I read this article today that my farrier shared, its an interesting read which raises more questions than it answers but I think worth taking 5 mins out so the you know the questions to ask your vet should the situation arise
http://www.americanfarriers.com/articles/6952-phenylbutazone-my-investigation-and-questions
http://www.americanfarriers.com/articles/6952-phenylbutazone-my-investigation-and-questions