Actually none of the heartworm preventatives are approved for use in
ferrets.  With that said yes, Revolution was studied in ferrets and the
5-15 pound cat version is recommended for ferrets.  The Interceptor brown
0-10 pound dog is another option for ferrets.Mine will actually eat the
Interceptor.  Heartgard for cats or small dogs (0-25 pounds) is another
option.
 
The only liquid version is diluted ivomec (1ml ivomec to 9 mls propylene
glycol) given orally at 0.1ml per pound once a month.
 
Hope that helps,
Jerry Murray, DVM
[Posted in FML issue 3740]