My oldest son is 15 and tried meds last year. He was first given an EKG to make sure that he didn't have any heart issues that would make stimulant medication dangerous. To my surprise, his EKG was abnormal so we had to have a cardiologist review it and he was then cleared to start.
He tried Concerta first and said that he could understand school much better, but that everything interesting and colorful was now gone from his day. He said something like "if real life is this boring to normal people I'd rather not be normal." He ended up having chronic headaches from it so we stopped it after about 6 weeks.
His second medication was Adderall. I saw what seemed to me to be positive changes in his attentiveness to school work, but he was also ridiculously talkative on it. I couldn't tell if it was the medication making him a motormouth or coming off of it at the end of the day that was triggering it, but it was something that quite a few people commented on. It was like a combination of truth serum (he had no filter so everything was suddenly on the table for discussion) and speed, because his speech was so, so fast. But it was usually at the end of day or into the evening, when the meds should have been out of his system. Anyway...he took it regularly for a few weeks and then started "forgetting" and once school was out, refused to take it at all. At one point - and I don't know if he was on it or off it at this point - he was incredibly irritable, to a degree that other people noticed as well. After maybe a week of that, he was back to his normal self.
He was working as a field assistant to a land surveyor this summer so I had him take his medication the first few days because I really wanted him to be able to focus and learn how to use the equipment. One day he refused to take it and his boss remarked at the end of that day "I don't know what's different about him today but he was in a really great mood and was really on and focused the whole day and did really great work today." That was off the meds, so he stayed off of them and hasn't gone back yet.
So that's where we are. He was diagnosed when he was 7 and we tried "everything but" until he was 14. Trying meds wasn't the end of the world but I'm disappointed that we didn't find one that was a good fit for him and now he's unwilling to try anything else, which is fine for now. He's old enough to have a say in his own healthcare and I'm not going to force meds down his throat. He's the one who has to live in his body and brain and deal with the consequences of his impulsiveness and inability to focus. We are going to try more of the "everything but" route...we're looking at a new line of supplements, hypnosis, and testing for celiac or gluten sensitivity.
Good luck with your son - I hope that you find something that works well for him.