Has a prescription from your doctor ever had unwelcome side-effects for you, like nausea, cold sweats or weight gain? Now imagine if you could avoid those side-effects. What if your doctor could know the best medication and dosage for your body based on your DNA? That’s the idea behind pharmacogenetics.

What is pharmacogenetics?

Pharmacogenetics is a health-science field that studies how our genes affect our reaction to medication. Dr. James Kennedy of the Tanenbaum Centre for Pharmacogenetics at the Centre for Addiction and Mental Health (CAMH) in Toronto says research in this innovative field can significantly improve healthcare.

“It is a much more informed way of deciding what medicine you are going to prescribe for a patient,” says Kennedy. Prescribing the correct medication is crucial when treating a mental illness, he says, because it generally takes 3 to 5 weeks for the effects of the medication to kick in. “Let’s say it took 3 tries to get the right medication. That patient could be suffering for 15 weeks or more, which is a very long time,” he says.

In partnership with Sun Life Financial and Assurex Health, a wholly owned subsidiary of Myriad Genetics, Inc., CAMH is studying how pharmacogenetics can improve mental healthcare. Now in its 5th year, the IMPACT (Individualized Medicine: Pharmacogenetic Assessment and Clinical Treatment) study has seen more than 9,000 patients take part so far. Kennedy hopes that in the future pharmacogenetic testing will be the new standard of care across Ontario, and beyond.

As of August 2017, Sun Life clients on approved mental health-related disability claims who are taking medication for their conditions can participate in the study. Patients use a cotton swab to provide a saliva sample, which goes to the CAMH labs where the IMPACT team analyzes it with Assurex’s GeneSight technology. This test indicates how a patient may react to 33 of the most widely used antidepressant and antipsychotic medications. An online results report then goes back to the patient’s doctor, typically in 36 to 48 hours.

The colour-coded report indicates the best treatment for the patient:

  • Green indicates that particular medicine is best-suited to the patient
  • Yellow indicates dosage levels of that medication may need to be adjusted
  • Red indicates that medication should be used with caution

How does pharmacogenetic testing work?

When you take medication orally, it first dissolves in your stomach, then is distributed through your bloodstream and absorbed by your liver. Exactly how your liver metabolizes the medication depends on your genes, because they determine the enzymes that metabolize chemicals in your body. Since your liver generally absorbs most chemicals when you take medication, the team at CAMH primarily tests the enzymes in a patient’s liver. “We measure from a genetic point how the liver breaks down or does not break down the common medications in Canada,” explains Kennedy. The same swab also lets the team test 2 genes affecting the brain as well as 6 genes affecting the liver.

Benefits of pharmacogenetic testing

  1. The harmful side-effects of taking the wrong medication are reduced.
  2. The stigma around taking medication for mental health illnesses decreases. Sometimes people are reluctant to take medication for mental illness due to the stigma associated with such medications. “There can be stigma against taking medication for mental health issues, so scientific backing that the medicine will be a good fit encourages people to try treatment,” says Nicole Braganza, program manager of the IMPACT study.
  3. Patients feel better faster. Kennedy says patients with depression saw a 27% reduction in the severity of their symptoms after 8 weeks of gene-guided treatment.
  4. Patients can go back to work and feel better at work quicker than with traditional treatment. “Through our partnership with Sun Life, we can examine how genetic testing benefits those who are missing work due to mental illness,” says Kennedy. At least 500,000 Canadians miss work weekly because of their mental health, according to CAMH.
  5. Health care costs decrease as patients make fewer trips to the doctor and/or hospital when they receive the correct medication on the first try.

Pharmacogenetics: The future standard of patient care in Canada?

The IMPACT study currently receives funding from Ontario’s Ministry of Research and Innovation. The researchers hope that once they complete the study some time in 2019, the data they’ve collected on the benefits of pharmacogenetic testing will spur the federal and provincial governments to increase their support for the technology. The team aims to submit its findings to the Ontario government to gain Ontario Health Insurance Plan (OHIP) funding for GeneSight testing.

More than 300 doctors have given their feedback on the genetic testing technology so far. Most have found the testing to be “helpful and easy to use,” says Kennedy. “They believe [pharmacogenetic testing] is going to be the standard in the future and that [in the future] every patient will receive this testing before a doctor prescribes medication."

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