Dexedrine .... side effects | ADHD Information

I have 7 yr. old twins that are ADHD, my son is hyper and has been on Dex. for the past year, it works great, and hes a joy (most of the time) to have around, aside from his neverending babble.   His sister is ADD, in the daydreamer way, I put her on Dex. a couple of months ago, starting with 10 mg. (slow release) and it was working great, the ped. put it up to 15,( the same amount as my son's) and in the past month she has become very slow, not daydreamy, just incredibly slow, shes also become defiant with her teachers ( always has with me) and tends to draw nice pictures then scribble all over them and ruin them.  I have taken her off the pills for this weekend to flush her system, getting a ped. appt. will take about 2 months, should I put her back to 10 mg. or wait till I see the ped.  this is getting so frustrating for everyone, including her.  Anyone else ever see their child go into slow motion after being on dex.??My son could not take Dexedrine. He was on 10mg of SR at the age of 7. He wouldn't eat a thing and he lost 4 pounds in a month. He just lay on the couch holding his stomach and saying it was sore.My son did the same thing for the first month, he also lost 20 lbs in 3 months, but for the past 7 he has stayed the same weight (underweight), but has been increasing his appitite, and starting to fill out again.   And as I said before, he may have his moments, (like any child) but otherwise hes a dream.  Its my daughter that I am so worried about, shes only lost 5 lbs (good) and only complained about a tummyache twice, but she has slowed down physically and mentally.  I even have to encourage her to walk! or otherwise she just stands there, she says shes not foggy, just slow.   It's like watching"The 7 Million- Dollar Man" all over again.