I doubt most of these stories, especially where the horse is 'crazy' when the drug wears off. I've had my horse given reserpine (so it could calm down and heal while on stall rest for a bad leg injury). There was absolutely NO 'crazy' when the reserpine wore off. She just went back to standing on her hind legs and doing Lipizzaner leaps while I was hand walking her. A lot depends on dose. My friend's off the track Thb got resperpine after he broke his hip, and he spent the next six weeks sleeping away most of each day. Snoring like a lumberjack. My mare, on the other hand, spent about FOUR days not leaping and rearing and tap dancing on my head. She was bright eyed and very alert during that time. And it wore off quick. When it 'wore off' she just gradually went back to her old pattern of behavior. In my experience, there is a very different deal behind the story of this happening. It's about getting a horse sold that's a tough ride, but not talented enough to attract the riders who could handle him. Dealers have many ways of doing that, medication is just one. The LEGITIMATE use of medications like reserpine is to prevent injury to horse or rider, to calm a horse while it's recuperating from an injury and there is a danger of him reinjuring himself, or get a horse through a behavioral crisis (again, here, the priority is preventing injury to rider and horse).