The reality is that there are too many factors that cause a variance in results.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8717092
I am oh so lucky to have genetic variations in every single P450 enzyme listed in this study on HQC AND in the MDR1 transporter gene. Unclear how many of my variations directly effect the break down of this drug. Unfortunately, it appears the tests to show how your body is breaking down the drug is only available for research. You can only get the total..not the broken down metabolites.
For people like me it would be a total crapshoot. I don’t take Plaquenil for autoimmune issues. Too risky and too much not known. Of course, if my problem skyrockets I may have to change my mind.
Given how hard it was for me to figure out this issue i would say there are likely quite a few people who have the problem and just don’t know it.
for people who have their DNA..here is one study trying to figure out how the variations made a difference on HQC treatment for COVID
https://www.degruyter.com/document/doi/10.1515/dmpt-2020-0164/html?lang=en