Therapeutic drug monitoring (TDM) can 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, TDM must be performed during therapy, not before. So, TDM is not used to predict therapy in PGx but serves as a confirmation of dosing. TDM can support PGx findings, but it does not replace them.
TDM and genotyping should be considered complementary and used in tandem to predict and verify appropriate serum drug levels.
