South African Equine Veterinary Association Congress 2015 Protea Hotel Stellenbosch
Current treatment recommendations: At present, it is the author‟s recommendation that the initial
medical treatment for equids with PPID should be pergolide at a dose of 2 μg/kg, PO, q 24 hours
(1 mg/day for a 500 kg horse). If no improvement is noted within 30 days (depending on season
as hair coat changes will vary with the time of year that treatment is initiated), the daily dose can
be increased by 1-2 μg/kg (to 1.5-2 mg/day for a 500 kg horse) with reassessment after 30 days.
The author typically increases pergolide to a total dose of 6 μg/kg (3 mg/day for a 500 kg horse).
If only a limited response is observed at this dose of pergolide and endocrine test results remain
abnormal, addition of cyproheptadine (0.5 mg/kg, PO, q 24 hours) to pergolide therapy has been
effective in a limited number of cases treated by the author.
It is important to recognize that the rate of clinical improvement is higher than that for
normalization of endocrine test results. For example, in a treatment study performed by the
author, 13 of 20 pergolide treated horses were reported to have improved clinically while only
seven of 20 had normalization of endocrine test results. Thus, it is prudent to regularly measure
blood glucose concentration and perform follow-up endocrine testing when managing equids with
PPID. The author currently recommends measuring plasma ACTH concentration or performing
an ODST at least yearly (between December and June in horses in the northern hemisphere) in
horses that appear to be stable and 30 days after a change in medication dose or addition of
cyproheptadine.
Prognosis: Once present, PPID is a lifelong condition. Thus, the prognosis for correction of the
disorder is poor. However, PPID can be effectively treated with a combination of management
changes and medications. Thus, the prognosis for life is guarded to fair. Following the Michigan
State University cohort of horses described above, survival after 3 years of treatment with
pergolide was 78% declining to 40% after 5 years. Finally, the author has followed a couple of
horses treated with pergolide for nearly a decade and has become convinced that the drug
improves the quality of life but that does not necessarily equate to prolonging life.
Challenges in treatment recommendations: Greater recognition of the prevalence and variable
clinical syndromes of PPID, better understanding of endocrine tests, and FDA approval of
PrascendTM for treatment of PPID have been major advances in our ability to manage PPID.
Nevertheless, challenges remain for clinicians working with PPID-affected equids and
researchers investigating the disease.
For clinicians, current endocrine tests have a limited ability to provide supportive evidence for
“early” PPID when clinical complaints and signs are nonspecific. Consequently, a decision for
starting medical treatment with pergolide often relies on clinical experience and judgment, rather
than conclusive test r \