Tamoxifen Interactions with Psychiatric Medications

Mechanism of Interaction and High-Risk Medications

The American College of Oncology and the National Comprehensive Cancer Network recommend avoiding paroxetine and fluoxetine in patients taking tamoxifen, as they are potent CYP2D6 inhibitors that reduce tamoxifen's conversion to its active metabolite endoxifen, potentially compromising breast cancer treatment efficacy 1, 2, 3, 4
Bupropion and duloxetine are strong CYP2D6 inhibitors that should be avoided in patients taking tamoxifen, according to the National Comprehensive Cancer Network 4

The National Comprehensive Cancer Network suggests venlafaxine, citalopram, escitalopram, and sertraline as safe alternatives to strong CYP2D6 inhibitors, with minimal impact on endoxifen levels 1, 2, 3, 4
Desvenlafaxine and mirtazapine are also considered safe alternatives, as they do not inhibit the CYP2D6 enzyme 1, 2, 6

Gabapentin is a safe and effective alternative for hot flashes, with no CYP2D6 interaction, and can reduce hot flashes by 49-54% at a dose of 900 mg/day 1, 2, 6
Pregabalin is also a safe alternative for neuropathic pain and potentially hot flashes, with no CYP2D6 interaction 5

The National Comprehensive Cancer Network guidelines recommend reviewing all psychiatric medications immediately and switching to safe alternatives if necessary, to avoid compromising breast cancer treatment efficacy 3, 4
The NCCN guidelines explicitly state that coadministration of strong CYP2D6 inhibitors should be used with caution, and prescribers should consider alternatives with little or no CYP2D6 inhibition 3, 4
CYP2D6 genetic testing is not recommended by the NCCN guidelines for determining tamoxifen therapy, as drug-induced inhibition is easily avoidable through appropriate medication selection 3, 4