I am currently on adderall. I read that adderall has 25% Levo-Amphetamine, which has little CNS activity but much peripheral activity, which is associated with side effects and nervousness. So I'm thinking about switching to dexedrine.

I have read that Dexedrine Spansules are a little "weak" or "wavy" in its release. If anyone has experience with the Spansules: how many hours do Dexedrine Spansules effectively work? Does it wear off early?

Thanks.

I believe that the spansules release the dexedrine in two equal "bursts" - the first when you take it and the second around 4 hours later - The beads inside the capsule are coated so that half of them stay around for about 4hrs - but this will depend on your metabolism, so there is going to be some variation. I find that dexedrine is effective for about 5 or 6 hours - at least in my body, so if I took spansules they would last about 12hours (I take the regular release as I like the flexability they offer). Many ADHD extended release medications release in waves - they are more effective in "waves" vs a slow continuous release, I gather.
With regards to the L-amphetamine salt in the adderall - the percentage of this isomer would be 12.5%, since 25% of the composition is "d,l-amphetamine aspartate monohydrate" and in a racemic mix like this, the levo component would be 50%.
I'm not sure how effective the levo isomer is vs the dextro in this salt - for most drugs the levo isomer is less effective, but I think it does depend on the drug in question. Due to it's composition, Adderall is less stong than dexedrine on a mg to mg basis, so you'd take slightly more Adderall than dexedrine for the same effect. Adderall is reported to be "smoother" than dexedrine, but I have no direct experience with Adderall, so I couldn't say, but I do find dexedrine to be much smoother than ritalin - for me anyway.