Ok..I put my mare on it yesterday because she is lame...We don't have a clue where or how she is lame. There is no heat anywhere apart from a bit on her 'Underarm' area..I don't not think she is pain because she let us stretch the leg etc.
I lunged her today and she was perfect. Was it the bute or the box rest? I had her in for two days now and on bute for a day. Would it work that quick?
I use Bute like I would use ibuprophen for me. If I know why a horse is sore, then I will use some or asprin to help alleviate the pain. If the symptoms don't resolve, or I'm not sure why the horse is acting sore, then I won't use it until I can figure it out, or call the vet.
It does mask the pain. Whether or not it is good depends on your point of view. Pain is nature's way of saying something is wrong. If you mask the pain, the horse has a change to re-injure himself because he doesn't know he's sore/sick.