I'm sorry your only getting diagnosed now, at 40. I was diagnosed as a child but only started taking medication when I was in my early/mid 20's. Life became a lot better for me after I started taking medication. I hope this puts your life on a new course to a brighter future.
Newer drugs don't equal better drugs. Both Dexedrine and Adderall work great for me.
Thats a good sign! It is also possible that ritalin will work just as well for you. The Dexi has been around longer and is probably cheaper which is why your insurance company went that route.
He originally was gonna put me on adderall but my insurance prefers dexedrine. I cannot believe how focused I am already!
Basically, its stronger then ritalin and not as strong as adderall. Your doc is starting you off low and slow and thats a good thing. It does take some trial and error to find out what works best. Keep in touch with the doc. Take notes as to when you find it wearing off - duration is important.
Here is a link to most of the adhd meds on the market.
http://www.leeheymd.com/charts/adhd_1.html