Each of us metabolizes drugs in different ways because everyone has genetic variations.
For some, that can mean an otherwise effective prescription can pose unknown, even life-threatening risks.
Now, you can help protect yourself with DNA test kits that will tell you if you might have a genetic risk for certain diseases.
In April, the U.S. Food and Drug Administration (FDA) approved for the first time the direct-to-consumer marketing of a home DNA test kit.
Available from the company 23andMe, it allows consumers to test for 10 diseases, including Parkinson’s, Alzheimer’s, and some rare blood diseases.
A new era
Genetic testing and the flourishing field of pharmacogenomics — which studies how a person’s genes affect the way they respond to drugs, such as beta-blockers or statins — is making a revolutionary age of individualized medicine possible.
Dr. Richard Weinshilboum, whom some have called the father of pharmacogenomics, has been a pioneer in this field of research for three decades.
He’s also an internist, professor of medicine and pharmacology, as well as co-medical director of the pharmacogenomics program at the Mayo Clinic Center for Individualized Medicine.
“I work on cancer, and when you say genetic testing the public goes immediately to cancer,” Weinshilboum told Healthline. “But with pharmacogenomics, you’re talking about all of medicine.”
“The concept of pharmacogenomics is more than 50 years old,” he said, “and the whole idea of genetic diagnosis is one big mix master bowl. Genetic testing is the result of the Human Genome Project, and all of this research is a race to the starting line.”
Weinshilboum grew up in a small town in southern Kansas, where the town doctor, a general practitioner, lived next door.
“He gave most of his patients placebos and most of them got better,” he said. “Today, with DNA sequencing and pharmacogenomics, we’re entering the age of personalized medicine, where each patient will eventually receive the right drug at the right dosage.”
Although Weinshilboum’s work is with cancer, he said individualized medicine has the potential to benefit people with everything from diabetes to depression.
“The genomic revolution has immediate implications that will basically affect everyone everywhere,” said Weinshilboum.
His work focuses on three clinical goals: maximizing drug efficacy, selecting responsive patients, and avoiding adverse drug reactions.
Mother’s milk becomes deadly
Two dramatic cases involving a newborn baby and a woman illustrate the dangers of genetic variation and adverse reactions to drugs.
Weinshilboum cited a deadly 2005 case in Canada:
“A woman in Toronto delivered a normal baby boy, but the baby was not thriving. She had been prescribed Tylenol with codeine for post-delivery episiotomy pain. She breastfed her newborn, but he was not feeding well. Her baby died at 12 days old,” Weinshilboum recounted.
Codeine must be metabolized into morphine before it can begin to relieve pain, Weinshilboum said.
“Tests of the mother’s milk revealed she had a genetic variation that caused her body to create a greater than normal volume of morphine when it processed the codeine,” he said. “The morphine in her milk caused her baby to stop breathing.”
About 5 percent of women have this genetic defect. Women with this genetic abnormality who take codeine while breastfeeding expose their infants to high, possibly even toxic levels of morphine through their breast milk.
Medications produce serious heart condition
The other case occurred in 2009, when Karen Daggett of Minnesota and her husband, while visiting Florida, went on a Valentine’s Day date.
While on their date, she felt dizzy and nearly passed out. Prescription medicines she had been taking for an irregular heartbeat had accumulated in her body to a toxic level. She was rushed to an emergency room.
“I had been on various blood pressure meds and beta-blockers since my mid 30s and I’m 71 now,” Daggett told Healthline.
Daggett’s only warning came when she had ended up in the emergency room the year before.
“I had experienced milder symptoms as long as 40 years ago, but by the time I arrived at an ER, I would be back in normal heart rhythm, so nothing was documented or recorded,” she said.
Emergency physicians gave Daggett two additional medications, and she was placed in intensive care with a racing heart and extremely high blood pressure.
“They changed my meds again and within two days I was back in ER with the same symptoms, so they cut the drug in half,” she said. “I felt so miserable I went to Mayo Clinic, where I underwent a heart ablation in December 2008. [Ablation scars or destroys heart tissue that triggers or sustains an abnormal heart rhythm.] I was then put on the normal post-ablation medications, five of them, and joined a Lipitor [lipid-lowering statin] drug study.”
