Medication adherence following pharmacogenomic testing in patients with major depressive disorder.

OBJECTIVE: Approximately 50% of patients with major depressive disorder (MDD) prematurely discontinue their antidepressant medication within 6 months, increasing risk of relapse. Pharmacogenomic (PGx) testing may improve medication adherence by informing treatment based on gene-drug interactions (GDI). Here, we evaluated whether PGx informed treatmentimproved medication adherence in MDD patients. METHODS: This was an observational, retrospective claims study of adult MDD patients who received a weighted multi-gene PGx test between 1 Jan 2015 and 30 September 2021 and switched medication. PGx results were linked with de-identified administrative claims data from the Optum Labs Data Warehouse. The PGx test report organized psychiatric medications into three categories: no known GDI (congruent), moderate GDI (congruent), and significant GDI (incongruent). Patients were assigned to the following groups based on the medication with the worst congruency 90 days pre- and post-PGx testing: incongruent-to-congruent, no-change-in-congruency, and congruent-to-incongruent. Medication adherence (proportion of days covered [PDC]) and discontinuation (a ≥ 45-day gap in medication fills) were assessed using pharmacy fill data during the 180 days following the date of medication switch (index date). RESULTS: Among 6224 patients with PGx testing, those in the incongruent-to-congruent group had the highest adherence (mean PDC 0.65, SD 0.33), compared to the congruent-to-incongruent (mean PDC 0.58, SD 0.34) (p < 0.05) and no-change-in-congruency groups (mean PDC 0.61, SD 0.34) (p < 0.05). The incongruent-to-congruent group also had the lowest discontinuation rate (46%) compared to the congruent-to-incongruent (55%) (p < 0.05) and no-change-in-congruency groups (50%) (p < 0.05). CONCLUSIONS: Using PGx informed medication selection can improve medication adherence and reduce discontinuation among MDD patients.