Also known as Provigil. It has some serious side-effects https://en.wikipedia.org/wiki/Modafinil#Side_effects and requires a prescription in the US (Schedule IV controlled substance). However adrafinil is currently unregulated in the US, and your liver will metabolize it into modafinil with a half-life of about 1 hour.
I know side effects are the exception but they exist, even at normal doses. From the PDF linked from wikipedia: "Common side effects that can happen in anyone who takes modafinil tablets include: •back pain •headache •nausea •feeling nervous •stuffy nose •diarrhea •feeling anxious •dizziness •upset stomach •trouble sleeping"
