Provigil (Modafinil) is one of the most popular preparations made for treatment of various sleep disorders, narcolepsy, excessive sleepiness and other. Its effectiveness has been proved numerous times and there are not much doubts about that. However the balance is always kept and it is not an exception. Just like any other drug it has particular side effects that those who are going to take it should know in order to be able to identify symptoms and be able to take necessary action in order to avoid possible complications.