A Pharmacist's Thoughts On Pharmacogenomics Testing
In our latest question and answer, the pharmacist discusses pharmacogenomics testing (i.e. genetic testing for optimal drug therapy).
I'm so happy to have found your site. What is the Professional Pharmacists perspective regarding PGx screening? I look forward to hearing your views.
Pharmacogenomics, or the study of the genetic variation in drug response, has recently shown mixed results in terms of clinical and economical value. More evidence is needed to better understand the best way to utilize pharmacogenomics, however, there are many applications that are clinically relevant today.
Personalized medicine and the field of specialty drugs in general continues to show promise in providing therapies for cancer, autoimmune disorders, and many more. Below, we will discuss examples of evidence supporting pharmacogenomics.
Coumadin (warfarin) is one of the oldest and most widely used anticoagulants in the country. Because of its narrow therapeutic index, where prescribers must balance the chance of clotting versus the risk of bleeding, warfarin dosing is critical to get right for each patient. Testing patients for CYP2C9 and VKORC1 variants can help make more informed dosing decisions during patient therapy, although guidelines do not currently support routine testing of patients.
Plavix (clopidogrel) is another critical cardiovascular medication that is important in preventing heart attacks and strokes. Patients that are poor metabolizers of CYP2C19 may not respond well to clopidogrel, leading to worsened clinical outcomes.
Infectious Disease Drugs
One commonly tested genetic variant for HIV medications is abacavir. HLA-B*5701 is strongly recommended to be tested prior to beginning abacavir regimens. HLA-B*5701 positive patients should not be prescribed abacavir due to a significantly higher risk of side effects including fever, rash, and other hypersensitivity reactions.
Several oncology regimens are dependent on pharmacogenomic testing to guide therapy. Both the tumor and the patient’s genetics must be taken into consideration for optimal care. Regimens that are especially impacted by pharmacogenomics include irinotecan, erlotinib, and trastuzumab.
To summarize, several advances have been made in pharmacogenomics over the last couple of decades, however, much more work is needed to understand the true value of pharmacogenomics for optimal clinical and economical outcomes. As medical care becomes more advanced, specialized, and complex, pharmacogenomics will be increasingly relied upon. As a pharmacist, pharmacogenomics is an exciting field that I look forward to being actively engaged with in the future.
Source: Genomics and Drug Response, NEJM