Thank you for your question and welcome to ADHDCentral.com   Since people react differently to medications, there is no way to say which medication would be best for you. Sometimes it is a matter of trial and error to find the right medication and the right dosage for you. If you are feeling sick, you should certainly contact your doctor. Although most side effects disappear after a few weeks, if your side effects are interfering with your ability to function (and yours sound as if they are), your doctor needs to be made aware so he or she can determine if you should discontinue or adjust the dosage.   As far as the difference in dosage, this is a difference based on the type of medication. Each medication is dosed differently and one cannot be compared to another.   Eileen