Assessing Practice Patterns of Antidepressant Medication and Tamoxifen Use Among Patients With Hormone...

Some commonly prescribed antidepressants inhibit CYP2D6, an enzyme that metabolizes tamoxifen into its active metabolite, endoxifen. This inhibition could theoretically decrease the efficacy of tamoxifen, which could hypothetically lead to higher breast cancer recurrence rates and mortality. There is inconsistent data reported on the potential drug-drug interaction between concomitant use of tamoxifen and CYP2D6-inhibiting antidepressants.

We investigated prescribing patterns of concomitant tamoxifen and antidepressant medications.

Our study population included adult women ≥ age 18, with stage 0-IV breast cancer who were treated at the Cleveland Clinic, received tamoxifen, and were concurrently prescribed at least 1 antidepressant medication. Patients diagnosed between 2016 and 2021 were identified from a tumor registry database. Among the 405 included patients, 74.8% were taking at least 1 antidepressant before initiating tamoxifen, while 25.2% were started on antidepressant therapy after beginning tamoxifen. Following tamoxifen initiation, 66.3% of patients who had been on an antidepressant continued with the same medication. Among those who switched antidepressants, 16.8% changed to a serotonin-norepinephrine reuptake inhibitor (SNRI), 12.8% changed to a different selective serotonin reuptake inhibitor (SSRI), and 2.6% changed to another class of antidepressant.

There is awareness of tamoxifen and antidepressant interaction among healthcare providers. However, differences in prescription patterns across providers exist. Individualizing care and, when appropriate, opting for antidepressants with weak or no CYP2D6 inhibition that are equally effective in treating mood disorders or other conditions may be important. While no adherence or outcomes data are presented here, a collaborative, interdisciplinary approach may help support consistent and effective oncologic and behavioral health patient care.