Is rythmol SR affected by genetics?

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

Relevant genes: CYP2D6

rythmol SR is affected by pharmacogenetics through the CYP2D6 gene. Your genotype for this gene can change how your body processes rythmol SR, 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 rythmol SR

propafenone affected by CYP2D6

Affected by CYP2D6 · FDA · Strong evidence

Read the full propafenone genetics guide →

Propafenone phenotype recommendations

Published guidance from FDA on how propafenone should be dosed or substituted based on your CYP2D6 phenotype.

Phenotype	What it means	Recommendation	Evidence
Ultrarapid Metabolizer CYP2D6	Your body processes propafenone faster than most people, but there is no specific FDA guidance for your genotype. The standard dose is typically used.	FDA Initiate therapy with recommended starting dose.	—
Normal Metabolizer CYP2D6	Your body processes propafenone at a normal rate. The standard dose should work as expected.	FDA Initiate therapy with recommended starting dose.	—
Intermediate Metabolizer CYP2D6	Your body processes propafenone slightly slower than average, which can cause higher drug levels. This may increase your risk of irregular heartbeat.	FDA Use with caution. Monitor for heart rhythm changes due to higher drug levels.	Moderate
Poor Metabolizer CYP2D6	Your body breaks down propafenone much more slowly than normal, causing the drug to build up and increasing your risk of irregular heartbeat. This risk is even greater if you take certain other medications.	FDA Use with caution. Avoid use if also taking a CYP3A4 inhibitor. Monitor closely for heart rhythm problems.	Strong
Indeterminate CYP2D6	The impact of your genotype on response to this drug is unknown	FDA Initiate therapy with recommended starting dose.	—
Not available CYP2D6	The impact of your genotype on response to this drug is unknown	FDA Initiate therapy with recommended starting dose.	—

Source: FDA

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 rythmol SR

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.