I have already mentioned in this review, and it is also mentioned in other reviews, that it is a potent supplement, and it should always be taken in moderation. Since it is metabolized in the body, it can add some strain in the liver during the process and can increase liver enzymes.
There is a reason why there is a recommended dosage, and 400 mg should only be the maximum dosage that can be taken. If taken in large doses, side effects can be quite serious and damaging especially to the liver.
On the other hand, it is also noteworthy that some reviews of online especially its side effects are blown out of proportion. Do not readily believe this as well. If you just take adrafinil responsibly, then you should be able to enjoy its maximum effects without damaging side effects.