Tying up and Drugs in Canada

Patricia Dowling DVM (dowling@sask.usask.ca)
Tue, 17 Dec 1996 09:07:24 -0800 (PST)

Tom:
Endurance horses do "tie up" different than racehorses.
Rhabdomyolysis in long distance horses is initiated by poor
blood flow to the large muscle groups. High body
temperatures cause shunting of blood away from muscles to
the skin for cooling. (The average endurance horse produces
enough heat in an hour to bring 25 gallons of water from
room temperature to a boil). They also lose about 12
liters/hr as sweat. Potassium lost in sweat is 10-20 times
its concentration in the plasma. Low plasma potassium and
increases in cortisol from stress cause constriction of
blood vessels in muscle. From poor blood flow, the lack of
oxygen in muscle interferes with the contraction-relaxation
of muscle fibers and anaerobic metabolism in the muscle
cells produces lactic acid. Despite the local acidosis in
the oxygen-starved muscle, in distance horses the overall
systemic balance is still a metabolic alkalosis because of
the chloride loss (in sweat) and bicarbonate conservation
(by the kidney in order to maintain the electical balance
with the positive sodium ions which are not lost in the same
proportion as the chloride).

Rather different than the TB and QH fillies that I've seen
tie up in their stalls at the track!

By the way, Tom, I first heard you lecture as an
undergraduate student at Texas A&M in about 1980, I enjoyed
it then and am enjoying your participation on this list.

I mostly lurk, as I have a busy teaching schedule. However,
as an American teaching at a Canadian veterinary school, I'd
like to point out to the list that the Canadians have been
very quiet on this whole discussion of drugs and
nutriceuticals. (For the person interested in credentials,
I'm board certified in large animal internal medicine and
clinical pharmacology and am the Canadian representative on
the United States Pharmacopeia). Anyway, the Canadians are
quiet, because unlike the FDA, the Bureau of Veterinary
Drugs in Canada does not recognize "nutriceuticals". These
products are not allowed in Canada - unless the
manufacturers will meet the requirements of a "drug". Ie,
Cosequin was sold in Canada for a short time, until the BVD
heard about it, and kicked it back out of the country.
Adequan and Cartrophen are available, because they've met
the standards as a drug. So unless they smuggle them across
the border, Canadians compete without these products and
they sure seem to do ok to me. It'd be interesting to hear
from other foreign riders if these products are available in
Great Britian and Europe as well.

I won't enter the debate on whether nutriceuticals work or
not; I'm waiting for more scientific evidence personally.
But one point I'd like to make to the horse owners is the
difference between a real "drug" and a "nutriceutical": real
drugs must meet standards of purity, quality control, etc.
As consumers, you don't have much of a guarrantee of purity,
efficacy, safety, etc. for the nutriceuticals, other than
the manufacturers' promises. The composition of these
products vary widely. As expensive to use as they are, I
think you, the consumer have a right to expect some kind of
quality standard. There is a movement in the industry, lead
by the Nutramax folks, to set standards for purity and
composition, but it hasn't happened yet. Nutriceuticals are
not always harmless. There's a rather famous report on a
tryptophan supplement that was imported from Japan and sold
in health food stores in the US. The product was
contaminated and was killing people, but it took awhile to
figure out the link between the deaths was a certain brand
of tryptophan.

Gwen: I haven't forgotten, I just haven't made it to the
library yet. Once I get my finals graded...

Merry Christmas.

Trisha Dowling, DVM, MS
Diplomate, ACVIM & ACVCP
Associate Professor, Veterinary Clinical Pharmacology
Western College of Veterinary Medicine
Saskatoon, SK