I've been taking adderall for some time now. My dosage was 30mg xr in am and 20mg xr at 3pm. For me, the XR's only last about 8 hrs. I am now switching back to Dexedrine because I feel it worked better for me. Does anyone know an accurate comparable dosage for the two meds. My doc prescribed me 15mg Dexedrine capsules, he says they last all day, but they are not XR and 5mg Dexedrine Short acting. Am I going to be in for a surprise here? Thanks for the help...

Dexedrine spansules are time release of a type very similar to Adderall XR. I would expect that the dexedrine spansules would last about the same amount of time as Adderall XR. Dexedrine is a little stronger than Adderall on a mg for mg basis, as dextroamphetamine is more potent than amphetamine. I would GUESS that 15mg dexedrine is roughly equivalent to 20 or 25 mg of Adderall.
15mg spansules release 1/2 - or 7.5mg - of medication initially, and then the other 7.5 mg about 4 hour later.

I have no idea what a comparable dose would be, but I can tell you from my experience I did SO much better on Dexidrine than I did taking Adderall. I took 10mg xr Dexidrine (after trying Ritalin with no results) for about 8 years before "trying a medication vacation" for 3 years. When I went back on meds. I took 5mg Adderall xr for about 3 months and it was very different than dex.! For me I felt too roller-coastery like it would come and go, it really frustrated me. I am now back on 10mg xr Dexidrine and feel much better and level. Do what works best for you, sometimes it is the certian drug not just how strong it is/how long it lasts. Good luck!

I do not know whether the extended release would alter the dosage conversion, but with instant release Adderall, a 10m dose contains 7.5mg dextroamphetamine and 2.5mg levoamphetamine. While levoamphetamine does have a stimulant effect, it's CNS effects are negligeble, meaning that it doesn't play a very large role in the focusing effects of Adderall.

However, Adderall involves several different salts of amphetamine, which absorb at different rates. This is a separate issue from the XR mechanisms. This makes it a bit difficult to simply say that 10mg Adderall=7.5mg Dexedrine. While the absorbtion issue is probably moot if you're taking the XR version, since the XR mechanism is a 1200 pound Gorilla compared to the absorbtion rate differences in Adderall, the different salts do make a difference. The reason is because different salts have slightly different weights.

10mg of Adderall would contain 4.7mg of freebase dextroamphetamine if one removed the salts. I cannot find a definitive answer for how much freebase dextroamphetamine would be in 10mg of dextroamphetamine sulfate, or Dexedrine.

The difference is likely very little, and so the 10mg Adderall-7.5mg Dexedrine is probably correct.