How much clorazepate and alcohol would it take to be fatal?

Why take the risk? To the best of my knowledge, there isn't any accurate info on how much of each is needed when mixing the 2 to be fatal, because it will be different depending on the individual. For example, a long-time alcoholic can down couple pints of vodka w/o trouble, but for a nondrinker that would be bad, especially if a tranquilizer is involved. So, don't try it. Don't drink/drive. Be good. Good luck.