Also Jay...IMO straight eph is far and away better then the extract stuff. You know what quantity you are exactly getting...seem to get less sides, and kicks in quicker...just me though.
Probably just in your head. E. sinica contains almost 80% ephedrine with a little psuedoephedrine. Like a said before, serum concentration times and pharmacological effects are the same between both according to documented research...but either way, I prefer the convenience of the all in one Xenadrine...
White, L. M., Gardner, S. F., Gurley, B. J., Marx, M. A., Wang, P. & Estes, M. (1997). Pharmacokinetics and cardiovascular effects of ma-huang (Ephedra sinica) in normotensive adults. Journal of Clinical Pharmacology 37, 116-122.
Gurley, B. (2000). Extract versus herb: effect of formulation on the absorption rate of botanical ephedrine from dietary supplements containing Ephedra (ma huang). Therapeutic Drug Monitoring 22, 497.
Haller, C. A., Jacob, P. III & Benowitz, N. L. (2002). Pharmacology of ephedra alkaloids and caffeine after single-dose dietary supplement use. Clinical Pharmacology and Therapeutics 71, 421-432.
Those are articles I based all this on if your interested in doing some reading. Also, check in the articles section. Draven posted a paper I wrote that discusses all this in depth.
J