Ivermectin among every Veterinarian I've dealt with, had been the
foremost mode of treatment against heartworms in ferrets.
Selemectin; the ingredient in Revolution ("Stronghold" abroad), in the
same manner affects the neurological system of the target parasite.
I have had ferrets treated with both products with no ill effects other
than the possibility that the patient already having been infected with
heartworms, being in risk of blockage from the dead worms.
I found this article (dated 2007)from a German study. there is a table
on page 7 that describes the dosage.
(Sorry for the long URL) [I "simplified" it. BIG]
http://www.jarvm.com/articles/Vol5Iss3/Beck%252087-96.pdf
[Posted in FML 7387]