There's a good bit of individual variation in reactions to morphine, and I seem to remember reading somewhere that Asians, on the whole, tend to react differently to Caucasians. (Don't remember what the actual difference was.) I found out my personal reaction to morphine when I had a violently painful eye inflammation. The morphine did nothing for the actual pain. It put me to sleep, so it helped, but the pain itself was actually unchanged. It was a bizarre effect.