Anyone here experience something similar in long-term pergolide use? 30 year old crossbred gelding (Anglo-Arab?) diagnosed three years ago with PPID, no EMS, on Prascend continually since. Labs done every six months and haven’t changed much if at all. He is becoming extremely anxious and is showing increasing aggressiveness now toward people. Both treating vets say he is not blind and does not seem to have impaired vision but his anxiety is off the meter. For example, though we live where it snows every winter, this winter he has become utterly terrified of the snow. He has always been a bully toward other horses so he gets turnout by himself where he can see and visit but not bite. But now is showing aggressiveness toward people - pinning ears, whirling - not biting, not kicking, but threatening. Vets say Prascend does not cause anxiety or aggressiveness. I’ve not seen cognitive disorders in horses before but maybe this is an age-related CD problem? Anyone else gone through this? Contemplating euthanasia before he hurts someone but want to give him every chance to live out his life. Balancing that is hard, hard, hard.
It sounds like maybe he has. 
Pergolide can absolutely make some horses anxious or aggressive.
If you feel he’s otherwise still healthy, I would get some APF and see if that helps him at all.
He has not. I believe I posted “But now is showing aggressiveness toward people - pinning ears, whirling - not biting, not kicking, but threatening.”
Thank you. Great suggestion. APF Pro worked well for a boarder’s horse who went through “pergolide veil.” I will be ordering some today. Appreciate the follow up about anxiousness and aggressiveness.
I meant that at 30, terrified of snow in the beginning of winter, maybe he has lived out his life and is trying to tell you he’s done. 
He has lived a good, long life already and if there is any risk to someone who must handle him, like barn workers, vet , farrier etc ( even you) it sounds like it is time.
I have been looking into alternate treatments on the possibility that the issues may be caused by long-term Prascend use. (And thanks to a suggestion from a thread contributor, he has been started on APF Pro - surprisingly, as he’s an extremely picky eater, he is happily consuming a large scoop of soaked beet pulp pellets as “carrier” for the APF Pro.) As his labs haven’t changed much if at all - that is, if they were showing his PPID was worsening - perhaps an alternative approach would help him. BTW he has known the farrier for over five years and he is pasture trimmed in a quiet place where there is no activity but he can see one of his buddies. My farrier has been aware of the issue and we are both extremely careful and he has not even fidgeted once being trimmed. Hopefully that will continue as I try to give him as much of an opportunity to live out his life as safely as possible.
Possibly, but if you could see him jetting around his turnout flagging his tail and prancing like a two-year old, you might have to rethink that!
FWIW, I have seen full-on terrifying aggression reverse itself with belly meds - the horse in question got started on aloe (60cc GEL 2xday) when he started actually refusing his feed. He’d been getting dealing with DSLD discomfort for many years and had then had an abscess that made him full on lame and needed NSAIDS to help with that.
Boom, years worth of “it’s just who he is” melted away in under a week. I felt dreadful for that horse and grateful he wasn’t mine so I don’t have that guilt hanging over me until the day I die.
I’ve seen similar (if less dramatic because they were less miserable in the first place) reactions to Sucralfate. That’s my personal choice, but it is definitely more expensive than aloe, and hey, the aloe worked for the disaster zone horse, so … maybe worth trying something to see if there is a belly/guts factor at work.
