Lisa,
I'm so sorry to hear about your loss. Yes, those flea medications can be hard on older dogs. Our Pomeranian had a seizure once just after I put a new flea collar on her. That was my fault, though, since I'd just given her a bath with flea shampoo too, and the combination probably was too much for a small and very elderly dog.
I stopped using flea collars on her after that, and she did recover and remained healthy for quite a while longer. I began feeding her the Missing Link's joint supplement for elderly dogs, which seemed to help her coat and her general health a lot too. There are some recommendations on how to report problems with Bravecto at the following link:
https://www.fda.gov/animal-vet...
