Pergolide is a dopamine agonist that is helpful in controlling the symptoms associated with equine pituitary pars intermedia dysfunction (PPID, equine Cushing’s disease).¹ The most common endocrine disorders encountered by equine practitioners and owners are pituitary pars intermedia dysfunction (PPID or Cushing’s Syndrome) and equine metabolic syndrome (EMS).

The acronym PPID is more widely used for this disease, as it provides a more accurate name. Another acronym, pars intermedia pituitary adenoma (PIPA), is also occasionally used. Cushing’s disease in people and other mammals differs in some important aspects; the affected portion of the pituitary gland is different, thus the use of the human medical term “Cushing’s” can be misleading.² Pituitary pars intermedia dysfunction and equine metabolic syndrome are often encountered in aging horses and may present with several recognizable signs, including laminitis.³

In the normal equine pituitary gland, specific cells called melanotropes receive neural input from the hypothalamus, causing neurons to release dopamine. The dopamine then inhibits the intermediate lobe of the pituitary gland from producing several different hormones. In the diseased pituitary gland, the hypothalamic neurons degenerate, resulting in dramatically lower dopamine levels.²

Common signs of PPID in horses include:

• Failure to fully shed
• Long, curly coat (often along the jaw line with feathering near the fetlocks)
• Chronic infections
• Repeated occurrences of laminitis with hoof abscesses
• Excess sweating
• Polyuria/polydipsia (PU/PD)
• Lethargy
• Loss of muscle mass (in untreated horses)
• Pot-bellied appearance
• Infertility, or lack of estrus cycles
• Abnormal development of mammary glands

Equine Metabolic Syndrome (EMS) is a more recently described syndrome that shares some characteristics with PPID. Both of these disorders alter cortisol metabolism, though EMS appears to have no underlying connection to thyroid dysfunction. The pituitary gland functions normally in horses with this EMS. 

Common signs of EMS in horses include:

• Hyperglycemia
• Altered tissue-level cortisol activity
• Increased leptin concentrations
• Altered lipid metabolism with hypertriglyceridemia
• Increased expression of inflammatory cytokines
• Hypertension³

EMS is typically seen in middle-aged horses, and is more common in pony breeds, domesticated Spanish mustangs, Peruvian Pasos, Paso Finos, Andalusians, European Warmbloods, American Saddlebreds, and Morgan horses, which suggests a genetic predisposition to EMS.⁴

Diagnoses and treatments for PPID and EMS will differ, so it is important to have an experienced equine veterinarian diagnose horses suffering from the described symptoms.

Pergolide for Horses

Pergolide serves to decrease some of the hormone production by the pituitary gland. Several studies have addressed its usefulness in PPID-affected horses and shown significant improvements in hair coat, frequency of urination and drinking, frequency of infections and laminitis bouts, and many laboratory test results.³ Pergolide is a potent agonist at dopamine receptors (D1 and D2) and is 10-1000 times more potent than bromocriptine. The literature holds that pituitary pars intermedia dysfunction (PPID) in horses is a dopaminergic degenerative disease and pergolide (or dopamine) can reduce expression of proopiomelanocortin (POMC) peptides from the pars intermedia.¹

In horses, pergolide was rapidly absorbed following oral administration with plasma concentrations reaching maximum levels within 1 hour of dosing. Maximum plasma levels ranged from 1.07-3.38 nanograms/mL. Pergolide appears to be rapidly and widely distributed.¹

Pergolide appears to be well tolerated in horses. Decreased appetite is seen during the first week of therapy in ≈10% of horses treated; temporary dose reduction is often beneficial in alleviating this effect. Colic and diarrhea have been reported to occur more rarely.^1,3

Recommended dosages for horses with PPID is oral administration with a starting dose of 2 micrograms/kg once daily. This may be adjusted to effect, not to exceed 4 micrograms/kg daily.¹ Pergolide does not cure PPID however, and it can take several weeks to months to see positive results.

Where to buy Pergolide

Pergolide is available in the U.S. through several pharmaceutical manufacturers and through veterinary custom compounding companies. PERGOLIDE 0.5MG/ML ORAL SUSPENSION by NexGen Pharmaceuticals is indicated for the treatment of pituitary pars intermedia dysfunction (PPID) and endocrine diseases of older horses and ponies.

This product carries minimal potential drug interactions, however it is advisable to consult your veterinarian prior to beginning any treatment regimen.

FOR RX ONLY: A valid prescription from a licensed veterinarian is required for dispensing this medication.

¹Plumb’s Veterinary Drugs.

²Durham, A. Endocrine Disease in Aged Horses. Vet Clin North Am Equine Pract. 2016 Aug; 32(2):301-15. 

³McFarlane, D. Equine pituitary pars intermedia dysfunction. Vet Clin North Am Equine Pract. 2011 Apr; 27(1):93-113.

⁴aaep.org.