Re: Adding Cyproheptadine to Pergolide prescription

Eleanor Kellon, VMD

---In EquineCushings@..., <jenmcgeehan@...> wrote :

I went on line and it indicated that Cyproheptadine (Periactin) doesn't seem to be anywhere near as effective compared to Pergolide. But I didn't see anything in regards to the combination.

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You didn't see anything because there is nothing there!  The suggestion came from the BI sponsored Endocrinology Group but with no formal data at all to support it.

The objection to dosages over 5 mg also comes from BI, but again with no data.  They make two general claims.

One is that horses on over 5 mg/day have more side effects but we have 51 (out of 268) horses, 19%, in the pergolide database, most for several years, with no higher reports of side effects or suspicious health problems.

The other claim is that horses that need high doses must be on low potency compounded drug.  We have roughly twice as many horses on Prascend in the low dose  categories (22% vs 10%) but 215 out of the total 268 horses are on compounded drugs.  Also, some of the high doses horses are on compounded after switching from Prascend (or Permax) because the cost was prohibitive otherwise.

If you read Prascend's New Animal Drug Application presented to the FDA

There is only formal safety data (i.e. including a control group) for dosages up to 2 mg. The adverse event reporting, which included 113 horses with no controls, only their baseline history, also only evaluated up to a 2 mg dose despite the fact that 41.6% of horses remained with abnormal lab values after 90 days on 1 mg/day and overall success rate at 180 days including horses on both 1 and 2 mg/day was 68.6%.

The suggested upper "safe" dose of 5 mg/day (it was 3 mg/day when Prascend was first introduced in the USA) is based entirely upon that being highest reported dose found in the published literature (literally just a handful of horses)- NOT on formal safety studies. It would be more accurate to state that safety of dosages above 5 (or 3) mg has not been studied.

As for the cypro, it is an old treatment with limited usefulness that was discarded long ago in favor of pergolide.  Again, there is nothing to support the idea that the combination would be more effective than pergolide alone.

Eleanor in PA

EC Co-owner

Feb 2001

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