It's estimated that more people today use amphetamines than people used cocaine in 1910

Is that including legal prescriptions or just recreational use?

Because taking a once daily extended release 25mg Adderall is very different from taking recreational amphetamines or cocaine.

Just taking America as example, 1910 has 92 million people Vs 345 million or so today. Also with modern means of transportation + spread/speed of manufacturing of illegal drugs + capture of the political class by corporations including pharmaceuticals are sufficient reasons for that statistic to be not surprising at all.