My stepmother was just diagnosed with ADD (at the age of 58) and I think I liked her better before she went on meds for it.
Now she just seems high all the time. It's very hard work being around her. She talks a mile a minute.
But she's happier, so I bite my tongue.
My guess is she's on the wrong dose.
One of my kids went on medication at around 8. The doctor never increased the dose and he was eventually weaned off the meds. He is very bright and still has more trouble concentrating than most people at times, but the meds really helped him. He never seemed high or acted differently. I asked him how the meds felt and he said the only way he could tell he was on them was that he could keep his mind on a task better.
ADD has been described as trying to take the SAT test in the middle of a cocktail party.
Cocaine would have the same effect.