Mayo Magazine

Pharmacogenomics — Personalizing your Prescription

Intuitively, we believe that the medications prescribed to treat our illnesses will make us better. And much of the time, that's just the way it works. But once in a while, a medication taken to cure what ails us makes us feel worse. This is known as an adverse drug reaction. And for years, physicians prescribing medications didn't know if you would be helped or harmed by a particular medication until you tried it.

Removing the guesswork

Now that picture is changing thanks to the practice of pharmacogenomics. As a science, pharmacogenomics is the study of how a person responds to (or metabolizes) a drug. With pharmacogenomics, researchers can examine the inherited variations of a person's genes to determine how that person is likely to react to a prescribed medication. This level of detail eventually will allow physicians to know whether a person will have a good reaction to a drug, a bad reaction to a drug or no reaction at all. Soon a simple and rapid deoxyribonucleic acid (DNA) test will help your doctor narrow the field of possible medications down to the one drug that will best help you.

The answer is in the genes

One true success story in the field of pharmacogenomics is the difference a simple DNA test has made for children fighting acute lymphoblastic leukemia, the most common childhood cancer. For many years, physicians didn't understand why the class of drugs used to treat this disease cured some children but killed others. Physicians knew that the children died because these drugs overreacted and destroyed healthy bone marrow in addition to destroying cancer cells. But they couldn't predict these reactions prior to giving the medication. Key discoveries made by Mayo Clinic Pharmacogenomics Researcher Richard M. Weinshilboum, M.D., and his colleagues some 20 years ago finally gave physicians the answers they were looking for, which lie in the genetic structure of the children being treated. Individual genes determined whether the medication given would be therapeutic or toxic. It was this discovery that began the era of pharmacogenomics.

Today, children being treated at Mayo Clinic for acute lymphoblastic leukemia are routinely screened to determine the appropriate level of medication needed to destroy their cancer.

Is there a difference between pharmacogenomics and pharmacogenetics?

• Pharmacogenomics refers to the general study of all of the many different genes that determine drug behavior.
• Pharmacogenetics refers to the study of inherited differences (variation) in drug metabolism and response.

The distinction between the two terms is considered arbitrary, and the two terms are used interchangeably.