Clinician adoption of genetic testing for drug metabolizing enzymes: is patient safety the low-hanging fruit of personalized medicine?

With the advent of low cost genotyping, personalized medicine (PGx) has entered the clinical realm. PGx assesses inter-individual variability of drug metabolizing enzymes prior to drug therapy. Consequently, toxicity based adverse events stemming from patient metabolism may be avoided. This paper considers two applications: a genetic test of the CYP 2C9 enzyme prior to administration of the anticoagulant warfarin, and a test of the thiopurine methyltransferase gene prior to initiating therapy with mercaptopurine drugs. Clinician experience has been limited and the biomedical literature suggests that is due to barriers to PGx. These include a perceived lack of efficacy from an absence of prospective clinical trials, legacy pharmaceutical industry and physician business models, inadequate regulatory oversight, payer reimbursement practices, and physician habits. Until these are addressed, it is unlikely that PGx will achieve wide usage. Unproven utility and entrenched business models are the most significant impediments to clinician adoption.