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  Discussion on Dexamethasone and hives
Author Message
New Member:
6harding

Posted on Wednesday, Apr 30, 2008 - 5:00 pm:

Hi. This is the second year in a row that we've been dealing with seasonal hives. Last year we did allergy testing, tried taking all foods away and slowly introducing them back, covered him in fly sheets, moved to a new barn, etc....all to no avail. The only thing that worked was dex. Then he cleared up about 6 weeks to 2 months later. Now, we're at it again. My vet doesn't want to try the pred. and hyDrOxine route because he is a show horse and we can't use the hyDrOxine and he thinks the pred. would wear off too quickly. So, how much is too much and how long is too long on the dex? I've read the articles and still don't know the answers.

Thanks, Kristen
Moderator:
DrO

Posted on Thursday, May 1, 2008 - 7:26 am:

Hello Kristen,
There are no clear cut answers to the questions of how much dexamethasone or how often is too much in the horse. In general the dexamethasone is not toxic itself though with long term use the horse needs to be monitored for Cushings disease. The most serious concern is its effects on the adrenal glands with long term use, adrenal suppression, and then discontinuation. However there are no studies that clearly indicate how sensitive the horses adrenal glands are to long time use and only one case summary published on iatrogenic Addisons that I have ever been a able to find. That horse was on frequent anabolic steroid administration for several years. For more on these conditions see Treatments and Medications for Horses » Anti-inflammatories (NSAID's, Steroids, Arthritis Rx) » Steroids, Overview of Antiinflammatory Use.

There are also many individual factors that will figure into this calculation of what is too much: the type (salt) of dexamethasone used, the dosage, the frequency, and the route of administration. Two studies suggest that .05 mg/kg of a dex solution given IV will allow the adrenal gland to recover in 4 days but repeated administration is not studied. One should note these doses are much smaller than those used for very long times in serious autoimmune diseases of horses.
DrO
New Member:
6harding

Posted on Thursday, May 1, 2008 - 10:42 am:

Thanks for your response. So am I to understand that there have NOT been reported cases of horses on dex. for 4, 6 or even 8 weeks that have had significant problems? We are trying to get as many days in between doses and the lowest dose possible that will work for our hives problem.

Thanks again,

Kristen
Moderator:
DrO

Posted on Thursday, May 1, 2008 - 7:26 pm:

None that I am aware of and I have looked.
DrO
Member:
sryder11

Posted on Sunday, May 4, 2008 - 10:42 am:

Kristen my horse was on Dex for almost 3 months between Aug and Oct last year for severe hives - you can read about it in my previous thread Hives and Dex Dosage. Even after that the hives kept recurring. The vet eventually gave him one shot of Vetalog and the hives were gone for good, at least for last season. I was nervous about giving him this but it seemed considerably more effective than all that Dex and in your case it would be out of your horse's system in two weeks or so. Maybe talk about this with your vet if the hives persist.
Member:
mcashman

Posted on Monday, Apr 4, 2011 - 11:41 pm:

Hi, Kristen!

My horse was on dex for an extended period and had no apparent ill effects at dosages sufficient to suppress some very large urticaria (a packet daily). He is now off the dex, after we found his dietary allergy this winter.

One thing that turned out to be very important was to very, very slowly taper him off the dex. Apparently the dex suppresses the horse's natural corticosteroids, so a decrease in dose caused a smaller or larger set of hives in reaction to any remaining allergens in his system / environment. After 12-24 hours, his system would catch up as long as I left him at the new lower dose. I maintained each decrease for about a week before going down again and spent over a month before going to every other day on a very very small dose.

I hope this helps!
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