As a child I was put on methylphenidate and it severely screwed me up. It can cause mania and auditory hallucinations. For me I experienced this:

Methylphenidate was really bad mentally. I was on that drug for a while. That was when my symptoms of "ADHD" got the worst. You see everything methylphenidate is supposed to prevent is caused by, well methylphenidate. It made my brain unfunctionabally foggy, and a bit reckless. My feelings scared me and didn't feel like my own, and I didn't like what I thought. They were things about defiance to my grandma, and violence, which I tried not to follow. I didn't want to do some things, but with the the drug affecting me it was hard, and confusing. It was hard to convince my psychiatrist to get me off of them because of that, but I got off. Now I'm doing fine. I am in good health and have all A's and proud teachers. My behavior problems were caused by dealing with domestic violence, being parented by a father with Narcissistic Personality Disorder, stress, and being gifted.

You might not want to know what's going on in your son's mind, and he might not understand it himself, but you might not want to use Methylphenidate, I also find the company to be very dishonest, and I don't trust it. Welcome to ADHD, the disease that was bought into, created simply by environment, underconfidence, and simply believing in yourself that you have it (ADHD). I know a boy who has suffered from ADHD by believing he was incompetent because he had it, and that it was an excuse. So he's lazy, doesn't try, and doesn't apply himself. He believes it's because he has ADHD. But it's not. It's his belief in it. It's amazing what you can achieve if you believe in yourself. Maybe someday he will recognize this, and say this was me. I hope he does. He's very, very, nice, and this level is preventing him from his potential, one absence of a label away.