I used Interceptor in the past til 1 of my rescue shelties turned up HW positive after taking it for 9 months. She was HW negative before that. I switched everyone to Iverhart Max (same as Heartguard) & they have all done fine. That was 6 years & 8 shelties ago. I like the Iverhart Max because it does tapes as well & in the country we do get them sometimes.
