I don't ride 100 milers, and for that matter, at the moment I'm not riding *any* rides. Still -- If my horse had a case of colic the day / night before a ride - I would scratch him from any competition. Depending on the vet's advice, I would either hang out at camp, or head home. Adding the stress of a ride on top of a colic episode is just dumb.
Something like a stone bruise is more of a grey area. I doubt that attempting a ride with a stone bruise is going to endanger the life or future health of the horse. I'm going to assume that pads were already put on the horse, and he is still not sound. If putting pads on fixes the problem, then no bute is needed. If putting pads on does *not* fix the problem, the the question in my mind is - are we really dealing with just a stone bruise? Me - personally - I would go home and soak his foot, watching out for tendon / ligament strains in the meantime.
So, bottom line - I think riding with bute is asking for trouble. That is for *any* ride, any distance.
Wonder how they will be able to tell what "small amounts of Bute" are?? Did I read it correctly that one of the FEI vets from South America who is an advocate of allowing bute said something like "it should be alright for a horse who has had a slight case of colic the night before the event or presentswith a stone bruise to be administered a small amount of bute so that they can compete, after all, they travel so far. (?) I tried to find the quote again but lost it. PHEW....I keep thinking I am missing something here...please set me straight and explain how it could be that a vet would say that. Another survey: If your horse slightly coliced the day/night before the ride.....enough to be given bute...would you still ride him on 100 mile ride (or any ride)? If your horse presented to the vet the night before the ride and was off and the vet found a stone buise...would you give him bute the next day and ride 100 miles??