A Simple Genetic Test Could Significantly Cut Overdose Toll

By taking the guesswork out of prescribing medication, this simple test could help reduce the risk of overdose.

26 Oct, 2013


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A Melbourne geneticist has developed a test that can show if a patient is metabolising prescription drugs too slowly or too quickly. He says it could help reduce overdose deaths.

Associate Professor Les Sheffield said variations in particular genes were vital in determining how well a person processed medications but little testing was being done in Australia, prompting him to start such a service.

He developed myDNA to identify variations in four major liver enzyme systems that determine how quickly people process about half of commonly prescribed medications.

Patients provide a cheek cell sample using a swab and their test results are analysed by a pathology laboratory. A geneticist reports on whether the function of four key enzymes is reduced, normal or heightened.

The report details the medications processed by each enzyme, which include drugs for depression, anxiety and pain relief and blood-thinners.

an assortment of medications in and around a plastic container

It also makes recommendations – for example, if the function of an enzyme that processes codeine is reduced it is likely to provide limited pain relief and pose an increased risk of side effects, so an alternative is advised.

About 4500 patients have taken the $195 test since Professor Sheffield began offering it in 2010 through his company GenesFX Health.

Professor Sheffield said that being armed with knowledge about how well bodies processed medicines was important.

Nearly everyone was estimated to have an abnormal function in at least one of the relevant enzymes. Drug levels could build up in the blood of people who processed medications too slowly, placing them at risk of side effects, and people who processed drugs too quickly received little or no benefit from some medications, including anti-depressants.

Pamela Carmichael benefited from the myDNA test after experiencing serious side effects of various medications including antidepressants for decades.

”Doctors thought I was making it up,” she said.

”They can spend years trying to get the right drug and dose.”

Coroners Court figures show that prescription drugs contributed to the deaths of 304 Victorians last year, exceeding the state’s road toll of 282.

”If doctors and patients knew about how we metabolise drugs then maybe we could reduce the number of deaths,” Professor Sheffield said.

”You could also save a lot of money for the health system, because 7 per cent of all admissions to hospital are due to adverse drug effects.”

He said deaths had been reported in children who were ”ultra-rapid” metabolisers of codeine, which was converted to morphine in the body. Babies could also be poisoned by morphine in breast milk if their mother was an ultra-rapid metaboliser of codeine.

In addition to the myDNA test, Professor Sheffield is also conducting a number of clinical trials with major public hospitals in Melbourne to evaluate how gene testing can improve patient outcomes.

As seen in The Sydney Morning Herald

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