CYP2D6 Inhibition and Its Clinical Significance

Strong CYP2D6 Inhibitors

• Quinidine is a reference standard for potent CYP2D6 inhibition, affecting the metabolism of various medications, including antiarrhythmics such as propafenone and flecainide 1

Moderate to Mild CYP2D6 Inhibitors

• Sertraline, citalopram, venlafaxine, and escitalopram are considered mild CYP2D6 inhibitors, which is important when prescribing medications that are metabolized by CYP2D6, such as tamoxifen, as recommended by the National Comprehensive Cancer Network 2, 3
• Duloxetine is a moderate inhibitor of CYP2D6, which can impact the efficacy of medications like tamoxifen, and should be considered in clinical practice, as per guidelines from the National Comprehensive Cancer Network 2, 3

Clinical Significance of CYP2D6 Inhibition

• The American Heart Association, as published in Circulation, notes that CYP2D6 inhibition can affect the metabolism of antiarrhythmics, such as type 1C antiarrhythmics like propafenone and flecainide, highlighting the importance of considering CYP2D6-mediated interactions in clinical practice 1

Special Considerations in Clinical Practice

• The National Comprehensive Cancer Network recommends that when antidepressant therapy is needed in patients taking tamoxifen, mild CYP2D6 inhibitors like sertraline, citalopram, venlafaxine, and escitalopram are preferred over potent inhibitors like paroxetine and fluoxetine, due to their impact on tamoxifen efficacy 2, 3, 4
• Approximately 7-10% of the population are poor CYP2D6 metabolizers due to genetic polymorphisms, as noted in Circulation, which can impact the metabolism of various medications and should be considered in clinical practice 1