I use Interceptor on all 3 of mine (2 adults & 1 pup). The med in Interceptor is Milbemycin. Heartgard Plus is the one with Ivermectin…known to cause seizures in some breeds (collies, whippets, some others).
In Maine I only use it from April - October (and do blood tests yearly in the spring) - mosquitoes don't like our winters so I don't like to give the kids meds they don't need.
All 3 of mine take it as though it is a treat...usually I ask for a sit for it.