Guest host Vicki L. Ellingrod, PharmD, talks with Kristen M. Ward, PharmD, and Amy Pasternak, PharmD, about integrating pharmacogenomic testing into psychiatric practice.

Dr. Ellingrod is senior associate dean at the University of Michigan College of Pharmacy, Ann Arbor, and professor of psychiatry in the medical school. She is also section editor of the savvy psychopharmacology department in Current Psychiatry. Dr. Ellingrod has no relevant financial relationships to disclose.

Dr. Ward and Dr. Pasternak are clinical assistant professors of pharmacy at the University of Michigan.  Dr. Ward and Dr. Pasternak report no relevant disclosures. Dr. Ward and Dr. Pasternak are team leads in the University of Michigan’s Precision Health Implementation Workgroup.

Take-home points

• Pharmacogenomics is defined as the study of the relationship between genetic variations and how our body responds to medications.
• Two common reasons for ordering pharmacogenomic testing are that a patient or clinician wants testing completed before starting the trial of a psychotropic medication and that there are concerns about nonresponse or loss of response to medications.
• Common insurance criteria used to justify such testing include at least one failed medical trial; future use of a medication likely to be affected by genetic variants, such as metabolism through CYP2D6 or CYP2C19; or identification of human leukocyte antigen (HLA) variants before starting carbamazepine or oxcarbazepine.
• Quality improvement and usability campaigns around pharmacogenomic testing include ensuring that testing results are readily available in the medical record.
• Results should be searchable.
• Alerts can be created for prescribers when they order a medication for which a patient has a relevant genetic variant.
• After ordering testing, clinicians should document the patient’s medication response genotype and phenotype in the medical record so the information can be used for medications other than psychotropics.

Summary

• Pharmacogenomic testing may be ordered for several reasons, including cases in which a patient or clinician wants information before switching to another medication or there are questions about failed medication trials.
• For approximately 50% of individuals who undergo pharmacogenomic testing, there may not be a change in treatment plans, or the results might not be conclusive enough to affect treatment. However, pharmacogenomic testing is useful in reassuring and improving adherence in patients who experience somatic adverse effects to psychotropic medications and want to know whether those effects are related to their metabolism.
• Getting insurance companies to cover pharmacogenetic testing can be tricky, and clinicians should be familiar with the criteria requested by insurers before ordering the tests. Many of the genetic-testing companies include a patient-assistance program to cover payment when insurance companies do not.
• In the medical record, it’s important to document the patient's genotype and phenotype. The patient’s genotype affects their metabolism of medications beyond psychotropics.
• Pharmacogenomic testing results can prevent serious adverse drug reactions. If testing comments on a patient’s carrier status for specific HLA subtypes implicated in drug metabolism, carbamazepine or other related medications should be added to the patient’s drug allergy list.
• States requirements about informed consent for genetic testing vary, so any clinicians who order such tests should be informed about their local laws.

References

Ellingrod VL. Current Psychiatry. 2019 Apr;18(4):29-33.

Deardorff OG et al. Current Psychiatry. 2018 Jul;17(7):41-5.

Ellingrod VL and Ward KM. Current Psychiatry. 2018 Jan;17(1):43-6.

Bishop JR. Current Psychiatry. 2010 Sep;9(9):32-5.

Maruf AA et al. Can J Psychiatry. 2020 Aug;65(8):521-30.

National Institutes of Health. National Human Genome Research Institute. Genome Statute and Legislative Database.

Clinical Pharmacogenetics Implementation Consortium. CPIC guidelines..

Pharmacogenetics Knowledge Base.

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Show notes by Jacqueline Posada, MD, associate producer of the Psychcast; assistant clinical professor in the department of psychiatry and behavioral sciences at George Washington University in Washington; and staff physician at George Washington Medical Faculty Associates, also in Washington. Dr. Posada has no conflicts of interest.

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