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Pharmacogenomics Fact Sheet

What is pharmacogenomics?

Pharmacogenomics (sometimes called pharmacogenetics) is a field of research focused on understanding how genes affect individual responses to medications. The long-term goal of pharmacogenomics is to help doctors select the drugs and dosages best suited for each person.

A little girl, a man and a woman
Your genes determine a lot about how you look. They also play a key role in how medications work in your body.

What role do genes play in how medicines work?

Just as our genes determine our hair and eye color, they are partially responsible for how our bodies respond to medications.

Genes are instructions, written in DNA, for building protein molecules. Different people can have different versions—slightly different DNA sequences—of the same gene. Some of these variations are common and some are rare. Some are relevant for health, such as those associated with a tendency to develop certain diseases.

Pharmacogenomics looks at variations in genes for proteins that influence drug responses. Such proteins include a number of liver enzymes that convert medications into their active or inactive forms. Even small differences in the genetic sequences of these enzymes can have a big impact on a drug’s safety or effectiveness.

One example involves a liver enzyme known as CYP2D6. This enzyme acts on a quarter of all prescription drugs, including the painkiller codeine, which it converts into the drug’s active form, morphine. The CYP2D6 gene exists in more than 160 different versions, many of which vary by only a single difference in their DNA sequence, although some have larger changes. The majority of these variants don’t affect drug responses.

Some people have hundreds or even thousands of copies of the CYP2D6 gene (typically, people have two copies of each gene). Those with extra copies of this gene manufacture an overabundance of CYP2D6 enzyme molecules and metabolize the drug very rapidly. As a result, codeine may be converted to morphine so quickly and completely that a standard dose of the drug can be an overdose.

On the other end of the spectrum, some variants of CYP2D6 result in a nonfunctional enzyme. People with these variants metabolize codeine slowly, if at all, so they might not experience much pain relief. For these people, doctors might prescribe a different type of pain reliever.

How is pharmacogenomics affecting drug design, development and prescribing guidelines?

The Food and Drug Administration, which monitors the safety of all drugs in the United States, has included pharmacogenomic information on the labels of more than 150 medications Link to external Web site. This information—which can cover dosage guidance, possible side effects or differences in effectiveness for people with certain genomic variations—can help doctors tailor their drug prescriptions for individual patients.

Pharmaceutical companies are beginning to use pharmacogenomic knowledge to develop and market drugs for people with specific genetic profiles. Studying a drug only in those likely to benefit from it could speed up and streamline its development and maximize its therapeutic benefit.

Additionally, if scientists can identify the genetic basis for certain serious side effects, drugs could be prescribed only to people who are not at risk for them. As a result, potentially lifesaving medications, which otherwise might be taken off the market because they pose a risk for some people, could still be available to those who could benefit from them.

How is pharmacogenomics affecting medical treatment?

Pharmacogenomics can help doctors pick the right treatment option and dose for each patient.

Currently, doctors base the majority of their drug prescriptions on clinical factors, such as a patient’s age, weight, sex, and liver and kidney function. For a small subset of drugs, researchers have identified genetic variations that influence how people respond. In these cases, doctors can use the pharmacogenomic information to select the best medication and identify people who need an unusually high or low dose.

What role does the National Institutes of Health (NIH) play in pharmacogenomics research?

For many years, NIH-funded scientists Link to external Web site have studied the effect of genes on medications relevant to a wide range of conditions, including asthma, depression, cancer and heart disease. The research findings are collected in an online resource of pharmacogenomic knowledge Link to external Web site.

NIH takes seriously the ethical and legal implications of pharmacogenomic research and works closely with researchers, clinicians and patient advocates to ensure the privacy of information from research participants and to maximize the benefits of pharmacogenomics research for individuals and society.

Furthering research and promoting the implementation of pharmacogenomics are important goals of NIH and are elements of a major initiative on precision medicine, which aims to tailor treatments based on each person's genes, environment, lifestyle and other characteristics.

NIGMS is a part of the National Institutes of Health that supports basic research to increase our understanding of biological processes and lay the foundation for advances in disease diagnosis, treatment, and prevention. For more information on the Institute's research and training programs, see

Content updated March 2015

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​Learn More

NIH Precision Medicine Initiative

FDA’s Unique Role and Responsibilities in Personalized Medicine Link to external Web site, U.S. Food and Drug Administration

Genetic Testing Registry is a single location to learn more about genetic tests, including those used for pharmacogenomics.

Expert groups such as the Clinical Pharmacogenetics Implementation Consortium Link to external Web site and the Clinical Genome Resource Link to external Web site are evaluating how to incorporate genomic results into medical care.

Other NIGMS Fact Sheets

This page last reviewed on October 18, 2017