My vet gave me Advantage for my 2 ferrets, in the following dose:
 
- 1/2 a dose of the under 9 lbs cat formula
 
And in under 12 hours, all the fleas are GONE... and my ferrets have
stopped itching and are very happy.  Plus, the stuff makes the ferrets a
sort of biological weapon against the fleas, so they are systematically
clearing out the house!!!
 
it contains the "Pytheron chemical" that is supposed to be safe from
ferrets, in all the literature I've read.
 
Get it - it seems to work wonderfully, so far!!!
 
mark.
[Posted in FML issue 2763]