Pergolide mesylate (Prascend®) is a medication used to treat horses with pituitary pars intermedia dysfunction (PPID), previously referred to as Equine Cushing’s disease.

This common endocrine disorder, typically observed in older horses, can cause tendon and ligament breakdown, abdominal wall weakness, tooth loosening, depressed immune function, altered temperature regulation, increased coat length, poor shedding, and insulin resistance with laminitis.

It is estimated that between 20 and 30% of horses and ponies develop PPID by the time they are 20 years old. PPID is progressive and neurodegenerative, resulting in serious complications without proper management. [1]

While there is no known cure for PPID, its symptoms can be managed with medication and proper care. According to research, 75 – 100% of horses with PPID that are treated with pergolide experience an improvement in symptoms. [2][3]

Prascend® is the only FDA-approved treatment for horses with PPID. [1][4] If your horse has been diagnosed PPID, consult with your veterinarian to determine if Prascend® is appropriate treatment.

Pergolide Mesylate (Prascend®) for Horses

Prascend® is a brand name for the medication pergolide mesylate, manufactured by Boehringer Ingelheim Vetmedica. It is available in tablet form and is administered orally to horses with Pituitary Pars Intermedia Dysfunction (PPID) .

Pergolide mesylate is derived from ergotamine, a natural compound present in the ergot fungus (Claviceps purpurea). This drug acts as a dopamine agonist, binding to receptors on neurons and increasing dopaminergic activity in the brain. [5]

By mimicking the effects of dopamine, pergolide counteracts some of the effects of PPID and inhibits the excessive release of adrenocorticotropic hormone (ACTH), beta-endorphin and melanocyte stimulating hormone as well as their intermediates. This can minimize symptoms and slow disease progression. [1]

Clinical trials show that pergolide promotes normal hair growth and alleviates muscle wasting in affected horses. This drug also helps to increase energy levels and improves body condition in horses with PPID. [6]

Prascend pergolide mesylate tablets for horses

Pergolide for Horses with PPID

Pergolide offers significant benefits in managing horses with PPID and improving their well-being.

PPID occurs due to the gradual loss of dopaminergic neurons in the hypothalamus of the brain, leading to a decline in dopamine production. The precise cause of the oxidative stress behind this degeneration is unknown.

PPID Pathophysiology

Dopamine plays important roles in the central nervous system and is involved in regulating hormone levels. [7] Specifically, dopamine regulates the release of ACTH and other hormones from the intermediate lobe of the pituitary. [4] ACTH is normally produced in the anterior pituitary where it’s release is inhibited by high levels of cortisol in the blood.

In horses with PPID, a lack of dopamine disrupts regulation of ACTH. As a result, the pituitary gland overproduces ACTH, which then stimulates the adrenal glands to produce excessive amounts of cortisol. [4]

Cortisol is a stress hormone that affects various body systems and contributes to the characteristic clinical signs observed in horses with PPID.

PPID Symptoms

Understanding the signs and symptoms of PPID is crucial for timely detection and effective management.

This complex hormonal disorder can manifest in various ways, with common symptoms including: [3][4]

  • Hirsutism – excessive & abnormal hair growth, typically presenting as a long, curly coat
  • Delayed shedding
  • Pot belly
  • Weight loss
  • Muscle wasting & loss of topline
  • Excessive thirst and urination
  • Compromised immune function leading to frequent infections
  • Excessive sweating
  • Sinusitis
  • Tooth loosening
  • Frequent infections (often oral, pulmonary or dermal)
  • Tendon and ligament weakening

Laminitis, also known as founder, is a condition that can develop secondary to PPID. This painful inflammatory condition is characterized by damage to the laminae of the hoof.

Repeated laminitis episodes can lead to severe lameness over time.

Diagnosis

PPID is typically diagnosed by physical examination and specific diagnostic tests. Early signs may be a first-in-lifetime laminitis in the fall or unexplained tendon and ligament problems.

The classical clinical signs of excessive, curly hair growth and delayed shedding, can indicate PPID but these are seen in advanced disease.

Although there is no single test that can offer a definitive diagnosis for PPID, common diagnostic procedures include a thyrotropin-releasing hormone (TRH) response test and measurements of basal plasma ACTH concentration. These tests help evaluate hormone levels and provide valuable insights into the presence of PPID. [4][14]

Despite increased cortisol production, plasma cortisol levels may or may not be elevated in horses with PPID. Removal of cortisol from the blood may also be affected. Therefore, plasma cortisol levels are not typically used for diagnosis of PPID. [8]

Pergolide Benefits

Pergolide acts as a dopamine D2 receptor agonist, compensating for the impaired dopamine signaling seen in horses with PPID. [5]

This activation of dopamine receptors inhibits the excessive release of ACTH from the pituitary gland. Through the suppression of ACTH release, pergolide improves regulation of cortisol production and better overall hormonal balance. [3]

Treatment with pergolide shows significant clinical benefits in horses with PPID, with one study reporting a 76.1% success rate in PPID horses. [9] Pergolide has also been found to return ACTH concentrations to normal levels in 28 – 74% of cases. [2]

Based on unpublished data by the ECIR group, administration at doses considerably above the recommended level is often needed to control the disease.

Researchers also report improvements in the following clinical signs within 3 – 6 months of beginning treatment: [9]

  • Hirsutism (excessive hair growth)
  • Polyuria (frequent urination)
  • Polydipsia (excessive thirst)
  • Delayed shedding
  • Abnormal fat distribution
  • Muscle wasting
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Dosage & Administration

Seek guidance from a veterinarian before administering any medications, including pergolide, to your horse. Your veterinarian will be able to determine the appropriate dosage and provide specific instructions based on your horse’s condition and body weight.

Before starting pergolide treatment, your veterinarian will assess your horse’s baseline endocrine values, including basal ACTH levels. This establishes a starting point for treatment and allows veterinarians and horse owners to monitor the horse’s progress throughout the treatment period.

Pergolide is administered orally either by placing the tablet directly i