The idea of genetically testing people for drug suitability is causing them [Drug Companies] a bit of a headache at the moment, as they’re desperately trying to think of ways to make money out of it.
Pharmacogenomics has to be one of the most misunderstood areas of drug development today. We’re used to the idea by now that our genes do not determine who we are. Genetic inheritance puts us at risk for some diseases more than others, makes us more or less likely to excel at certain mental or physical tasks, influences our adult height or weight. But strong effects of single genes are rare. Instead there’s a complex interacting system of multiple genes and environmental effects that, based on what we now know about complex systems, will not act deterministically, but rather affect the probability of future events.
It seems clear that, unless there is a strong single gene effect on something like proteins involved in drug metabolism and clearance, genes will have an uncertain influence on response to drug.
In the end, knowing some one’s genetic background, like knowing their particular symptom complex, will inform the physician about where to start therapy and the chances of success. But there will never be a way of “knowing” if that means a high degree of confidence in knowing the outcome of therapy.