I'm going to shed some light into the substance called Ephedrine, its comes from the ephedra plant. Its used in a couple of ways,
1)Inhalers (Ephedrine Sulphate)
2)Slimming product (Ephedrine Hydrochloride)
This chemical affects the CNS (central nervous system), which triggers a metabolising effect and well as a momentary energy surge. If its coupled with caffine (a stimulant) the effects is abt 25% enhanced, vary from ppl to ppl. The drawbacks or side effects are,
1)Incresed blood pressure
2)Increased heart beat
3)Stroke (the worst of the worst case side effect)
The "high" ppl feel from it is from the increased blood pressure, or shall i put it simply its "light headed". There is a limit of Ephedrine that can be taken daily calculated on the concenration of the dosage against the poison threshold of ephedra.
Hope it clears some misconception on it..