When the Vitamin A toxicity discussion arose, I decided that I'd like Dr.
Kemmerer's opinion. This is her response to my query if Vitamin A could be
toxic and therefore, Ferretone:
 
I checked my own references, called two poison hotlines, and I'm waiting for
a return call from Tom Willard.  There is no LD 50 established for vitamin A
(Lethal Dose 50 is the dosage at which 50% of the animals dosed die; this is
the gold standard for judging toxicity levels), and toxicosis is more
theoretical than real.  A very few cases have been documented for acute
poisoning, and these were cases where the animal or person ingested huge
amounts of raw polar bear liver, which has the highest concentration of
vitamin A on the planet.  There have been a FEW cases of chronic toxicity in
children, but this requires extremely high doses for a period of many weeks
to even produce noticeable symptoms.  The first symptom is usually diarrhea,
followed by nausea.
 
Toxic doses in dogs and cats are quite different, but either one requires
extreme doses.  In dogs the toxic dose is about 3000 IU per KG body weight
daily for a minimum of three weeks to produce any clinical signs.  In cats,
the toxic dose is 10,000 IU per kg.  Even going with the lower of the two,
the average one kg ferret would need to ingest 12 cc's of ferretone daily
for a minimum of three weeks just to get diarrhea or nausea.  The one-time
acutely toxic dose is generally considered to be about ten times the chronic
dose.  In addition, absorption of excess vitamin A is counteracted by
vitamin E, which is also in ferretone, so that would tend to increase the
amount needed for toxicity.  I'm hoping Dr. Willard knows the toxic dose
specific for ferrets--he's out of town, due back Wednesday.
 
Where does this stuff come from? The poor Ferretone people are probably
getting inundated with complaints, and have no idea why. I don't either. I
can't find any reference to an actual case of vitamin A toxicosis in an
animal in the last ten years (other than experimental).
 
[Later]
 
I spoke with Dr. Tom Willard from Totally Ferret today. He's not aware
of any studies or knowledge about vitamin A that is specific for ferrets. He
did reinforce my assertions about what the toxic levels may be (extremely
large amounts), and mentioned that he did see a recent study in cats where
cats were fed 40,000 IU's of vitamin A daily for a period of weeks to
months, and the researchers were not able to produce signs of toxicity. We
both agree that you may quote us in anything you'd like to post on the FML
on this issue. He did say that each ounce of Totally Ferret (about one day's
intake for an average size ferret) contains 650 IU's of vitamin A. That's
the equivalent of 2 1/2 cc's of Ferretone.
 
I spoke with Dr. Hopkins today. He said he'd email you some more info on
syringomeylia--If there's any discrepancies between what I said and what he
says, go with what he says. He's the expert.
 
I haven't heard from Dr Hopkins yet so I don't have any more info....
 
Susie, Ken & Eric Sherman
Trixie, Binky, Kodi, & Rascal
 
Desperately missing Casper,
rest in peace, sweet angel
 
September 1, 1993 to February 21, 1997
[Posted in FML issue 1878]