I don't know how similar/dissimilar Dexadrine and Adderall are, but they have really different effects on me. Adderall made me feel high, and seemed to encourage me to focus like a laser beam on low-level details. Dexadrine, on the other hand, has a very subtle effect on me. I've never felt high when taking it. It's more like a gradual transition into being able to focus at will. When it wears off I can no longer focus easily. On weekends I usually take half the usual dosage, and sometimes I skip taking it all together. When I skip it, aside from difficulty paying attention/focusing, I have mild withdrawal symptoms like feeling tired, headache and an increased appetite.

Having said all this, I want to point out that my doctor told me that different medications work for different people. I may just be lucky enough to have the right body chemistry for a drug like Dexadrine to work well for me.