I was an avid Ephedra (ma huang) user in the past for many years and I remember sometime in 2008/9 it just stopped working for me... I never abused it, only used on work out days and used only just before a workout (never took through out the day)... What I loved about Ma huang was the focus, the euphoria motivation to workout and the love the inherent side effect of maintaining disciplined eating (almost too disciplined). For years I have never had that awesome push for workouts/motivation with any kind of supplement.. A few months ago (beginning of 2018) I discovered Modafinil.... It worked great and I had some awesome workouts and motivation but it quickly stopped working after about 30 days... and now back in the same unmotivated rut.... for years since I started TRT I thought maybe I had a thyroid issue (hypo or pooling, RT3, etc...) but now I am thinking I may have a neurotransmitter problem(ie... dopamine, serontontin, etc....) Im thinking I should concentrate on increasing my dopamine production through tyrosine supplementation and phenylthylamine... anybody have any thoughts and/or experience with this stuff... anybody familiar with injectable tyrosine????