Is Toprol XL affected by genetics?

Yes — the active ingredient is metabolized by a gene known to vary between individuals.

Relevant genes: CYP2D6

Toprol XL is affected by pharmacogenetics through the CYP2D6 gene. Your genotype for this gene can change how your body processes Toprol XL, which can affect both how well it works and how well you tolerate it. The strongest evidence level on this page is Strong, based on CPIC or FDA guidelines.

What's in Toprol XL

metoprolol affected by CYP2D6

Affected by CYP2D6 · CPIC · Strong evidence

Read the full metoprolol genetics guide →

Metoprolol phenotype recommendations

Published guidance from CPIC on how metoprolol should be dosed or substituted based on your CYP2D6 phenotype.

Phenotype	What it means	Recommendation	Evidence
Ultrarapid Metabolizer CYP2D6	Your body clears the drug very quickly, and we don't know if the usual dose will work well for you.	CPIC No recommendation for metoprolol therapy due to insufficient evidence regarding diminished metoprolol effectiveness clinically.	Optional
Normal Metabolizer CYP2D6	Your body processes the drug as expected; standard doses are likely to work well.	CPIC + CPIC + CPIC + CPIC Initiate standard dosing.	Strong
Intermediate Metabolizer CYP2D6	Your body processes the drug a bit more slowly, but no dose change is usually needed.	CPIC + CPIC + CPIC + CPIC Initiate standard dosing.	Moderate
Poor Metabolizer CYP2D6	Your body clears the drug very slowly, so you may need a lower starting dose and careful monitoring for side effects.	CPIC Initiate therapy with the lowest recommended starting dose. Carefully titrate dose upward to clinical effect or guideline-recommended dose; monitor more closely for bradycardia. Alternatively, consider selecting another beta-blocker.	Moderate
Indeterminate CYP2D6	The impact of your genotype on response to this drug is unknown.	CPIC Initiate therapy with recommended starting dose.	—
Not available CYP2D6	The impact of your genotype on response to this drug is unknown.	CPIC Initiate therapy with recommended starting dose.	—

Source: CPIC

The gene behind the guidance

CYP2D6 Cytochrome P450 2D6

CYP2D6 is the most clinically important pharmacogene. It metabolizes around a quarter of all prescription drugs, including many antidepressants, opioids, and stimulants. The gene is unusually variable: roughly 7 percent of people are poor metabolizers (they barely activate CYP2D6), and another 1 to 3 percent are ultrarapid metabolizers (their enzyme is overactive).

For most CYP2D6 drugs, poor metabolizers feel stronger effects and more side effects at standard doses, while ultrarapid metabolizers may feel almost nothing. For prodrugs like codeine, the relationship flips: poor metabolizers feel less effect because they can't activate the drug.

See all drugs affected by CYP2D6 →

Related medications

Find out how your genetics affect Toprol XL

This page describes the general pharmacogenetics. A Gene2Rx report analyzes your own DNA to tell you which metabolizer group you fall into, across every medication.

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Informational only — not medical advice. Pharmacogenetic guidance describes population-level patterns; your individual response depends on many factors. Never start, stop, or change a medication without talking to your prescribing clinician.