We had a 12year old West highland white Terrier in perfect health, she was taking Nexguard and Heartguard since she was a puppy, no problems at all, a month ago our veterinarian staff suggested we change her over to Simparica because it is just one pill instead of two, so we did, a month later she started having convulsions and seizures and Died, She died because of this crap, I tried CPR, Nothing. User's recommendation: DO NOT USE THIS STUFF! I lost my little Girl.