and low platelets, some at starting doses and some after a dose increase.

The safety study in healthy horses at up to twice the maximum dose found lower heart rates, slightly higher temperatures and mild drops in red cell counts that generally returned to pre-treatment levels after the first 30 to 60 days. The label also warns that the effects on breeding, pregnant or nursing mares have not been evaluated, and that pergolide suppresses prolactin, which may interfere with milk production. Do not use it in horses intended for human consumption.

Prascend, Insulin and Laminitis

The complication that decides most outcomes.

Laminitis is the PPID complication owners fear most, and for good reason: it was the cause of euthanasia for five of the 29 equids that died or were put down in the 14-year Prascend study. But the evidence points at insulin, not ACTH, as the driver. When pathologists examined the hooves of 16 PPID horses after death, every horse with PPID and laminitis had high fasting insulin (median 74.1 µIU/mL), while PPID horses without laminitis had insulin below the upper reference limit, and their hoof lamellae looked normal next to age-matched controls. The authors concluded that it may be only the high insulin that is linked to the lamellar damage (Karikoski et al., Equine Veterinary Journal 2015).

That overlap is common. The Kirkwood review reports that of 325 horses with PPID, 32% had high non-fasting insulin, and 66% of those had laminitis. Whether pergolide helps the insulin side is less clear. The review states that pergolide has no effect on insulin concentration. A 2025 randomised crossover study added nuance: in eight matched pairs of horses and ponies given pergolide at 2 mcg/kg for four weeks, insulin sensitivity did not change in any group, but the insulin spike after a standard meal was lower in horses with both PPID and insulin dysregulation, and unchanged in horses with insulin dysregulation alone (Galinelli et al., Equine Veterinary Journal 2025).

The practical message is the one the review gives: ACTH does not predict laminitis risk, so ask your vet to test insulin as well, and if your PPID horse is insulin dysregulated or has had laminitis, avoid feeds high in sugar and starch. Do not starve a thin PPID horse to get there; the review warns that these horses often lose weight and muscle, and that diets should be built around insulin status and body condition. Our sibling guide to laminitis in horses covers the hoof side in depth.

Compounded Pergolide vs Prascend

Same drug, very different shelf life.

Compounded pergolide is still prescribed. In the 2026 primary-care study, 95.7% of horses with recorded treatment at diagnosis were on the labelled product and 4.3% on a compounded form, while 11.3% used a compounded form at some point.

The stability evidence is the reason vets prefer the tablet. A 2009 stability study compounded pergolide into an aqueous liquid at 1 mg/mL and measured it over 35 days. Samples stored at room temperature in the light had excessively degraded by day 14; at body temperature by day 21; and at room temperature in the dark by day 35. The authors recommended that compounded aqueous pergolide be kept in a dark container, refrigerated, used within 30 days, and thrown away if it changes colour (Davis et al., JAVMA 2009). The Kirkwood review echoes that the tablet form should be recommended where possible.

What Prascend Costs, Honestly

We are not going to quote a price, because pharmacy, vet-clinic and online prices change and vary widely. What we can give you are the cost drivers. A typical 1,000 lb horse on the starting dose takes one tablet a day, 365 tablets a year, and Prascend comes in boxes of 60 or 160 tablets. Horses that need 4 mcg/kg take twice that. Add the follow-up ACTH tests, insulin tests and the usual extra hoof, dental and parasite care a PPID horse needs.

Money affects outcomes, and the research says so plainly. In the 213-horse primary-care study, the owner's county household income was independently linked to both clinical improvement and survival, alongside a healthy body condition score and frequent monitoring. In the 14-year study, 87% of owners said they would treat another PPID horse for life, but cost would be a factor: only 17% were willing to pay $1,500 or more a year. If cost is a worry, tell your vet early. Spacing tests sensibly and keeping the horse at a healthy weight are both low-cost ways to stack the odds.

Managing a PPID Horse Beyond the Tablet

Pergolide controls the hormones. Management protects the horse.

• Feed to insulin status and body condition. Low sugar and starch for insulin-dysregulated or laminitic horses; extra calories for thin ones. In the primary-care study, a body condition score of 4 to 6 out of 9 at diagnosis carried 15 times the odds of clinical improvement.
• Clip and provide shade and water. The review recommends body clipping, shade and fresh water for horses that struggle to regulate temperature because of their coat or sweating.
• Dental checks. Older PPID horses often have dental disease. Horses that cannot manage long hay can be fed chopped fibre or beet pulp to keep intake up.
• Parasite control by fecal egg count. PPID horses are more prone to infections and heavier worm burdens, so the review advises regular fecal egg counts.
• Hoof care. Regular farriery, and corrective work for any laminitic changes.
• Monitoring. Retest ACTH as your vet advises. Shorter gaps between tests were linked to hormone normalisation in the primary-care study.

When to Call the Vet

• Same day: any sign of laminitis (shifting weight, reluctance to walk, a strong digital pulse, a hot foot), colic, a horse that has stopped eating entirely, neurological signs such as stumbling or tremors, or a seizure.
• Within days: appetite loss that lasts beyond a few meals, new aggression or agitation after a dose change, diarrhea, steady weight loss, or a recurrent abscess or infection.
• At the next visit: a coat that still is not shedding after a season on pergolide, ongoing muscle loss, or questions about dose, cost or compounded versions.
• Before adding anything: any new supplement, including hemp or CBD, and any sedative, because some tranquilisers can reduce Prascend's effect.

