Opiods and other pain drugs are odd. Doctors are finally starting to admit that people complaining of pain aren't faking. Actually, whites have a surprising percentage of opioid resistance and Asians has a huge amount, if you look at the studies/genetics.

Unfortunately, this means they need bigger dosages and is correlated with increased susceptibility to addiction. They chose the right drugs for the opium war and the current fentynal type drugs. Luckily for the Asians, they now have a culture very much against those type of drugs so are less affected by the fentynal/morphine drugs coming in.