^^^Wow 50mg IV seems like a guaranteed panic attack in the absence of benzos or opioids.
The problem with 4f-mph as a recreational drug is likely do its higher potency as a dopamine reuptake inhibitor than a norepinephrine reuptake inhibitor. Methylphenidate is a pretty balanced reuptake inhibitor, being similarly efficacious at the DAT and NET. This gives it far more of a rush and adrenergic push than 4f-mph and isopropylphenidate (which is even adrenergic than 4f-mph). Drugs that are primarily dopaminergic appear to be less reinforcing than drugs that are more balanced.
4f-mph appears more dopaminergic and less adrenergic than methylphenidate which limits its abuse potential. It may be that high doses are disproportionately more rewarding than low doses as the perhaps that when its adrenergic qualities are more perceptible.
I used to abuse hell out of methylphenidate daily for years and would feel the urge to redose after about 1 hour and 10 minutes (i used to time it). The 4f-mph is slower acting and longer lasting, and combined with the fact that it isn't euphoric, means i don't find myself compelled redose. The come down, like methylphenidate, is quite smooth.
Let us know what happens, im always curious about peoples impressions of 4f-mph.