CYP2D6 is an important pathway for the breakdown of certain medications. There are also some less common cases of medications that are prodrugs and activated by this enzyme. It is important to know some of these commonly used medications and how they may impact patient care. I would pay very close attention if you work with psychiatric medications as there are numerous psych medications that will be included in my list of drugs that inhibit CYP2D6.

Below is a list of drugs that inhibit CYP2D6. (Note: This is not a complete list, but my list of drugs that you commonly see used in practice)

Antidepressants That Inhibit CYP2D6

• Paroxetine
• Fluoxetine
• Bupropion
• Duloxetine (not as strong of an inhibitor as the other agents)

Miscellaneous Agents That Inhibit CYP2D6

• Mirabegron
• Terbinafine
• Quinidine
• Cinacalcet
• Darifenacin

Drugs Affected By Altered Metabolism

The two lists above are agents that inhibit CYP2D6. This is important to remember, but equally important to remember is which medications are metabolized by CYP2D6 into inactive and/or active metabolites. There are a few very important prodrugs that require activation by CYP2D6. Thus, when we reduce the action of CYP2D6, we ultimately reduce the effectiveness of these medications.

• Tamoxifen
• Codeine
• Tramadol

The following medications are likely to have their concentrations go up if a CYP2D6 inhibitor is used in combination. Medications that use CYP2D6 as a breakdown (deactivation) pathway include:

• Risperidone
• Some TCAs (such as amitriptyline, doxepin, nortriptyline)
• Clozapine
• Haloperidol
• Aripiprazole
• Brexiprazole
• Metoclopramide
• Metoprolol
• Propranolol
• Clozapine
• Paroxetine

Case Studies – CYP2D6 Drug Interactions

I’ve previously produced numerous case studies that demonstrate the importance of being aware of CYP2D6 drug interactions. Here are a few of my favorites if you’d like to do a little further reading.

Paroxetine – Tamoxifen Case Study

Bupropion – Fluoxetine Case Study

Terbinafine – Amitriptyline Case Study

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