My father was diagnosed is Parkinson's disease about 7 years ago and came to live with my family, so I could take care of him, and he brought his Golden Retriever. My father died a year later, but we kept the Golden with us. He is now 16 1/2 and has been the best pet we could have ever asked for. He has been on Phycox for his joints for the past year and a half and has been doing well. He started having what we thought were seizures about 2 months ago, and the vet said he had tachycardia. He said he wasn't in any pain, and seemed in great health otherwise. Actually, the vet was very surprised his tail still worked and was still able to get on our couch...In the last day or two, he has been falling down. If he stands still for a minute, he starts shaking and his back legs go out from under him. If he's on carpeting, he can get right back up, but on tile or vinyl, he has a hard time getting back up. He is eating more than normal, and still going out, when he has to. But it seems he has almost reverted back to puppyhood, as he has gotten in the garbage (which he has never done), eating the cat food, again, which he has never done. He has even eaten kitty litter. I don't want him in pain, I don't want him to suffer just because we don't want to let go. How do we know when it is time?