What is pharmacogenomics and could it help you choose the right medication?

Two patients are prescribed the same medication. For one, the medication is extremely effective and does not cause serious side effects. But for the other patient, the medication is not effective at all or does cause significant side effects. For years, prescription medications were treated as essentially a one-size-fits-all solution, with drug choices and dosages based on the patient’s age, sex, weight, and, in some cases, their liver and kidney function, which affect how quickly a drug is metabolized (processed by the body). But researchers have learned that more and more medications are actually affected by the patient’s genetic makeup.

This field of study is known as pharmacogenomics. Simply put, pharmacogenomics is the study of how a person’s genes affect his or her response to medications. Each gene controls the production of a certain protein in the body. These proteins can be involved in how the body reacts to medications in several ways, including:

• How the body breaks down a drug
• How quickly or slowly the body absorbs a drug
• In some cases, the protein is the target of the drug

The goal of pharmacogenomics is to help doctors choose the most appropriate, safest, and most effective drug and dosage for each patient. Genetic information can tell doctors whether some drugs pose a higher risk of side effects or serious side effects, whether a higher or lower dose is needed for the drug to be effective, whether the drug won’t be effective or is more likely to be effective, and how long the drug should be taken to achieve the desired result.

To date, genetic testing is used for only a handful of medications. The FDA includes pharmacogenomic information on the labels of only about 150 medications, while the pharmacogenomics online resource and database PharmGKB, has catalogued 619 medications that are affected by gene variations, a fraction of the prescription drugs currently on the market.

How pharmacogenomics is being used today

Currently, genetic testing is being used for some medications used to treat breast, colorectal, stomach, and pancreatic cancer, and acute lymphoblastic leukemia. It’s also available for:

• the HIV medication abacavir, to determine which patients are at greater risk of serious side effects
• the blood thinners warfarin and clopidogrel, to help determine proper dosage
• several medications used to treat depression
• pain medications, including codeine, which can be metabolized too quickly and lead to an overdose in people with a certain gene variation
• some epilepsy medications
• the cholesterol lowering medication simvastatin, to determine the risk of side effects
• some medications that treat autoimmune diseases and prevent organ rejection after a transplant
• ACE inhibitors used to treat heart disease
• some asthma medications
• some arthritis and gout medications

If you’ve experienced severe or serious side effects from a medication in the past or taken medications that weren’t effective for your condition, you may want to ask your doctor if pharmacogenomic testing is available for the medications you need and whether it may be helpful for you. A health advisor may be another valuable resource who can provide you with more information about genetic testing and medications and connect you with specialists who are experienced with this testing.