Pharmacogenomics in practice


Inside the USF Health community pharmacy. (Photo courtesy of USF Health)

As an undergraduate student in my genetics class, I pondered if the subject would actually have applications in pharmacy school. Between memorizing the stop codons and making sure not to confuse meiosis with mitosis, genetics was a challenging class. While I enjoyed it, I never made the connection to how it applied to pharmacy practice because it largely focused on inherit genetic conditions. 

Fast forward to my third year of pharmacy school, sitting in the Translational Pharmacogenomics course. All of a sudden, the connection between genetics and pharmacy came together through pharmacogenomics. Pharmacogenomics looks at how genes influence an individual’s response to medications. During the semester, we learned about the basics of pharmacogenomics and how it affected drug metabolizing enzymes, transporters, and targets. The course then transitioned into the clinical applications for different drug classes using the Clinical Pharmacogenetics Implementation Consortium guidelines. We then focused on patient counseling skills, real-world implementation, and understanding ethical, legal, and social issues.

The implementation of personalized medicine in health care is making waves in the curriculum of health care students. Pharmacogenomics is 
another component of personalized medicine that is still new enough to where not all health providers are aware of its roles. When I learned there was an option for an elective rotation in 
pharmacogenomics, I had to enroll.

Immersed in the process

My pharmacogenomics rotation took place this past fall at two different sites at USF Health: a community pharmacy, and a clinic with genetic counselors and medical geneticists. 

At the pharmacy, there is a designated consultation room for patients referred for pharmacogenomics testing. I put my pharmacogenomics knowledge to practice through the process of reviewing pharmacogenetics results, counseling patients on their results, and creating consultation notes to be placed in the patients’ health records. 

Drug information and literature evaluation skills are crucial for potential links between a medication and the gene of interest. I also had the opportunity to sit in on the discussions of the Personalized Cancer Medicine Service at Moffitt Cancer Center. The 
discussions center around finding molecularly targeted therapies for somatic mutations identified from a tumor 

Every patient I encountered has been more than intrigued learning that their genetic results are influencing the way their medications work. Many factors contribute to how a patient responds to medications, whether it be an adverse drug reaction or ineffective therapy, and these tests oftentimes help explain a piece of the puzzle. Many times these are patients who have become very frustrated with their therapy and are happy to find out that their genes are part of the reason their therapy is not working. 

Case study

One patient I encountered during the rotation was experiencing adverse effects from her antidepressant therapy. She was on escitalopram (Lexapro) and was referred to us by her primary care physician to evaluate if there were any drug–gene interactions. When the patients genetic results came back, it was determined that they were a poor metabolizer of CYP2C19. Escitalopram is metabolized by CYP2C19 to an inactive metabolite. Additionally, I identified a drug–drug interaction with escitalopram and omeprazole. The combination of the patient being a CYP2C19 poor metabolizer and on omeprazole, a CYP2C19 enzyme inhibitor may have contributed to the adverse effects reported by the patient. We recommended to the patient’s provider to consider a 50% dose reduction, 
consistent with the CPIC guidelines.

The possibilities

Like any emerging field, pharmacogenomics information is constantly being updated and released, keeping health providers on their toes. Many people I speak to, including health providers, are still not familiar about the clinical applications of pharmacogenomics, but find it very interesting when I explain the concepts to them. With the way this field is progressing, the idea of it will not be too far out of reach. Instead, pharmacogenomics will be part of standard care where patients will have pharmacogenomic results that are taken into consideration before a medication is prescribed. I cannot wait to see how this field will change patient care.

18B_Amanda-Elchynski---On-Rotation.pngAmanda Elchynski is a final-year PharmD candidate at the University of South Florida College of Pharmacy.