I use Ivomectrian on my GP's, German Shepherd and even my Dalmatian. Never had a problem, Dal lived to 13, others are still with me. Use it on my chickens and other critters too.
My White German Shepherd gets it too and never had a problem, as well as all my GP's. So basically if your vet doesn't give your dog Heart guard but makes you use...Interceptor, I think it's called, then you wouldn't want to use Ivermectian.