If I were you, I'd find a vet who will prescribe Clomicalm. Ametryptilene isn't approved for cats either but vets prescribe it regularly for them. Thank goodness I have an open minded vet. I have my pee cats' blood work done yearly just to be sure that there are no long lasting side effects and they've been on it for several years w/no problems whatsoever. I experienced the same thing you did w/the ruined furniture and hardwood and the ametryptilene working for only a little while. When my vet prescribed Clomicalm, it was the best thing he ever did for them and me and my house. It's certainly better than having your cat PTS. There are vets who will prescribe it. Please find one.