Ibuprofen is not a good drug for endurance athletes, at least thats what a lot research claims.
If youre contemplating taking drugs to get yourself through first ask yourself if you really need them, secondly go and see a doctor/pharmacist. Im sure the forum is a wealth of knowledge on many subjects but if there is one thing you should see a professional about its taking drugs.
and many professionals have no effing clue about using meds in endurance events
the evidence on using ibuprofen in endurance events is sketchy to say the least. one study was done on it's use by ultrarunners and the general conclusion was that it's not suitable to use regulalry to prevent ultra pain. well - duh - tell me something that isn't from the Uni of Stating the Bleeding Obvious.
but that's the key with strong painkillers - only take them if you NEED them, not if you THINK you need them. don't train using painkillers as they can mask underlying serious issues, but for one off use in a race, then they are fine if taken ar recomended levels. they are meant to get you to the finish, not to solve any major issues.
and frankly if you's starting the race knowing that you need painkillers to see you through then you are your own worst enemy. you know you shouldn't be racing so don't.