Ephedrine: 

A review panel comprised of Dr. Stephen Kimmel, M.D.; Dr. Grover Hutchins, M.D.; Dr. Theodore Farber, PhD, and four other renowned authorities on ephedra supplementation in Washington D.C., got together in a comprehensive multidisciplinary review of ephedra's safety. The panel met because they felt the US FDA's most recent statements on ephedra caused confusion and generated questions about the supplement. According to the panel, concerns over ephedra's safety were sparked back in 1997, when the FDA proposed a ban on the marketing of ephedra for use in weight management. The ban was based primarily on over 800 reports of alleged "adverse events" the agency had received, but NEVER reviewed, over a four year period. 

Congress and a General Accounting Office report establishing that the FDA's proposal had no valid scientific basis, the most controversial portions of its proposal on April, 3 2000. After reviewing the FDA's reports as well as other published clinical studies investigating the herbs safety, the panel concluded that there is NO link on adverse effects if used in accordance to the American Herbal Products Association (Read the label in other words!)

Now.. to my opinion... I believe the herb is ok to use as long as you first, check with your doc, second, have no heart problems, third, are not taking any medications, prescription or otherwise.

 If you feel the sensations of rapid heart beat, hot, sweaty, over all not feeling well and so on.. this means that the herb has sped up your metabolism. You feel this when you are working out but because you are working out, it doesn't bother you. I would say that you would need to cut back your dose to half and try again. I had to work my way up to taking 3 per day. It is just like any other med... if it makes you feel funny, ease your dose. (of course, that is what your doc would do for you!)