is the primary ingredient in the synthesis
of crystal meth
(speed, crank, etc.). 1000 Ephedrine pills typically yields 1 lb. of meth.
Ephedrine is also a common adulterant or substitute in Ecstacy pills. Dealers hard-up for cash and not afraid to beat-out a few dumb kids will often sell Ephedrine as E (at a huge profit). Not only is Ephedrine relatively inexpensive, it also causes a couple of sensory effects (like tingly scalp, increased energy, etc.) that, when combined with the placebo effect, make it easier to get away with the rip-off.
One way to prevent being ripped off in the fashion is learning how methamphetamines taste, and how Ephedrine tastes differently. It takes some practice and experience, but this is a good way to field-test pills.
The best way to field-test your pills is with the Marquis reagent, which is useful for determining presence of MDMA, 2CB, Speed, and DXM in a pill. Organizations such as Dancesafe, Erowid, and Lycaeum can show you where to buy a bottle of the Marquis reagent. Note that the Marquis reagent is only useful for qualitative analysis, NOT quantitative.