What is Pergolide?
Pergolide (pergolide mesylate) controls the output of a hormone called ACTH. If ACTH is not controlled, the pituitary tumor grows unchecked. To obtain pergolide you need a prescription from your vet, which he or she should give once blood tests confirm high ACTH levels. [i] [ii] [iii] Once a horse is diagnosed with PPID, he will be on pergolide for the rest of his life. Normally pergolide should never be administered to a horse with normal ACTH blood levels. However, no PPID test is perfect and with a difficult to control laminitis case, your veterinarian may decide a trial of pergolide is warranted.
Once you have a prescription in your hand, you can obtain pergolide from many sources. Pergolide used to be very expensive and even today if cost is a concern, you may want to compare prices at different compounding pharmacies. There is a list of compounding pharmacies compiled by group members, in the Database section of the ECIR Group. (See Links section below)
There are several formulations for pergolide available: liquid, loose powder and capsules. Some vets are not aware that pergolide formulation is vitally important to the shelf life of the drug. There is no benefit to the horse or cost saving if the drug is inert. Save yourself time, money and grief by insisting on a prescription for the formulation that best suits your needs. In general, encapsulated pergolide powder is the most economical and stable.
Preliminary data suggests pergolide will be more stable if kept refrigerated. [vi] [vii] [viii] However, care should be taken to make sure the container is tightly sealed since high moisture in refrigerator air could compromise stability. Some members keep long time supply, in a double container and put a week or two’s worth of capsules in a smaller container. Freezing will greatly reduce the potency of your pergolide so in winter if it is being delivered by courier or mail, be sure to watch for the delivery person. If possible, ask your pharmacy to request a signature upon delivery.
“The only "correct" dose of pergolide is the one that controls his ACTH.”
- Dr. Kellon, ECIR Message #132610, Sep 2, 2009.
Each horse is an individual. Some are laminitic with almost normal ACTH levels. Others can have an ACTH level hundreds of units higher than lab normal ranges but are not showing laminitis. On the other hand, for some laminitis is the first physical symptom. Horses are normally started between 0.5 and 1.0 mg and most use 1.0 mg for a full sized horse. However, many horses, especially advanced cases, require more pergolide - up to and possibly beyond 17mg[ix] [x] [xi] [xii]. There are two ways to determine if your pergolide dose is correct. One is by careful monitoring of the horse’s physical symptoms. The other, more accurate and more costly method, is by monitoring the level of the hormone ACTH with blood tests. Whichever manner or combination of the two used, you should closely monitor physical symptoms and whenever you see an increase in physical symptoms consult with your veterinarian about dosage adjustments.
How to Use ACTH Blood Tests to Determine Dosage
PPID horses taken off pergolide exhibit a return of symptoms after 2-4 four weeks, so it is recommended to wait 2-4 weeks once a target dosage has been reached to either re-evaluate physical symptoms or run an ACTH test.
How to Monitor Physical Symptoms to Determine Dosage
Though not as accurate as blood tests, for various reasons, costs not being the least, some ECIR Group members choose to monitor physical symptoms to determine dosage. Careful daily observation is needed. This may be difficult for owners who board or who are not involved in the day-to-day care of the horse. It is vital that owners know all the symptoms of both PPID and Insulin Resistance because out of control PPID causes Insulin Resistance (IR).
Symptom monitoring is subjective. Words like large, small, excessive etc. mean different things to different people. For a really great way of tracking changes in your horse’s symptoms please see ECIR Message # 111988 .
It is important, though not essential, to know what is normal for your horse. For example owners sometimes monitor their horses without being able to discern any difference in symptoms because the dosage might be high enough to prevent laminitis, but not enough to bring about a change in physical symptoms. ACTH testing is really the most reliable way of making sure you are controlling your horse’s PPID.
ACTH Testing and Seasonal Influences
ACTH, in all horses, normally and naturally rises in autumn and drops in spring. PPID is confirmed when the ACTH stays high year round, but in less advanced cases of PPID the ACTH may only be out of normal during the fall. These seasonal influences can lead to a mistrust of autumnal test results when making a diagnosis. However, at any time of year, a high ACTH puts your horse at risk of developing IR and IR means your horse is at risk to of laminitis and founder. When running ACTH tests to monitor dosage, there are no “false” highs, especially when preventing laminitis is the goal and fall is a time when many horses get laminitis.
