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]