Use of antidepressants with pharmacogenetic prescribing guidelines in a 10-year depression cohort of adult primary care patients.

OBJECTIVES: To describe the usage patterns of antidepressants with published CYP2D6- and CYP2C19-based prescribing guidelines among depressed primary care patients and estimate the proportion of patients taking antidepressants not recommended for them based on their CYP2C19 and CYP2D6 genotype-predicted metabolizer status. METHODS: Medication use and pharmacogenetic testing results were collected on 128 primary care patients enrolled in a 10-year depression cohort study. At each 12-month interval, we calculated the proportion of patients that: (1) reported use of one or more of the 13 antidepressant medications (i.e. amitriptyline, citalopram, escitalopram, clomipramine, desipramine, doxepin, fluvoxamine, imipramine, nortriptyline, paroxetine, sertraline, trimipramine, venlafaxine) with published CYP2D6- and CYP2C19-based prescribing guidelines, (2) were taking an antidepressant that was not recommended for them based on their CYP2C19 and CYP2D6 genotype-predicted metabolizer phenotype, and (3) switched medications from the previous 12-month interval. RESULTS: The annual proportion of individuals taking an antidepressant with a CYP2D6- and CYP2C19-based prescribing guidelines ranged from 45 to 84%. The proportion of participants that used an antidepressant that was not recommended for them, based on available CYP2D6 and CYP2C19 metabolizer phenotype, ranged from 18 to 29% and these individuals tended to switch medications more frequently (10%) compared to their counterparts taking medication aligned with their metabolizer phenotype (6%). CONCLUSION: One-quarter of primary care patients used an antidepressant that was not recommended for them based on CYP2D6- and CYP2C19-based prescribing guidelines and switching medications tended to be more common in this group. Studies to determine the impact of CYP2D6 and CYP2C19 genotyping on reducing gene-antidepressant mismatches are warranted.