Basic Pergolide Information
Pergolide is a human drug used in the treatment of Parkinson's disease. Pergolide is the drug of choice for the treatment of pituitary pars intermedia hyperplasia or Equine Cushing's Syndrome (ECS) in horses. Pergolide works by binding with drug receptors in the brain that control the production of dopamine.
Cyproheptadine is another drug that has been used in the treatment of ECS although recent work indicates that it is not very effective, and that pergolide is clearly the treatment of choice.
Pergolide for Horses
For many years, pituitary pars intermedia hyperplasia was called pituitary adenoma. In most cases, this commonly seen condition of older horses and ponies is caused by hyperplasia or hypertrophy of the pars intermedia rather than tumor. Although the hyperplasia may eventually progress to adenoma formation, that is considerably less common. The average age of horses diagnosed with ECS is 20 (range 7-42). Ponies may be more commonly affected. Pituitary pars intermedia hyperplasia is a medical problem that is managed, not cured. Animals that are being treated are usually on medication for the rest of their lives.
Clinical signs associated with ECS include hirsutism, polyuria, polydypsia, abnormal fat deposition, abnormal sweating patterns, laminitis and decreased immune competence. Horses are usually started on a low dose of pergolide (0.5 mg/day) and re-evaluated by 6 weeks. If there is no improvement, the dose should be gradually increased (by 0.25 mg) until improvement is seen. Recent work reported by J. Beech at the 2003 AAEP suggested that some horses may require higher doses than those that are commonly used.
A possible differential diagnosis for ECS is the recently hypothesized Peripheral Cushing's Syndrome (PCS). PCS is thought to be a different endocrine disturbance although there are some similar symptoms. Horses with PCS are overweight with cresty necks, abnormal fat distribution and frequently suffer from laminitis. They are not hirsute, and do not respond to pergolide.
Pergolide Side Effects
• Decreased appetite during the first week of treatment is the most commonly reported side effect of Pergolide. This may be managed by an initial reduced dose followed by a gradual increase.
• A number of side effects are listed in humans taking pergolide with other medication for Parkinson's disease. Side effects included low blood pressure, headache, GI upset, anemia, respiratory infections, dizziness, and hallucinations.
Pergolide Precautions
• It is important to identify and use the lowest possible dose of pergolide. Based on information from human Parkinson's disease patients, there is some thought that this condition may, over time, become resistant to medication.
• High doses of pergolide have been tested in laboratory animals without causing detectable harm to the fetus but this work has not been done in horses. It is not known if pergolide is excreted in milk but this type of drug may interfere with lactation. No information was found on pergolide use in breeding stallions. Pergolide should only be used in pregnant or lactating animals if the benefits outweigh the risks.
Pergolide Drug Interactions
• Phenothiazine tranquilizers such as acepromazine may interfere with the action of pergolide.
Pergolide Overdose
• Overdose in humans causes gastrointestinal upset and hallucinations.
More Peroglide information:
http://www.pergolidealert.com/