I have read that there may be 10% of the population who do not get pain relief from opioids. There are many reasons. Here are a couple of sites that may be useful.http://sciencenordic.com/genetic-defect-makes-some-nearly-immune-morphinehttps://www.ncbi.nlm.nih.gov/pmc/articles/pmc5447546/
I don't get anything from morphine, nothing but severe nausea from codeine (which is metabolized into morphine), and just figured out that oxycodone is useless for me too. I get some relief from hydrocodone, and great relief from high doses of hydromorphone (Dilaudid), which is what hydrocodone metabolizes to in part. My mother didn't react to morphine either, and my son is the same as me. Some of our ancestors came from Norway.
I would like to find out how and where one goes to get genetic testing.