Interceptor has been on maufcturers backorder for over a year. It may never come back. Earliest if ever will be summer 2013, but don't hold your breath. Milbemycin the active ingredient is in Trifexis, with a flea product, spinosad, or milbemite for ear mites. Sentinel is also on backoprder but is supposed to come back before interceptor. It is milbemycin and leufenuron(for fleas).