In clarification, the truth is that to date there is no KNOWN toxicity
due to overdoses of the water soluble vitamins, which are vitamin C and
the B complex vitamins.
You are correct that a dehydrated horse in the middle of a race certainly
would have decreased glomerular filtration rate, and therefore decreased
clearance of these vitamins.
The human RDA of vitamin C is 60mg/day. People routinely consume
1 gram/day with no adverse effects. That's 17 times the RDA. I have
even known individuals who want to "cure their cold" who consumed 2-3
grams per day. The most common side effect from these doses is an upset
stomach, and altered pH of the urine ( which in turn could alter the
clearance of other renally excreted drugs).
As for the B complex vitamins, reported adverse side effects are related
to the route of administration. IV administration can result in
anaphylactic allergic reactions. IM injection can also result in local
irritation or local allergic reactions. The other side effects, specific to
niacin, is dilation of the small blood vessels of the skin with a
tingling, itching sensation.
It is conceivable, that if someone administered 100 times the RDA other
more serious side effects could result. You are correct in pointing out
my own examples that even water and oxygen have the potential to be
toxic. Especially if a horse was dehydrated this could pose a serious
problem. The difference between the toxicities of these vitamins versus
the fat soluble vitamins (Vits. A,D,E, and K) is that as soon as the
animal is rehydrated he should begin to eliminate the water soluble
vitamins. In comparison, the fat soluble vitamins are stored in the body
and lead to Irreversible toxicities.
One of the problems is defining the term "megadose". This is a vague
word that does not have a true definition. Is 2x normal a "mega"dose?
I'm afraid this is a current issue in medicine that remains to be resolved.
There probably are people who may believe that administering large doses
of vitamins (especially with the focus on antioxidants) will benefit
their animals, or possibly even themselves. I never meant to give the
impression that this could "do no harm" and I am posting my reply to you
through the discussion group to make that point. There is always a
potential danger from overdosing on ANYTHING. Medical science may just
not know yet what that danger is.
Doses and RDA (recommended daily allowance) are published as guidelines
for the safety of the consumer. I guess because I have studied drugs
and I do adhere to dosing guidelines I find it difficult at times to
understand why someone who is not trained would want to exceed those
guidelines and risk any harm to their animals or themselves.
Thank you for you interest!
Sincerely,
Lynn Crespo
Davie, FL
Lynn M. Crespo, Ph.D.
Associate Professor and Chair
Department of Pharmacology
Nova-Southeastern University
lynn@alpha.acast.nova.edu
---------- Forwarded message ----------
Date: 27 Jul 1995 00:09:10 -0600
From: Meyer Greg <gmeyer@cvmmdl2.msstate.edu>
To: "LYNN M. Crespo" <lynn@alpha.acast.nova.edu>
Subject: RE: AERC Drug Policy
Dr. Crespo,
Please clarify this for me,
>It is impossible to overdose on the water soluble vitamins
>as any excess that the body does not need will be excreted in the urine.
It is my understanding that it is possible to O.D. on water soluble vitamins.
Do not the vitamins have to be absorbed into the blood in order to be removed
by the kidney and placed into the urine? Would not the potential toxicity be
related to the amount administered per unit of time, and the route of
administration (oral, IM ect...) and also be tied into the hydration status
of the animal?
e.g. a dehydrated animal will tend to be conserving water and thus not
producing much urine (lower glomerular filteration rate) and thus not be
possibly able to rid its body of excess water soluble substances until
rehydrated?
As I have been taught, anything in enough excess is toxic. Oxygen and water
are both good examples. The question in my mind is just what constitutes a
"mega dose". I have seen many good intentioned people armed with a little
knowledge do very dangerous things. I am worried that saying that something
is impossible (like its impossible to OD with a water soluble vitamin) may
give the wrong impression, and result in injury.
Respectfully,
Greg Meyer
Mississippi State University
College of Veterinary Medicine
gmeyer@cvmmdl2msstate.edu
_______________________________________________________________________________
From: LYNN M. Crespo on Wed, Jul 26, 1995 10:36 PM
Subject: AERC Drug Policy
To: endurance@moscow.com
I have been reading with great interest the discussion regarding the AERC
drug policy and the dilemma as to how to define a drug. For the purpose
of furthering the discussion I would like to offer a Pharmacologist's
point of view.
In the fields of medicine and pharmacology a drug is defined as:
Any substance that in SMALL quantities alters the body's physiological or
biochemical response.
The Father of Pharmacology was Paracelsus who in 1583 wrote:
"All things are drugs (poisons), for anything in excess will change
(poison) the body.
>From this perspective some of the previous discussion points out the
dilemma in defining a drug. Oxygen (in excess) when administered to a
creature (be it human or equine) will alleviate breathing difficulties,
speed recovery, or if not needed, make us dizzy and giddy. Water, in
excess will dilute the blood stream and can lead to a syndrome known as
water intoxication causing such severe problems as seizures.
Vaccinations which we administer to ourselves and our animals to alter
the immune system with the purpose of preventing infections are also
considered drugs. Yet who would consider keeping their animals without
the use of these drugs. They are an essential preventative health care
measure. I feel that the periodic use of Adequan to prevent permanent
joint damage also falls into this category. Adequan will not mask a
serious problem as it has no antiinflammatory properties. Perhaps the
AERC should consider a time limit, such as can not be administered
withing 1 week prior to the race, this would still allow the preventative
health care usage, but eliminate the possibility of it altering the
outcome of the ride.
As to the use of vitamins. Vitamins will not create superathletes, nor
will they significantly alter performance, unless the animal is in
deficit. Vitamins fall into 2 categories, water soluble and fat
soluble. It is impossible to overdose on the water soluble vitamins
as any excess that the body does not need will be excreted in the urine.
Megadoses of the fat soluble vitamins usually lead to the development of
significant toxicities including irreversible liver damage and
neurological damage. So the use of megadoses only defeats the purpose.
For the safety of the horses the AERC is wise to not permit the use of
megadose vitamins as most people do not know which are water soluble and
which are fat soluble.
Hope this is food for thought for riders and directors.
Lynn
Davie, FL
Lynn M. Crespo, Ph.D.
Associate Professor and Chair
Department of Pharmacology
Nova-Southeastern University
L. M. Crespo
lynn@alpha.acast.nova.edu