I've had some done but not for medication related reasons. Genetic testing like 23andMe is all the rage, but the smart people are saying let's not get carried away. These tests show interesting info about predispositions, but they have to be used in conjunction with functional testing (not psychological testing, whole body testing) and other measures to have real value. Cant just look at genes.

As for drugs pooping out, based on my reading this is due to alterations in brain function caused by the drugs, e.g. in the case of SSRIs the body's own serotonin mechanisms become impaired by the presence of the drug, and thus over time there is a net decrease, and then you need more of the drug, or a new one, etc. In other words, the drugs are potentially exacerbating the problem by depleting the very substance that their whole model says is the cause of the problem in the first place (which has never been validated).