I recently got Dexedrine 5mg tablets from the pharmacy after almost running out of older tablets. The stamp on the tablet is different. The older tablets are from 2013. When I took the new tablets I felt no change--I was tired and lacked focus as usual. Today I took one of the old tablets and felt a lot different (increased awareness, heart rate, etc.). Has the forumla changed? I don't like taking more than 5mg because I get paranoia.