Substituted amphetamines were already very popular in the 1950s.
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https://www.cbc.ca/news2/background/friendlyfire/gopills.htm...
But I'm not a doctor either so who knows really.
I wouldn't recommend them in general, but mostly because they last too long to really work with a normal 16/8 sleep cycle and the other stimmy effects can detract from things other than focus work.