Last year I took ephedrine(ECA(Ephedrine Caffeine Asparten) for about 4 mouths in a row, and I got addicted to that thing. I had problems keeping my erection while I take it.
I still take it same times when I have to go to the gym and I feel lazy, but when I take it my sex sucks.
I think it act like cocaine. Same of my friends take cacaine, and they told me that sex sucks after sniffing.
However I would sugest ECA for woman, gals never get tired, You can fuck her for 3 hours and she will ask for more. I love when gals get frenetic.