Genetic testing targets medications
Study aims to give doctors new tool to make safer, more effective prescribing choices
Dr. Martin Dawes thinks patients deserve better when doctors are prescribing medications, starting with the safest, most-effective drugs based on a number of factors that would include patients’ genetic profile.
Dawes, the University of B.C.’s head of family practice, is asking 250 patients to submit saliva samples that will be tested for genetic aberrations that could affect the way they metabolize or react to medications. About 50 per cent of prescribed drugs aren’t effective because of patients’ genetic diversity, he said. Safety is also a problem, as Canadian studies have shown there are hundreds of thousands of serious, sometimes fatal, complications related to medications.
After genetic testing has been done on the study’s participants, their doctors will use a locally designed software program to help guide drug prescriptions for any of the common conditions the patients must have to enrol in the study: asthma, chronic obstructive pulmonary disorder, depression, epilepsy, gout, high cholesterol levels, high blood pressure, osteoporosis and osteoarthritis.
It is a proof-of-concept study that seeks to answer questions about personalized or predictive prescribing, as it’s called. Dawes believes that such testing (at a current cost of about $400 per patient) will actually save lives, given that about 10 per cent of emergency room visits stem from reactions to prescription drugs after doctors unwittingly select the wrong medication.
While factors like age, other medications being used, and allergies are taken into consideration when doctors are prescribing, Dawes said genetic makeup should also inform the choice. A UBC spinoff company called Gen-Xys, in which Dawes has a leadership role and financial interest, has developed the software program that will tell doctors in the study what medications they can prescribe.
Dawes won’t be surprised if some doctors snub the notion of collecting and charting yet more information for patient files.
“There will be resistance from some, I am sure, but there are always doctors who are receptive to innovations. This is meant to improve patient care and shorten the time it takes to select the right drugs.”
Dawes points out examples of drugs that benefit from genetic testing. One is codeine. Some patients have a gene variation that affects the way the pain drug is metabolized — taking it in the usual dose could depress respiratory rates dangerously. So those patients should either be prescribed a lower dose or something else.
A drug used f or gout, allopurinol, can cause potentially fatal skin and kidney reactions if used by Chinese or Korean patients who have a certain gene variant, he said. “There’s another drug that can be given if we know patients are hypersensitive because they have that variant, but it’s 10 times more costly,” he said.
Study participant Chris Phillips was once hospitalized for a severe reaction to a drug he took for a complex auto-immune disorder. “There are some pretty disturbing and alarming statistics about how the current shotgun, cookie-cutter approach to medication prescribing results in side effects and ineffectiveness,” he said. “I think this personalized prescriptive medicine approach has the potential to be exactly what I’m looking for.”
“I’m interested in pharmaco- genetics because I think it’s got the potential to revolutionize health care,” said Dr. Bryn Hyndman, a family doctor. “I see it as the future of medicine and the future of my career. And I think it will be especially important to use with fragile health populations, like elderly patients. It’s something that can expand our tool box when it comes to prescribing. And that’s important for family doctors because we write 60 per cent of the prescriptions.”
All costs related to the genetic sequencing of study participants in the $722,000 trial are covered. The three-month feasibility study is funded through grants from Genome BC and a few pharmaceutical companies. While a favourable trial may prompt researchers to ask the government to provide coverage for such testing, it is also possible the testing will be marketed directly to health consumers at an as-yet-undetermined cost.
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