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How you respond to medicine might be in your genes

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April 7th, 2015
DNA strands
DNA strands

"Each year, about one million people are admitted to hospitals because of adverse drug events,” says Dietrich Stephan, Ph.D., professor and chair of the Department of Human Genetics at the University of Pittsburgh Graduate School of Public Health. “Roughly 100,000 people die because of these events. It’s a significant problem in the U.S.”

“Along with the health consequences, adverse drug events have cost our health care system billions of dollars,” says Daniel Schwarz, M.D., medical director of The Center for Pain Recovery in Southfield, Mich.  

Some adverse drug events might be avoided if personalized medicine was a routine practice in health care. According to the Food and Drug Administration (FDA), personalized medicine means tailoring medical care to a patient’s characteristics, needs, and preferences across the spectrum of care, including prevention, diagnosis, treatment, and follow-up.  A rapidly growing part of personalized medicine, however, is called pharmacogenomics, which means providing the right patient with the right dose of the right medicine at the right time—all according to their unique medical, environmental, and genetic information.

How it works

The same medication that’s effective for one person may not work for someone else. One person may experience side effects, while another doesn’t. These differences in responses could be due to health status, age, lifestyle factors, environmental influences, or any combination of these factors. But now scientists know that genes—specifically variations or mutations on certain genes—may also play a role. 

“Genetic testing can reveal how quickly someone can metabolize, or break down, a particular drug based on certain liver enzymes,” Stephan says.  For example, some people are genetically predisposed to metabolize certain drugs faster than the average person, causing them to have a stronger, more immediate response to medication. If they are taking several medicines that are metabolized by the same poorly functioning liver enzyme, it can result in too much of those drugs because they overload the system.” 

“Most people are familiar with genetic testing when it involves detection of genes related to diseases such as colon, breast, or pancreatic cancers,” Schwarz says. “But the results of genetic testing in the field of pharmacogenomics can guide a doctor in making informed decisions about prescribing medicines.”

Much of the time, collecting a specimen for this type of genetic testing is fairly simple and noninvasive. A device similar to a large cotton swab is rubbed against the inside of your cheek to collect cells. Most results are returned within two weeks. Blood tests are needed for some other types of genetic testing.

From theory to practice 

The practice of pharmacogenomics has been widely researched, tested, and implemented in a number of fields, including oncology, hematology, psychiatry, and cardiology. Tests look for genetic factors that affect chemotherapy drugs, antidepressants, and heart medications.

“The FDA recommends genetic testing for well over 100 drugs,” Stephan says. “If a particular drug has been shown to be affected by genetic variations, the FDA places that information on the label.”

“The people at highest risk, such as seniors and people with emotional disorders, are often prescribed a multitude of drugs with no insight into their genetic susceptibilities,” Schwarz says. “These are among the populations who are likely to benefit the most from genetic testing.”

Drawbacks

“This is a complicated field,” says Nathan Wei, M.D., director of the Arthritis Treatment Center in Frederick, Md. “Genetic biomarkers of disease are complex and numerous, which can make the development of targeted treatments more difficult than we once thought. This means some testing might be used before it has been proven effective.”

For example, doctors have been using genetic testing for a number of years to regulate the dosage of warfarin, a common blood thinner. But a recent large-scale study showed that this testing did not significantly improve physicians’ ability to determine therapeutic doses of warfarin. “Genetic testing is also very expensive,” Wei adds. 

Some experts believe that there are not yet enough ways to guarantee the confidentiality of people’s genetic information. “Despite the Genetic Information Non-Discrimination Act, there are loopholes,” Schwarz says.

“Today, it’s frightening to think about your genetic data being available to someone you don’t know who might discriminate against you,” Stephan adds. “But there are relatively few instances in which your information might be compromised, and even fewer cases of such information being used for a harmful purpose. Most of the time, the system works. But it can happen.”

In the pipeline

“There is a lot of research focusing on improving outcomes and reducing costs so that genetic testing can be broadly delivered to the general population and reimbursed by insurers,” Stephan says. “In the near future, genetic testing, especially for medication response, is going to be essential for seniors in order to maintain their health and wellness.” 

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