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]