Can we use therapeutic drug monitoring (TDM) to assess PGx?

TDM of the drug in question can also tell us a good deal about a drug's metabolism and will also take into account all the other variables at play (co-medications, diet, impaired organ function, etc.) However, unlike genotyping and probe-drug testing, therapeutic drug monitoring must be performed during therapy, not before. So, in fact, TDM is not really used to predict therapy in PGx but serves as a confirmation of PGx findings.

TDM and genotyping should be considered complementary and can be used in tandem to, first, predict and then verify appropriate serum drug levels.