What to Do If You Suspect Cushing's in Your Horse

1. Write down and photograph what you see. Shedding dates, coat length, topline, hoof rings, water intake. Photos taken a year apart are often the clearest evidence.
2. Book a vet visit and ask for a resting ACTH test. Ask how your lab adjusts for season, especially in late summer and autumn.
3. Ask about insulin testing at the same time. It tells you how to feed the horse and how worried to be about laminitis.
4. If the result is borderline, ask about retesting or a TRH stimulation test rather than ruling PPID out.
5. Start Prascend at the dose your vet prescribes, give it at the same time daily, and handle the tablets with care.
6. Watch appetite closely for the first month. Call your vet rather than stopping the drug if the horse goes off feed.
7. Recheck ACTH and signs after about a month, then on the schedule your vet sets. Judge the coat at the next shedding season.
8. Build the management routine. Diet, clipping, teeth, worming by egg count and regular hoof care.

Where Hemp Fits — and Where It Doesn't

We sell hemp oil for horses, so here is the honest version.

Hemp has no role in treating PPID. No study has tested CBD or hemp in horses with PPID. Nothing in hemp replaces the dopamine signal that pergolide provides, and nothing on the market has been shown to lower ACTH, restore shedding or protect the hooves of a PPID horse. If a brand suggests otherwise, it is ahead of the evidence. Pergolide is the treatment. Full stop.

There is also a specific caution for these horses. In a 2026 randomised study of 13 Connemara ponies, seven of them with equine metabolic syndrome, ponies given CBD at 2 mg/kg twice daily for 21 days had a significant rise in their insulin response to an oral sugar test (mean change +10.74 µIU/mL, p = 0.046), while the control group on flaxseed oil did not. CBD did not change weight, body condition, neck crest, glucose or triglycerides, and was otherwise well tolerated. The authors called the clinical relevance unclear but said it may raise concerns about CBD in horses prone to metabolic syndrome (Wermer et al., Frontiers in Veterinary Science 2026). That dose is several times the 0.3 to 0.6 mg/kg range in the Tarleton studies of our own formula, but it is exactly the kind of horse many PPID horses are. We wrote the study up in full: CBD, metabolism and insulin in ponies.

Here is what the equine research does show. In a randomised study of mature horses with mild joint osteoarthritis, horses given CBD oil alongside phenylbutazone had a median Horse Chronic Pain Scale score of 3, against 7 in horses given phenylbutazone alone (Interlandi et al., Frontiers in Veterinary Science 2024). Joints, not PPID, and a small trial. Our own equine formula was studied at Tarleton State University: a single serving lowered stall behaviours such as pawing compared with a control oil (P = 0.03), and a dose study found no adverse effects at 0.3 or 0.6 mg/kg (Turner et al., Journal of Animal Science 2021). Daily dosing over five days showed no behaviour difference, and the transport arm found no significant change in cortisol.

So the honest role for hemp in a PPID horse is small and conditional: if your vet has tested insulin and is comfortable with it, a hemp oil can be one part of an old horse's routine to support comfort, normal movement and a calm, settled state, alongside pergolide and good management, never instead of them. Our guide to CBD for senior horses covers that wider picture.

Before you start:

• Get insulin tested and tell your vet. Because of the Connemara pony finding, be especially careful with insulin-dysregulated or laminitis-prone horses. In another equine study, liver enzymes rose in 8 of 12 horses on CBD and returned to normal within 10 days of stopping (Yocom et al. 2022). Post-approval reports for Prascend also list elevated liver enzymes, so your vet may want bloodwork.
• Competition horses: cannabinoids are prohibited under FEI, USEF and HISA rules, and there is no published withdrawal time. Use hemp for pleasure, rehab, retired and rescue horses only. More in our horse safety guide.
• Dose by weight, low end first. One pump of our 5,000 mg oil is about 20 mg. The Tarleton studies used 0.3 to 0.6 mg/kg. Full chart in our horse dosing guide.
• Never change the pergolide. Never start, stop or change your horse's prescription without your veterinarian.

Ranges follow the 0.3–0.6 mg/kg range used in the Tarleton studies of our formula. A bottle holds about 250 pumps. Start at the low end, and with your vet's agreement for any PPID or insulin-dysregulated horse.

Questions to Ask Your Vet

• Which month's cut-off is my horse's ACTH result being read against, and is it in the equivocal zone?
• Should we test insulin too, and how should I feed based on the result?
• What dose are we starting at, and when do we recheck ACTH?
• What should I do if my horse goes off feed in the first weeks?
• Is Prascend or a compounded form better for my horse, and how should I store it?
• Are any of my horse's other drugs or sedatives a problem with pergolide?
• Is a supplement such as hemp oil reasonable for this horse, given its insulin status?

Frequently Asked Questions

Shop the Equine Formula → All Hemp for Horses

The Short Version

PPID is common in older horses, about one in five over 15, and the first sign is usually a coat that will not shed. A resting ACTH test read against seasonal cut-offs, plus a TRH test when the result is borderline, confirms it. Prascend at 2 mcg/kg once a day, up to 4 mcg/kg, controls the signs in most horses, though it takes months and never cures the disease. Expect possible appetite loss in the first month and work through it with your vet. Test insulin too, because insulin, not ACTH, is what drives laminitis. Hemp does not treat PPID, and given the insulin finding in ponies, it should only be added with your vet's agreement.

Laminitis in Horses · CBD for Senior Horses · How Long Do Horses Live? · CBD & Insulin in Ponies · Magnesium for Horses · Bute for Horses · Is CBD Safe for Horses?

These statements have not been evaluated by the Food and Drug Administration. These products are not intended to diagnose, treat, cure, or prevent any disease. This article is general information, not veterinary advice. Prascend is a prescription drug; never start, stop or change your horse's prescription without your veterinarian. Consult your veterinarian before using any supplement, especially if your horse has PPID, insulin dysregulation or a history of laminitis, or is pregnant, nursing, competing, or taking medication.