Genetic Testing Makes Medication Therapy Selection Personal

An Expert Interview With Mary Roederer, PharmD, BCPS

Troy Brown

March 30, 2012

March 30, 2012 (New Orleans, Louisiana) — Pharmacogenomics, the identification of genetic factors that affect the efficacy or toxicity of medications, is a field that is growing rapidly. Research is improving medication therapy management of patients by helping pharmacists and physicians predict how a patient is likely to respond to a given medication.

In addition, pharmacogenomic research is contributing to the development of evidence-based guidelines on the interpretation and clinical application of pharmacogenomic test results. Pharmacogenomic evidence is also assisting health officials with selecting medications for use in large populations of patients with a given disease.

Pharmacogenomics: Getting Personal in Medication Therapy Management and Beyond was presented here at APhA 2012: American Pharmacists Association Annual Meeting and Exposition.

Co-presenter Mary Roederer, PharmD, BCPS, from the University of North Carolina at Chapel Hill, spoke with Medscape Medical News about recent pharmacogenomics research and how pharmacists can use it clinically. She also discussed how pharmacists are working together in the United States and internationally so that people in developed and developing countries alike can benefit from the latest research.

Medscape: Why is pharmacogenomics becoming so important?

Dr. Roederer: Pharmacogenomics in general is very relevant to pharmacists in primary care. Several studies have shown that as many as 1 in 4 prescriptions have some sort of pharmacogenetic variant that's relevant. This information helps pharmacists and primary care physicians make decisions about medication therapy.

Medscape: The American Pharmacists Association recently added a pharmacogenomics section to its DrugInfoline newsletter. Why was it important to include this section in the newsletter?

Dr. Roederer: The editor decided it was important because there is a lot of literature amassing about pharmacogenomics and how that relates to drug therapy.

Also, the American Pharmacists Association (APhA) decided to add pharmacogenomics as one important factor to consider in medication therapy management, and they released a white paper about that in the November/December (2011) issue of the Journal of the American Pharmacists Association.

A perfect storm of activities going on in the research arena, the practical nature of the APhA looking at medication therapy management, and the need for pharmacists to know more about the area…culminated in them identifying that as an area for the newsletter.

Medscape: What's happening in research right now, and how is this research affecting the practice of pharmacists?

Dr. Roederer: More of the bench-type research is being translated into outcomes that patients care about, and it's even gone so far as the development of several evidence-based guidelines on the interpretation of pharmacogenomic test results, and how that should affect drug therapy. A couple of organizations have spearheaded this. One is the Clinical Pharmacogenetics Implementation Consortium (CPIC). The Dutch Pharmacogenetics Working Group has released similar guidelines that are more comprehensive, whereas the CPIC looked at specific tests for specific drugs.

Pharmacists like evidence-based guidelines, where people have thoroughly reviewed the literature. I think that's going to make it more practical at the point of care.

Medscape: What are some medications whose effects are influenced by genetic variations?

Dr. Roederer: There are certainly a lot of oncologic drugs that are affected and involve tumor genetics. Warfarin is an anticoagulant, and the genetic tests that are important to evaluating its efficacy are the CYP2C9 test and the VKORC1 test. The genetic test that's important with clopidogrel [Plavix, sanofi aventis] is the CYP2C19 test.

Medscape: What are some criteria for determining if a genetic test is appropriate for clinical use?

Dr. Roederer: I like to think of it in the context of how pharmacists would consider any change in therapy for a patient. I ask myself:

  • Is the drug necessary?

  • Are there alternatives?

  • Are there alternatives that might not necessitate the use of a genetic test?

  • Is there a valid test? (It may not be worth getting a test if you're not sure of its validity.)

  • Are these recommendations that are going to be accepted by the medical community, other pharmacists, patients, physicians?

Medscape: How can pharmacists interpret and apply this information during medication therapy management right now?

Dr. Roederer: Probably the best way is just to integrate it with medication therapy management, the way that pharmacists typically do anyway, while they're considering the patient's medication therapy management in general.

Is there appropriate turn-around time for the test? If it takes 2 weeks to get the test result, and they need it within 2 days to make a change in therapy, then that's not very good.

Also, is there good evidence [for giving the drug]? For example, if you're dealing with one of these things that has evidence-based guidelines, that would be an area where you'd feel very confident using that information.

Is there acceptance by the prescriber, by the patient? Is there insurance reimbursement?

How do you evaluate the results and document in the medical record? I think that's unfortunately one of the areas that needs to grow the most — where can we document this information in the medical record so it can be used in real time, in clinical decision support?

Medscape: What is the Pharmacogenetics for Every Nation Initiative (PGENI)?

Dr. Roederer: The Pharmacogenetics for Every Nation Initiative is a very, very interesting project, where what we're trying to do is collect data and glean genetic data from subjects in 104 developing countries. These are countries that have enough infrastructure to implement something from the Ministry of Health level, but not so much money that they could do genetic testing at the individual patient level.

When we get this information from the different ethnic groups that comprise a certain percentage of the population in these countries, we can start to fill in the map of how their genetic code for something specific that affects drug therapy differs from, for example, US Caucasians. A lot of the drugs historically have been developed and tested primarily in Caucasian populations, and primarily in men between the ages of 18 and 35.

We see that we can use that information about how the drug is metabolized and transported, and what the drug target is, to see how drug #1 used for treatment of disease "A" could be better than drug #2 for treatment of disease "A", based on how these genetic factors come into play.

For example, there are 4 different World Health Organization–approved treatments for malaria…2 of them are not utilized in much of Africa because of resistance. That leaves 2 alternative treatments; 1 of them is affected by CYP2C8, so it is metabolized by CYP2C8, and some of the sub-Saharan African population that is plagued with malaria may have something like 1 and a half to 3% of the population that has a variation of CYP2C8.

That doesn't sound like a lot, but when you multiply that by the million cases of malaria that are treated per year, it starts to affect a large percentage: 15,000 patients. So 15,000 patients are at risk of having a toxic effect because they have decreased metabolism of CYP2C8. So perhaps that fourth regimen for treatment of malaria would be the best choice for that patient population. We're trying to attack things at the drug policy level within the countries, at the Ministry of Health or the National Medication Review Authority level, so we're going after drug formularies or central medicines lists in these countries.

Medscape: What do you see in the future for pharmacogenomics?

Dr. Roederer: In the genomics arena in general, which is bigger than pharmacogenomics, people are meeting and deciding how information technology should utilize this information, where it could go. The information is only going to get bigger and bigger, as whole genome sequencing becomes more of an inexpensive reality.

Medscape: Is there anything else you'd like to add?

Dr. Roederer: We know that there needs to be a lot more education about this issue because a lot of schools of medicine and pharmacy still don't include even genetics as a large part of the curriculum, and pharmacogenomics has even a smaller proportion of the curriculum in their clinical degree programs. We know that, not just for people who are currently training, but for people who are currently practicing, we need to find ways to help them understand the issue more so they apply it to patients.

Dr. Roederer is a Board Member/Advisory Panel with the American Pharmacists Association.

APhA 2012: American Pharmacists Association Annual Meeting and Exposition. Presented March 9, 2012. Abstract

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