I am not putting anything into my body unless I know exactly how it works. Most of us have what we need to succeed in life and love and drugs that have unknown consequences can damage us in horrible ways.
Anyway, that's my take on the subject; you may not agree; it's your body, your mind and your life.
Just thinking...
Watch out for that Modafinil and Ritalin (methylphenidate).
FIDE's Anti-Doping Rules already account for these drugs, I believe.
Caffeine was also tested, but its effects weren't deemed statistically significant.
Article
Slower play, though. So forget about using these drugs for short time controls in online chess servers.