ACTH tests can be run to check pergolide dosage at any time of the year. To prevent seasonal influences from skewing your ACTH test results, blood should be drawn and tested at the same time of the month as previous years. With the higher threat of laminitis between August and December, and to keep veterinary costs down, at a minimum dosage check ACTH tests should run in early July, again in September and anytime an increase in physical symptoms is noticed.
There are basically two different temporary but common side effects that are caused by pergolide: depression and lack of appetite. This is known in the ECIR group as the “pergolide veil”. When first starting pergolide, or when dosage is increased or decreased too quickly some horses become lethargic and uninterested in food. Tapering the change in dosage is the best defense against side effects. When properly tapered, the ECIR Group horses have had either no pergolide veil and feel better right away or the veil symptoms resolve quickly – within two weeks.
Pergolide veil can be very distressing to owners. It is often the case that horses starting pergolide are also starting a new, safer and less “yummier” diet. The horse certainly appears to dislike the new food but it really is just the veil making him less inclined to eat. Hang in there – they do get over this stage. Once the horse gets used to being on pergolide, he will start to eat normally again and suddenly will start to enjoy the “yucky” food.
Meanwhile, there are a few things you can do to help your horse adjust. Tempt the horse to eat with different flavorings (see links section). If tapering and flavorings fail, adaptogens can help.
Adaptogens are natural substances that help the body block negative responses to chronic stress. A formulation of liquid extract of adaptogenic herbs that has a good track record in the ECIR group is APF. A less expensive adaptogen is Canadian, American or North American ginseng (Panax quinquefolius). Some ginsengs cause elevated insulin so be sure the Latin name is correct.
Whether increasing or decreasing dosage or just starting pergolide for the first time taper at a rate of .25 mg every three days. Ordering a supply of 0.25 mg capsules makes tapering easier.
How to Get Them to Eat It?
Many horses, especially those who don’t like medicines are as good as airport “sniffer” dogs at detecting drugs hidden in feed. During the pergolide veil many horses will not take anything slightly suspicious. Try mixing the pergolide with water or plain yogurt and promptly syringing it into their mouths. Safe treats often can be used to hide the pergolide, try a prune, a single large grape or a section of cored out carrot. Some members resort to less safe treats which can be dangerous if your horse is border-line laminitic so if you feel you have to go that route, use as little of an unsafe treat as possible. Some members put pergolide powder on wet beet pulp. The drawback to this method is that sometimes horses dribble food – especially if not being fed by hand – making it impossible to tell if the horse ingested the full dose.
The secret to success at medicine time is relaxation, perseverance and using a carrier (treat) that works for your horse and you. Try to think of “medicine time” as “treat time” instead. Expect and plan for spit outs. Stay calm; don’t let the horse know this is a “bad” thing. Just pick up the cap and try again and again until it goes down. If you get upset he’ll get worried and it will only increase his mistrust and slow down the process.
Make things easier for yourself by giving the “treat” in a location which it is easy to spot and retrieve the ejected white capsule. Extra treats fed as a “chaser” just after the capsule has gone in the horse’s mouth often stops spit outs. It will take a little time and extra treats but eventually he’ll come around.
Acepromazine is a dopamine antagonist so it counteracts pergolide. A single dose for a veterinary procedure isn't a big issue, but it may be a consideration if the vet puts a horse on ace several times a day as a vasodilator for laminitis. This is a judgment call for the vet.
Links to more information:
Communicating with your Vet – to access this article, you must first register on TheHorse.com (free), then enter article 273 in article quick find.
Pergolide Dosing Tips - ECIR Group Message #135684
Pergolide Dosage Database – A listing of ECIR horses’ pergolide dosages
Pergolide Facts - ECIR message # 135349
Pituitary Pars Intermedia Dysfunction/Cushing’s Disease - List of physical symptoms
Vet Refuses To Write a Prescription? - Srcroll down to “Vet Refuses”
Below is a list of documents in the ECIR Group Files. Only links to folders work so you will have to scroll down to find and open the actual document.
New Member Primer - lists physical symptoms
ECIR Group Inc. and Dr. Eleanor Kellon, VMD © 2009
[vii] Comparison of Pharmaceutical Equivalence for Compounded Preparations of Pergolide Mesylate - Scott D. Stanley, PhD; and Heather DiMaio Knych, DVM, PhD