The Pharmacist’s Value in Pharmacogenetic Testing for Mental Health

Pharmacy involvement in pharmacogenetics was not widely embraced when testing was first introduced. Some of the resistance may be attributed to the public perception of pharmacists in services beyond dispensing and the pharmacists’ own discomfort in offering these tests. Researchers assessing the perception of the pharmacist’s role have concluded that many patients are unaware of how pharmacists can be involved in direct patient care services.¹

Similarly, patients and health care providers may have limited knowledge regarding the benefits of pharmacogenetic testing. Numerous patients seek to find their ancestry history and risk of certain health conditions through direct-to-consumer genetic reports, but this rise in uptake has not been observed for pharmacogenetic testing. Clinical adoption of testing has also moved slowly, creating a barrier to educating both providers and patients on the value of both pharmacogenetics and the pharmacist’s role.

As medication experts, pharmacists can use their knowledge regarding drug-drug interactions to help providers select more appropriate medications for patients right from the start. Pharmacogenetic information gives pharmacists another tool for recommending ways to optimize drug regimens. Proper use of this information can help identify individuals who may not benefit from certain medications or may be at greater risk of adverse events and thus prevent these situations. Adverse drug events account for 1.3 million emergency department visits per year in the United States, contributing to hospitalizations and health care expenditures.²

Some pharmacists attribute the cost of pharmacogenetic testing as a barrier to uptake, but actually, the cost of currently available tests varies widely.³ Additionally, the number of genes included differs among pharmacogenetic panels. For example, some panels target genes relevant to certain disease states, such as mental health. To better appreciate the value of pharmacogenetics, consider the the process of selecting antidepressants. With antidepressants taking several weeks to produce the intended 

effect, patients undergoing treatment with standard trial-and-error prescribing may fail several therapies before finding an effective agent. Pharmacogenetic information can help prescribers select more appropriate agents for treating depression, and testing may soon reach a price point that is more reasonable for the general public. That said, routine adoption of testing requires evidence that it can be cost-effective.

Many studies have assessed the economic impact of pharmacog

enetic testing in the mental health setting. Fagerness and colleagues found that there may be a benefit to using pharmacogenetic testing in everyday psychiatric clinical practice because of improved patient adherence and decreased health care costs. This retrospective analysis compared 111 patients for whom pharmacogenetic testing was ordered with 222 controls who did not undergo testing. In four months, there was a total savings of $562 per patient for genotyped patients.⁶ This study is one of many that show a positive return on investment in pharmacogenetic testing in mental health. In the webinar “An Economic Evaluation of Pharmacologic Testing,” Josiah Allen assesses the cost-effectiveness of psychiatric pharmacogenomics. He notes that because many psychiatric medications interact with multiple pharmacogenes, part of the patient variability in drug response can be identified through pharmacogenetic-guided medication selection and dosing. Cost differences were compiled to compare treatment as usual in various mental health conditions with treatment with pharmacogenetic genotyping (

table 1

).⁴ 

Pharmacogenetic testing also has proven clinical value in the setting of mental health. The Clinical Pharmacogenetics Implementation Consortium guidelines for 2019, the gold standard for pharmacogenetic guidelines, include recommendations and actionable information for many medications used in the mental health setting.⁶ The most relevant genes affecting these medications include CYP2C19 and CYP2D6, and the associated guidelines can be observed in

table 2

. The guidelines include background on the genes, information on genetic interpretation of the tests, background on the drugs and therapeutic recommendations. These recommendations are specific to metabolizer status and will help determine whether medications are appropriate or if they 

should be dose adjusted or avoided. For example, the guidelines recommend that tricyclic antidepressants be avoided in CYP2D6 ultra-rapid metabolizers because of a potential lack of efficacy compared with normal metabolizers.⁷

Just as some pharmacists consider cost as an obstacle, others attribute their own knowledge as a barrier to implementing pharmacogenetic testing.³ That hurdle can be overcome. Clinical information on pharmacogenetics can be found on the package inserts for medications or through other resources, such as PharmGKB, a pharmacogenomics knowledge resource that summarizes clinical information.⁸ Pharmacists seeking to learn more about this area can pursue certification or train directly with pharmacogenetic lab companies that integrate pharmacists into the counseling process.

As their role has expanded to include clinical consultations, pharmacists can help identify and educate patients who might benefit from pharmacogenetic testing. By assisting in selecting patients and helping providers through medication recommendations, pharmacists can have a profound impact on patients. Additionally, potential exists to affect both clinical and cost outcomes for the health care system through pharmacogenetic testing. With the United States spending more on health care than most other countries, it is increasingly important to focus on cost-saving measures. Pharmacogenetic testing serves as a valuable tool for pharmacists and providers seeking to optimize drug regimens and improve the patient experience. The overall outcome for patients is greater treatment efficacy, fewer adverse events and drug interactions, and improved medication adherence.

References

• Bastianelli KMS, Nelson L, Palombi L. Perceptions of pharmacists' role in the health care team through student-pharmacist led point-of-care screenings and its future application in health care. Curr Pharm Teach Learn 2017;9(2):195-200.
• Centers for Disease Control and Prevention. Adverse Drug Events in Adults. Available at: https://www.cdc.gov/medicationsafety/adult_adversedrugevents.html. Accessed June 26, 2019.
• Irvin M, Bentley OS, Abubakar A, Rhodes LA, Marciniak MW. A Survey to Identify Barriers in the Implementation of Pharmacogenomics in Independent Community Pharmacies. Presented at: American Pharmacists Association Annual Meeting and Exposition; March 25, 2017; San Francisco, CA.
• Fagerness J, Fonseca E, Hess GP, Scott R, Gardner KR, Koffler M, et al. Pharmacogenetic-guided psychiatric intervention associated with increased adherence and cost savings. Am J Manag Care 2014;20(5):e146-56.
• Josiah Allen. 2019. An Economic Evaluation of Pharmacogenomic Testing. Seattle: Translational Software.
• Clinical Pharmacogenetics Implementation Consortium. Guidelines. Available at: https://cpicpgx.org/guidelines/. Accessed June 26, 2019.
• Hicks JK, Sangkuhl K, Swen JJ, Ellingrod VL, Müller DJ, Shimoda K, et al. Clinical pharmacogenetics implementation consortium guideline (CPIC) for CYP2D6 and CYP2C19 genotypes and dosing of tricyclic antidepressants: 2016 update. Clin Pharmacol Ther 2017;102(1):37-44.
• PharmGKB. About Us. Available at: https://www.pharmgkb.org/about. Accessed June 26, 2019.