Understanding variation in metoprolol response: CYP2D6, drug interactions, and phenoconversion

Area of Science:

• Pharmacology
• Genetics
• Clinical Pharmacy

Background:

• Metoprolol, a beta-1 selective blocker, is frequently prescribed for various conditions.
• Individual variability in metoprolol's pharmacokinetics (PK) and pharmacodynamics (PD) is influenced by CYP2D6 genetic variations.
• CYP2D6 inhibitors can cause phenoconversion, altering metoprolol exposure and response.

Purpose of the Study:

• To review the combined effects of CYP2D6 genotype and inhibitor use on metoprolol PK/PD.
• To analyze how different strengths of CYP2D6 inhibitors impact metoprolol metabolism and clinical outcomes.

Main Methods:

• Literature search of PubMed, Embase, and Scopus.
• Identification and analysis of 17 relevant clinical studies.

Main Results:

• Strong CYP2D6 inhibitors (e.g., paroxetine, fluoxetine) increased metoprolol exposure up to 8-fold, causing phenoconversion in extensive metabolizers.
• Moderate inhibitors (e.g., mirabegron, amiodarone) increased exposure 2-3 fold, particularly in individuals with high CYP2D6 activity, and reduced heart rate and blood pressure.
• Severe adverse events like bradycardia and hypotension were observed with strong inhibitors, especially in patients with cardiovascular disease and reduced CYP2D6 function.

Conclusions:

• CYP2D6 phenoconversion is a significant, often underestimated factor in metoprolol response variability.
• Integrating phenoconversion assessment into clinical practice can optimize metoprolol pharmacotherapy and improve patient outcomes.