The Coca leaf has addictive qualities, that's why the Aztecs would put anyone under 50 who used it to death.It would become a cash crop and pirates would be after coca leafs as much as gold.
There were people messing around with chemistry in Europe,one of them might try to refine it.If there's money to be made somebody will do it.
People in Bolivia, Perú and Northern Argentina and Chile still consume Coca leaves regularly. It is a strong stimulant but not more addictive that coffee, tea or yerba mate and has little to no side effects besides anything associated with caffeine. A cocaine epidemic in the 16th century is ludricous.
I also have not heard of the Aztecs using coca, since it is consumed mostly in the Andes.