Is Zocor affected by genetics?

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

Relevant genes: SLCO1B1

Zocor is affected by pharmacogenetics through the SLCO1B1 gene. Your genotype for this gene can change how your body processes Zocor, 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 Zocor

simvastatin affected by SLCO1B1

Affected by SLCO1B1 · CPIC, FDA · Strong evidence

Read the full simvastatin genetics guide →

Simvastatin phenotype recommendations

Published guidance from CPIC and FDA on how simvastatin should be dosed or substituted based on your SLCO1B1 phenotype.

Phenotype	What it means	Recommendation	Evidence
Increased Function SLCO1B1	Your genetics suggest normal handling of simvastatin, so standard dosing can be used.	CPIC Prescribe desired starting dose and adjust doses based on disease-specific guidelines. FDA Initiate therapy with recommended starting dose.	Strong
Normal Function SLCO1B1	Your genetics suggest normal handling of simvastatin, so standard dosing can be used.	CPIC Prescribe desired starting dose and adjust doses based on disease-specific guidelines. FDA Initiate therapy with recommended starting dose.	Strong
Decreased Function SLCO1B1	Your genetics suggest a higher risk of muscle-related side effects from simvastatin, so a lower dose or a different statin is usually recommended.	CPIC Prescribe an alternative statin depending on desired potency. Low-risk options: atorvastatin 10–20 mg, pitavastatin 1 mg, pravastatin 40 mg, rosuvastatin 5–10 mg. Moderate-risk options: fluvastatin 80 mg, pitavastatin 2 mg, pravastatin 80 mg. High-risk options (use with caution): lovastatin 40–80 mg, pitavastatin 4 mg, simvastatin 20–40 mg. If simvastatin is used, limit dose to <20 mg/day. FDA Consider lower doses. The risk of muscle injury is increased, especially at higher doses.	Strong
Possible Decreased Function SLCO1B1	Your genetics suggest a higher risk of muscle-related side effects from simvastatin, so a lower dose or a different statin is usually recommended.	CPIC Prescribe an alternative statin depending on desired potency. Low-risk options: atorvastatin 10–20 mg, pitavastatin 1 mg, pravastatin 40 mg, rosuvastatin 5–10 mg. Moderate-risk options: fluvastatin 80 mg, pitavastatin 2 mg, pravastatin 80 mg. High-risk options (use with caution): lovastatin 40–80 mg, pitavastatin 4 mg, simvastatin 20–40 mg. If simvastatin is used, limit dose to <20 mg/day. FDA Consider lower doses. The risk of muscle injury may be increased, especially at higher doses.	Strong
Poor Function SLCO1B1	Your genetics suggest a much higher risk of muscle-related side effects from simvastatin, so switching to a different statin is strongly recommended.	CPIC Prescribe an alternative statin depending on desired potency. Low-risk options: atorvastatin 10–20 mg, pitavastatin 1 mg, pravastatin 40 mg, rosuvastatin 5–10 mg. Moderate-risk options: fluvastatin 80 mg, pravastatin 80 mg. High-risk options (use with caution): lovastatin 40–80 mg, pitavastatin 2–4 mg, simvastatin 20–40 mg. FDA Consider a lower dose or an alternative cholesterol medication. The risk of muscle injury is significantly increased.	Strong
Possible Poor Function SLCO1B1	Your genetics suggest a much higher risk of muscle-related side effects from simvastatin, so switching to a different statin is strongly recommended.	CPIC Prescribe an alternative statin depending on desired potency. Low-risk options: atorvastatin 10–20 mg, pitavastatin 1 mg, pravastatin 40 mg, rosuvastatin 5–10 mg. Moderate-risk options: fluvastatin 80 mg, pravastatin 80 mg. High-risk options (use with caution): lovastatin 40–80 mg, pitavastatin 2–4 mg, simvastatin 20–40 mg.	Strong
Indeterminate SLCO1B1	The impact of your genotype on response to this drug is unknown.	CPIC + FDA Initiate therapy with recommended starting dose.	—
Not available SLCO1B1	The impact of your genotype on response to this drug is unknown.	CPIC + FDA Initiate therapy with recommended starting dose.	—

Sources: CPIC, FDA

The gene behind the guidance

SLCO1B1 Solute Carrier Organic Anion Transporter 1B1

SLCO1B1 is the transporter that moves statins into liver cells where they work. A common variant (called *5) reduces transporter function and leaves more statin circulating in the bloodstream and muscle tissue. That's directly linked to statin-associated muscle pain and, rarely, more serious muscle damage.

People with reduced SLCO1B1 function are at higher risk of statin myopathy, especially on simvastatin and high-dose atorvastatin. Dose reduction or switching statin usually resolves it.

See all drugs affected by SLCO1B1 →

Browse the full drug-class: Statins.

Related medications

Find out how your genetics affect Zocor

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.