neurologists have a variety of noxious stimulants available to them to determine level of consciousness, or depth of coma, or coma vs faking a coma: nipple twisting, pubic hair pulling, thumb pressure on eyeballs , knuckle rubbing on chest, rectal exam...and ammonia capsules. The physician's choice of stim probably tells you more about the physician than it does about the patient. Anyway, if the patient is goofing on the doctor by pretending to be comatose, or is in a relatively light coma, or is just asleep, these stims are annoying enough to cause a reaction; if the level of consciousness is lower (or the patient a really good actor), there is no reaction to the stimulus.
Provigil is indeed a controlled substance, I guess because of its abuse potential, rather than because of side or toxic effects. Its side effect/toxic profile seems pretty benign, certainly better than amfetamine and arguably better than caffeine or nicotine, both of which are legal by heritage rather than by rational evaluation.
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Dance like you have never been hurt, work like no one is watching,love like you don't need the money.