Benedryl is a fairly "safe" drug.  The dosages I listed previously for
pre-medication (0.5cc up to 2 lbs, 0.75cc 2-4 lbs, 1.0cc over 4 lbs) is
a relatively "light" dosage.  I give this dosage once a day for 5 days
before vaccination to help their system "build up" an antihistamine
"buffer".  (I'm not a vet so the terminology often escapes me, so I'll
just try for an analogy to explain it.)
 
As Joanne D'Amico noted, considerably larger dosages are perfectly safe.
If only one dose is given before a vaccination, the larger dose would be
well within reason.  In fact, when we merely suspect a ferret might be
starting to have a reaction, I give a double dosage, and if the symptoms
(usually nausea) do not lessen within 10 minutes, I give that dosage
again, and if even a portion of that is vomited, I give that doubled
dosage yet a third time (on the way to the vet).  The following year that
ferret's pre-treatment dosage is doubled and it is vaccinated at the
vet's office following the 5 day pre-treatment with an additional steroid
injection by the vet before the vaccination with life-support equipment
on stand by.
 
We had several close calls before switching to the Purevax vaccine, but
none that have required life-support equipment since.  Our worst reaction
to Purevax has been slight nausea and diarrhea.  As far as numbers go, we
expected a minimum 10% to react, with 2% of that 10% being serious, if
not critical threats on Fervac-D.  With Purevax, the percentage of
reactions is less than 1%... this is just the numbers we've observed with
the ferrets here, I have no idea how the numbers go on a larger scale,
nor the numbers on the dog vaccines that some vets use for ferrets.
 
We still vaccinate ferrets that had life-threatening reactions
previously, using the precautions listed above.  To date the most serious
reaction has been mild nausea (pawing at the mouth, rubbing chin on
carrier floor), to which the vet immediately responded with an additional
steroid injection.
 
Canine distemper is ugly and as easy to spread as walking across the
yard.
 
Debi Christy
Ferrets First Foster Home
www.ferrets1st.com
[Posted in FML issue 5005]