Metoprolol drug interactions
Pro Research Analysisby 
Searched over 200M research papers
Metoprolol Drug Interactions: CYP2D6 Inhibitors and Antidepressants
Metoprolol is primarily metabolized by the liver enzyme CYP2D6. Many drug interactions with metoprolol occur when other medications inhibit this enzyme, leading to higher levels of metoprolol in the body and an increased risk of side effects such as bradycardia (slow heart rate) and atrioventricular block 12.
Strong CYP2D6 Inhibitors: Paroxetine, Fluoxetine, and Bupropion
Paroxetine, fluoxetine, and bupropion are potent CYP2D6 inhibitors. When taken with metoprolol, these drugs can increase the amount of metoprolol in the body by four to six times, raising the risk of serious side effects like severe bradycardia and heart block 12. Most studies suggest that this combination should be avoided, or if necessary, metoprolol doses should be reduced and patients should be closely monitored for side effects 1278.
Moderate CYP2D6 Inhibitors: Citalopram, Escitalopram, and Duloxetine
Citalopram, escitalopram, and duloxetine are less potent CYP2D6 inhibitors. They can still increase metoprolol levels by two to three times, so dose adjustments and monitoring are recommended when these drugs are used together .
Antidepressants with Minimal Interaction
Sertraline, venlafaxine, mianserin, and mirtazapine have little or no effect on CYP2D6 and are not expected to cause significant interactions with metoprolol, making them safer choices for patients who need both medications .
Impact of Drug Interaction Databases
The implementation of drug interaction databases in clinical settings has led to a significant reduction in the co-prescription of metoprolol with strong CYP2D6-inhibiting antidepressants, helping to prevent potentially serious adverse effects .
Metoprolol and Other Drug Interactions
Metoprolol and Propafenone
Propafenone, an antiarrhythmic drug, also inhibits CYP2D6. When combined with metoprolol, it can increase metoprolol levels two to five times, leading to a higher risk of side effects such as hypotensive shock, nightmares, and heart failure. Dose reduction of metoprolol is recommended when used with propafenone 410.
Metoprolol and Apatinib
Apatinib, a cancer medication, can competitively inhibit the metabolism of metoprolol, leading to increased metoprolol levels and a greater risk of heart-related side effects. This effect may be more pronounced in males .
Metoprolol and Metformin
In animal studies, metoprolol decreased the plasma concentration of metformin by increasing its uptake into the liver, kidneys, and muscles. Long-term use of both drugs together led to higher levels of lactic acid and uric acid, which could be harmful .
Genetic Factors and Drug-Gene Interactions
People with genetic variations that make them poor CYP2D6 metabolizers can have up to five times higher metoprolol exposure, even without drug interactions. This increases the risk of side effects and may require dose adjustments .
Conclusion
Metoprolol is involved in several clinically significant drug interactions, especially with medications that inhibit CYP2D6 such as certain antidepressants (paroxetine, fluoxetine, bupropion) and antiarrhythmics (propafenone). These interactions can lead to dangerously high levels of metoprolol and serious side effects. Safer alternatives or dose adjustments should be considered, and close monitoring is essential when these combinations cannot be avoided. Genetic differences in CYP2D6 activity can further influence metoprolol levels and should be taken into account in clinical practice.
Sources and full results
Most relevant research papers on this topic