Daggett still “felt really weak and terrible,” but thought that was a temporary result of the surgery.
Then — back to that 2009 trip to Florida — Daggett was treated for four days without success and then taken to the Mayo Clinic where she underwent nine days of tests.
Her primary physician, Dr. Lynne Shuster, worked with her Mayo cardiologist, Dr. Hon-Chi Lee. They took Daggett off all meds and tried new ones that would be processed through her kidneys, not her liver.
Still, the physicians didn’t find any answers.
Then Shuster ordered pharmacogenomic testing, trying to discover if something in Daggett’s genetic makeup was affecting the way she processed medications.
“Dr. Shuster thought outside the box,” Daggett said. “They found an enzyme that metabolizes many, many drugs, including cardiac drugs, but was genetically missing in me. What a gift.”
Daggett’s family has since learned that 23 members of her family, covering four generations, have some variation of the liver enzymatic deficiencies, she said.
Daggett, who has been taking a safer heart medication since her genetic testing at the Mayo Clinic in early 2009, goes back for a yearly checkup.
Wherever she travels, Daggett carries with her a briefcase with her blood work files, in case she ever has to visit a physician.
“Most important is that I am alive to see two great grandbabies, and to share this information with others, in the hope that they can avoid the pain and fear I experienced,” she said. “I raised eight children and have 23 grandkids. I am hopeful that this pain has had a purpose. I am alive because of Mayo Clinic Research. For that I am forever grateful.”
The value of pharmacogenomics
Dr. Alan Wu, medical director of the pharmacogenomics lab at the University of California, San Francisco, educates physicians and students about the value of pharmacogenomic tests, and of performing clinical studies that demonstrate the value of this type of testing.
“We are currently performing a study on Plavix, an antiplatelet drug used after patients have undergone angioplasty,” he told Healthline. “Individuals who are poor metabolizers for this pro-drug have higher rates of restenosis [recurring abnormal narrowing of an artery or valve after corrective surgery] and myocardial infarction [heart attack].
“There is an alternate [on patent] antiplatelet drug that can be used, however it is costs more than Plavix,” he added. “Because individuals who are Asian or Pacific Islander have a much higher incidence of poor metabolism than Caucasians, this test is particularly relevant here.”
What are the limitations of pharmacogenomic testing?
The costs are considerably higher than for other types of clinical laboratory tests such as a complete blood count or a blood glucose exam, Wu said.
There are also privacy concerns for performing genetic testing.
Wu said pharmacogenomic testing refers to predicting the efficacy and toxicity avoidance of a particular drug on a particular individual.
“Because it does not diagnose genetic diseases, there is no stigma associated with testing,” he said. “It is akin to revealing that someone has a peanut allergy. The current limitation is convincing doctors to order these tests.”
Pharmacogenomic tests have another important use besides testing for heart disease, cancer, and depression.
Specialists are increasingly using the testing for pain management.
“Many of the medications used for analgesia are not effective for individuals who are poor metabolizers,” Wu said. “Other pharmacogenomics tests can be used for psychiatric patients on antidepressive medications. Newer tests are being discovered each year.”
Mayo Clinic involvement
The Mayo Clinic got involved in the test business in 2014, when it founded OneOme with Invenshure, a Minneapolis-based incubator and venture catalyst.
In the interest of full disclosure, Weinshilboum pointed out that he was one of the company founders, and that Mayo invested in the enterprise.
OneOme is a genomics interpretation company that uses Mayo’s considerable knowledge in pharmacogenomics. Their test, RightMed, is a take-home, physician-ordered analysis that sells for $249.
The test analyzes an individual’s DNA to predict their response to medications.
“OneOme can run the genotype test for sequence variants in several of the more common genes that can alter drug response,” Weinshilboum said. “The company also supplies a report for the physician that separates drugs into those the patient can take in the usual FDA-approved dose, and those that might not work, or which could result in an adverse reaction in that particular patient. But I should emphasize that the report is meant for the physician to use to treat the patient.”
The results of pharmacogenomics testing can be integrated into a patient’s electronic medical record.
“DNA does not change, so you don’t have to repeat the test,” Weinshilboum said. “The information follows patients wherever they go, and can serve as a lifelong resource for making effective prescription decisions.”