CYP2D6 and Bradycardia: In addition, patients who are prescribed β‐blockers often have comorbidities and are therefore treated with multiple drugs that may have a pharmacokinetic interaction with a subsequent change in drug concentration.15 This interaction has been shown with metoprolol and the SSRI fluoxetine (CYP2D6 inhibitor), which increase the concentration of metoprolol thus inducing bradycardia.16