DNA testing is used to predict a person’s response to drugs as part of a field known in the medical world as pharmacogenetics. It’s essentially personalized medicine that uses the unique blueprint of an individual’s genetics as a guide.
“Pharmacogenetics is a science that explores the interplay between our genes and how (an) individual’s body processes pharmaceuticals, hence the word pharmacogenetics,” said Veronika Litinski, CEO of GeneYouIn Inc. a biotechnology company in Toronto.
How it works
To better understand how pharmacogenetics works, let’s use coffee as an example. It contains the oh-so-beloved drug caffeine, which everyone’s body processes differently.
Some can drink it all day and have no trouble sleeping, while coffee may have the opposite effect on others. That’s because a person’s body breaks down caffeine either quickly or slowly.
“The same way as our DNA determines our personal characteristics — colour of our eyes or hair or body type — it also controls the way our enzymes work,” Litinski said.
“And for a particular pharmaceutical to be effective, it needs to be present in the bloodstream at a specific concentration so variations in DNA affect the enzymes that process medications.”
Enzymes in the liver are key, as they create chemical reactions in a person’s body. Depending on which enzymes a person has or doesn’t have, their reaction to a drug can be faster or completely dormant.
“Our livers are designed by our interactions over millions of years with poisonous plants and semi-poisonous plants and other kinds of toxins,” said Dr. James Kennedy, head of molecular science at the Centre for Addiction and Mental Health.
According to Kennedy, what people’s ancestors foraged has led to differences in how individuals metabolize drugs.
“It’s, in simplest terms, due to the very different diets that people had, say, in the Mediterranean basin versus in northern Europe or central Africa or in Asia,” he explained.
Although an individual’s DNA blueprint is a solid guide on which drugs are in the clear and which should be avoided, Kennedy says, other factors such as diet and lifestyle play an important role, too.
“The environment is always changing, and that’s the way life has always been so it’s this constant tension over millions of years of the body’s blueprint dealing with all the changes in the environment,” he said.
Kennedy believes the key in using pharmacogenetics is to work with that individual’s doctor and pharmacist closely to understand their DNA results and life choices and how those factors can alter a person’s reaction to drugs.
A life-saving science
Adverse reactions to prescription drugs are the fourth leading cause of death in the U.S. and cost the health-care system $136 billion annually. In Canada and the U.S. combined, adverse reactions kill more than 100,000 people a year.
In 2007, for example, a newborn at Toronto’s Hospital for Sick Children died due to morphine poisoning. Genetic testing later showed that the baby’s mother, who had been prescribed small doses of codeine following a painful childbirth, was an ultra-rapid metabolizer of the drug.
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“She didn’t know it, and none of the doctors knew it, that she was converting that codeine very fast to morphine, and that morphine was coming out in her breast milk to her innocent child,” Kennedy said.
Advocates of pharmacogenetic testing believe that if it was widely available, these kinds of cases could be avoided and deaths could be decreased significantly.
“In traditional prescribing, what happens is you’re given a standard dose. And then physicians, observe and, based on clinical presentation, they decide whether to increase the dose, reduce the dose, change medication so the whole process takes sometimes weeks, sometimes many weeks,” Litinski said.
“With the pharmacogenetic insights, we can leapfrog that phase of trial and error, figuring out, ‘What’s the optimal medication regimen for me?’”
Uncovering pharmacogenetic information
With the rise of direct-to-consumer DNA kits, which can be ordered online, individuals can now gain more insight into their own pharmacogenetic information.
Most kits provide a cotton swab for a saliva sample, which is then sent to a lab for analysis. Once a person’s sample is sent to a lab to extract their DNA, it is analyzed in an effort to match drugs with specific gene types.
A person’s body can metabolize medication either really quickly, which means it would have no effect, or very slowly, which means a person could experience an adverse reaction.
The point of this approach is to understand how a person’s body reacts to medication, and health-care professionals say it could reduce hospital visits and avoid adverse reactions.
With pharmacogenetic insight, scientists say they are trying to determine what the optimal drug and dosage is for a person based on the individual’s genetics. This could range from antidepressants to painkillers to cholesterol-lowering medications.
Litinski’s company offers a paid service that provides a report covering about 179 molecules, or roughly 70 per cent of all prescribed medications on the market.
Those results are then used by a health-care professional to understand which drugs are in the clear, which should be used with caution and which should be avoided.
“It’s really important because it’s very useful information; your genetics don’t change,” said Stacey D’Angelo, co-founder and pharmacist with Wellth.
“Knowing this information on how you might respond to medication before you start it can be really useful in managing your care and avoiding side effects and making sure you’re on the most effective drug for your body.”
The future of medicine
Though this way of prescribing medication is far from mainstream yet, pharmacogenetics actually dates back to the 1950s, when University of Toronto Prof. Werner Kalow was a pioneer in researching how genetic variations affect the way we metabolize drugs. He is considered one of the founding fathers of pharmacogenetics.
“Pharmacogenetic is an established science, but it’s still very new in practice and, like any new thing in health care, takes a while to bring together both knowledge of clinical practitioners, how to use it but also the infrastructure to make it really easy to use in practice. And also financial reimbursement,” Litinski said.
As of now, most people have to pay out of pocket to get a DNA test from a private company that provides pharmacogenetic insights. It’s also not guaranteed you’ll find a health-care professional that will know how to interpret the results.
“Most physicians and pharmacists who graduated maybe in the last five, seven years, they are probably very aware of genetics. But physicians, practitioners who went to school maybe 20 years ago, it was just not part of the education,” Litinski said.
However, she believes the approach of prescribing drugs based on a person’s age, weight and symptoms could soon be considered archaic. Instead, Litinski believes the future lies in understanding exactly how a person’s body metabolizes drugs before they take any medication.
Kennedy agrees that the field of pharmacogenetics has a role to play in prescribing drugs in the future.
“It’s new information that’s tested via saliva or blood and it’s a kind of a small revolution in the way doctors will write prescriptions in the future,” he said.
“It will likely become the gold standard in the future, to understand the patient’s individual makeup and personalize the prescription.”