DEAR MAYO CLINIC: Do genes have an effect on how medications work? My husband can take certain kinds of medicine without any trouble. But if I take the same thing, I feel groggy all day. Could that difference be somehow related to our genetics?
ANSWER: Your genetic makeup does have an impact on the way your body uses medication. There is quite a bit of existing research and more is currently underway in this area of study, called pharmacogenomics.
Everyone's body has a different way of processing, or metabolizing, drugs. That means everyone responds to medications in a slightly different way. For some people, a medication may work well with little or no side effects. For others, the same medicine may not work at all, or it may cause significant side effects. That happens for many reasons, including age, health and lifestyle. Research has shown that subtle differences in a person's genes also have an impact on medication metabolism.
Historically, it has been difficult for a doctor to tell who will be a good responder and who would be a poor responder to a specific medication before that person takes the drug. Through the power of genetics (studying a person's genes one at a time) and genomics (studying all of a person's genes at the same time), this is starting to change. For dozens of medications, performing a simple DNA test now can reveal whether or not a person is likely to do well with those medications.
For example, a drug called abacavir can be used to treat HIV. About 10 percent to 15 percent of the population has a gene mutation that can lead to severe adverse reactions if they take abacavir. AtMayo Clinic, if a doctor orders this drug, a warning appears on the computer immediately after the drug is ordered. It warns the physician that the patient should have genetic tests done before the patient begins taking the drug to ensure that he or she does not have the gene mutation.
Looking to the future, one day every patient's genome will be sequenced and this information will be in their medical record, just like other important health data. That way, rather than ordering one genetic test at a time, doctors and other health care professionals will be able to customize prescriptions and dosages to a person's genetic make-up quickly and easily because the information will be readily available.
Another promising area in the field of pharmacogenomics is the ability to make drug testing more efficient and cost-effective. Before a drug can be marketed in the United States, it goes through a rigorous testing process. It is likely that some drugs fail the process because some people enrolled in the trials to test the drug have genetic variations predisposing them to respond poorly to the drug, or not at all.
Researchers are exploring ways to identify genetic mutations that cause a person's body to inactivate a drug or cause harmful side effects. By identifying these mutations before testing begins, we can design better, more efficient trials and speed up the approval process. By designing drugs with pharmacogenomics in mind, more drugs will go on to be approved for use, with the understanding that certain people who have a particular genetic makeup should not use them. This is the goal of individualized medicine.
Although the field of pharmacogenomics holds significant promise and there have been success stories already, we're still in the early stages of the genomic revolution. Indeed, millions of genetic variations exist, and identifying them could take many years. This is a pivotal time, when researchers are learning more and more about the genomic basis of drug metabolism and response. That's leading to more situations where genetic testing can help determine the best medication for an individual patient. --Alexander Parker, Ph.D.,Center for Individualized Medicine,Mayo Clinic,Jacksonville, Fla.
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