Pharmacogenomics currently plays a very limited role in optimizing medication therapy, but the FDA and industry experts are confident that advances in genetic testing will uncover new linkages between drugs and genes that will dramatically improve medication outcomes.
The most common use of pharmacogenetic (PGX) testing is to identify patients who will not respond to a medication — for example, identifying variations in the CYP2C19 gene that is responsible for metabolizing many drugs. Another example is the FDA’s requirement for genetic testing prior to prescribing oncologics that target very specific cancer-causing mutations.
Health plans commonly limit coverage of pharmacogenetic tests to those required by the FDA plus a few others that have proven their clinical utility.
There are more than 150 FDA-approved drugs with pharmacogenomic information on their drug labels, but the FDA concedes that only a few have information on the specific action to be taken based on the results.
The FDA and industry experts predict that the quality of pharmacogenomic information will improve and that the role of PGX testing will expand as the cost of genetic testing plummets and as evidence mounts for relationships between drugs and specific genetic variants.
PGX testing will become increasingly refined to more precisely identify genetic variations that alter the ability of the body to absorb, transport, metabolize, or excrete drugs or their metabolites. That will lead to more accurate dosing, which is important for high-cost drugs.
One of the most promising areas for expanded PGX testing is identifying genetic variants that cause adverse drug reactions. The payoff for expanded PGX testing for health plans will be reduced costs for drugs wasted on nonresponders plus the savings from fewer adverse drug responses.
While pharmacogenomics will improve medication safety and outcomes, it will also place a greater burden on prescribers who increasingly will be obligated to obtain and interpret genetic test results when they are starting medication therapy. But health reforms such as patient-centered medical homes (PCMHs) and accountable care organizations (ACOs) already place increased responsibility on physicians and nurses for other activities, such as preventing hospital admissions and managing downstream health care costs.
That leaves open the question of who has the time to keep up with pharmacogenomic developments and their effect on medication therapy. This has significant implications for health plans as they continue to shape the delivery system and the roles of providers.
Pharmacists would like to carve out a role for themselves in PGX testing. This is happening in leading health systems and academic medical centers that have expanded pharmacists’ roles, allowing them to order PGX tests and recommend changes in therapy.
Establishing a pharmacogenomics role for pharmacists in retail pharmacies is another story. Community pharmacists face a number of barriers that prevent them from ordering PGX tests or receiving the test results, which are key steps for them to incorporate PGX testing into their medication therapy management services.
A small demonstration project involving the University of North Carolina, Kerr Drug, and LabCorp tested the feasibility of community pharmacists playing the leading role in PGX testing.
“The study paired the Kerr Drug pharmacist with a supervising physician, and LabCorp agreed to perform the testing and provide test results directly to the pharmacist,” says Rebecca Chater, RPh, MPH, executive health care strategist at Ateb, a health care technology company. She was an executive at Kerr Drug during the demonstration project.
Physicians accepted the expanded role of pharmacists in dispensing the new therapies in a recent demonstration project, says Rebecca Chater, RPh, MPH, who was involved in the project.
The project enrolled 18 patients who were taking clopidogrel, a blood thinner. Clopidogrel was chosen because approximately 20% of patients have variations in their CYP2C19 gene that affect the ability of the CYP2C19 liver enzyme to convert clopidogrel to its active form.
“In the course of the pilot, the pharmacists ordered the genetic test, interpreted the results, evaluated the medication therapy, and as necessary they made recommendations to the prescriber for medication changes,” says Chater.
The final results shed some light on the role of community pharmacists in PGX testing. Test results for 9 of the 18 patients identified genetic variants that resulted in new therapy recommendations, and all of the recommendations were accepted by the prescribers.
“Throughout the entire study, we had no physician pushback,” says Chater. “In all cases, the pharmacists’ recommendations for medication changes were accepted by the prescribers.”
Pharmacists say they have the training and expertise to handle a central role in PGX testing. “The genetic information in the package insert is often very limited,” says Shanna O’Connor, PharmD, assistant professor at the University of Arizona. She was at the University of North Carolina at the time of, and was involved in, the demonstration project.
Insurers should consider granting provider status to pharmacists, says Shanna O’Connor, PharmD, who helped to test the feasibility of pharmacists playing a leading role in PGX testing.
“In some cases [the PI] will give you background information about the significance of a genetic variant, but actual medication decisions depend upon a pharmacist’s ability to connect the dots and combine that with other patient information to make a specific decision about therapy.
“Many drugs have more than one pathway for how the drug is processed,” she continues, “so if a genetic test indicates that one pathway is blocked, the drug still must be considered in terms of success of the other available pathway. This is something that pharmacists can be involved in, in terms of counseling patients and physicians.”
Despite this argument on behalf of pharmacists, there are substantial problems with implementing pharmacogenomics in community pharmacy. Some are technical, such as making test results available to pharmacy data systems through health information interchanges.
O’Connor says there are clinical and workflow concerns as well. “One of the next steps in seeing if pharmacists’ involvement in pharmacogenomics is feasible is to incorporate it into the dispensing process, and the barriers to that are huge.”
Pharmacogenomics will impose additional responsibilities on pharmacists. “If pharmacists have access to genetic information about patients and genes that are associated with drug interactions, then, ethically, they should be checking that information every single time a drug is this dispensed,” says O’Connor.
“The ideal situation for pharmacogenomic testing would be to check for gene and drug interactions in the same way that we do for drug-drug interactions or drug-allergy interactions.”
Decision support systems for gene interactions are just starting to be developed.
This extra step will add to the pressure for productivity that community pharmacists face. “Even if we make pharmacogenomics as streamlined as possible, it still adds an extra step to the dispensing process,” says O’Connor. “If this were done really efficiently, looking at a database or looking at a package insert to see what specific genetic information is available about the drug may add a minute or more to the process, but even one minute is a really long time in the dispensing process.”
She continues, “The current business model in community pharmacy is based on the number of prescriptions that are coming in, and the dispensing fee does not recognize the time that it would take for pharmacists to review genetic information and determine if action is necessary. In the current environment, there’s not a lot of incentive to expand pharmacogenetic testing into the workflow in community pharmacy.”
O’Connor says that the starting point for resolving many of the challenges of implementing pharmacogenomics in community pharmacy is for health plans to grant provider status to pharmacists.