instructor was telling me I should have a Prix St. Georges horse, his body simply said no. Before I consulted him about Novio, David had treated
a mare for a suspensory ligament tear that would not heal. He tested her for PPID/Cushing’s and, although she came up negative, he put her on the medication for the condition any- way. Her injury fortunately healed. “I’m not an endocrinolo- gist,” he explains. “I’m just a practitioner who is frustrated by horses that should respond to treatments, but aren’t.” After my horse came up negative in the PPID test, I put him on the medication David recommended and soon was in disbelief. Within a month, symptoms that I attributed to “old horse,” “just him” and “changes in his life” disappeared. This was a horse that, I had told myself over and over again, simply couldn’t stand up to hard work. Now it appears I was mistaken. For example, the fat deposits around his tail head were
gone. His dull, not fully shed out coat was replaced by his usual healthy glow. The stall cleaner stopped beg- ging me to leave him in his turnout because he was urinating so much that his stall had to be stripped daily. I no- ticed my horse stopped urinating in the grooming area on a cement floor. (What horse pees on cement if he can avoid it?) Also, his energy returned, and I found him feeling like he was eight, not eighteen. The coat, the excessive drinking and urination, fat deposits, the slow healing and weakened con- nective tissue, which I had attributed to his age, were in fact all PPID symptoms. Yet this was a horse with “normal” results when tested for PPID.
Dr. David Eckstein and his horse “The Dude.”
Treating PPID “You have a legitimate reason to treat a horse with this medi- cation if there is some symptomology,” David says. “We have a client with a champion roping horse that was a little older and now is ridden by a 10-year-old. He was getting less ener- getic. When I saw him, I thought, he looks old all of a sudden. I tested him and he had a level of 86 pg/ml (picograms per milliliter) of ACTH (adrenocorticotropic hormone) where the top of normal is 35. I’ve put him on the medication pergolide and I’ll bet in a month she’ll be saying ‘whoa, Brownie.’” (See sidebar for more information on pergolide.) Other PPID symptoms include weight gain or weight loss,
increased hoof or tooth abscesses, laminitis, excessive sweat- ing, suppressed immune system, slow healing and slow re- covery from injury or illness, fat in the hollows above the eyes and muscle wasting, especially of topline muscles.
26 March/April 2014
“Think of it like many different types of headaches. The
wavy, thick coat that doesn’t shed is one type of headache, like someone sitting in silence, in the dark, with her eyes crossed. There are many stages prior to that,” says FEI Vet- erinarian, Technical Delegate and Chief Steward Dr. Mike Tomlinson of Thousand Oaks, California. “Maybe at most one percent of the horses I treat are classic Cushing’s and probably have a tumor. With classic Cushing’s, they will al- ways eventually die from laminitis if not treated. With PPID, we don’t know what it is. We don’t have definitive answers. We are dealing with something different than a tumor. I can tell you that 25 years ago, we didn’t put any horses on medicine and how many ponies with big wavy coats did we know when we were kids?” Today the standard tests are the dexamethasone sup-
pression test to evaluate the level of cortisol and blood test to evaluate the level to ACTH. But both can be prob- lematic. “If I suspect PPID, or as I call it ‘pergolide response disease,’ I put a horse on the medication and if he doesn’t get better, I take him off it. There are too many false posi- tives and too many false negatives, and too much inter- pretation with the standard tests used today,” says Mike. “With ‘pergolide responsive disease’ we really do not know the mechanism of action of the disease and so there can- not be a definitive test, but we know that pergolide makes them healthier.” “Once you take ACTH out of the horse, it degrades quick-
ly. It’s a very sensitive hormone,” says David. “If you leave it at room temperature or even cooled for 24 hours, you don’t get an accurate test.” Pergolide mesylate is the
medication at the forefront of PPID treatment. It is a dopa- mine receptor agonist which treats the condition (but does not cure it) by restoring dopamine to the pituitary, controlling its activity and decreasing the production of detrimental hormones. Until 2011, pergolide was a compounded drug with a poor shelf life and inconsis- tent dosage. Today Prascend is the frequently prescribed pergolide drug. Most horses react positively to the drug. Some suffer from loss of appetite and depression when they are first put on it, but do well with adjusted dosages. “I don’t know any side effects when dosed properly. I‘ve had two horses die from symptoms after I upped the tablet, but their demise wasn’t related to the drug,” says David. “One had a fatal laminitic event. He probably had a tumor.” In his practice, Mike has been able to decrease dosages
Dr. Mike Tomlinson
in several horses at certain times of the year. Some horses do better in spring and summer while laminitis incidents seem
Courtesy Mike Tomlinson
Courtesy David Eckstein
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