Comment by LoganDark

d-meth being the desirable one (leaving l-meth undesirable) matches up with my anecdotal experience with adderall, which is approximately equal parts d-amphetamine and l-amphetamine -- it's not quite methamphetamine, but it's closely related.

I was given some by prescription for ADHD, and when I first tried it, it completely destroyed me for some reason -- I could not seem to get myself out of bed to eat (or do much of anything), even when I was very hungry. I ended up having to sleep it off, because being awake for that was very distressing -- not only did it not help me, but it seemed it had caused me even greater executive dysfunction.

When I brought this up at my next appointment, I was prescribed pure d-amph to try next. This actually helped me a lot, and continues to help me to this day.

I can only guess that the l-amph was the problem with the adderall that day. While my body seems to also have issues with different brands of d-amph, they're more like heart issues rather than executive function issues.