New Genetic Test Can Prevent Harmful Drug Events

In medicine, one size does not fit all. Two people who take the same medication may have very different responses.

Many factors influence a person’s response to medications strong evidence now suggests that our genes may also play an important role.1 Just as genes contribute to whether we will be tall or short, brunette or blonde, our genes can also determine how we respond to medicines, including common painkillers such as codeine, ibuprofen and diclofenac.

While standard doses of most medicines work well for most people, some medicines do not work at all in certain people or cause unnecessary and sometimes dangerous side effects.

It’s All About Avoiding Adverse Events

Figures from the Australian Centre of Health Research2 show that widespread pharmacogenomic testing could save the Australian Government $12 billion by avoiding hospitalizations caused by adverse reactions to medications and the purchase of ineffectual medications.

Now a unique test called DNAdose identifies variations in your genes that may affect the way you respond to medications for depression, anxiety, blood clots, pain relief, stomach conditions and breast cancer.

Liver Enzymes Hold The Key

DNAdose identifies specific variations in four major liver enzymes belonging to the cytochrome P450 family (CYP2D6, CYP2C19, CYP2C9 and VKORC1) that can be used by doctors to determine the right medicine and dose for these conditions.

The genetic mutations determine how quickly and effectively more than 50% of commonly prescribed medications.

Some Painkillers Can Be Ineffective – Or Dangerous

For instance, we know that 17-25% of the population do not process some medications fast enough and are prone to side effects. For other medications, such as codeine or tramadol for pain, these patients will receive no pain relief. And people who metabolise tranquillisers such as benzodiazepines too slowly are prone to toxicity, drowsiness and confusion.

Around one third of people process medications too quickly (ultrametabolisers) and those on antidepressants can receive little or no benefit. Patients on painkillers such as codeine, oxycodone and tramadol can metabolise these drugs to a strong pain reliever too quickly, resulting in sedative effects.

New Test Is Relevant For Women

The test also has specific relevance in the field of women’s medicine. For instance, codeine and its metabolites, including morphine, circulate in the serum of pregnant women and are secreted in human breast milk.

So women who are ultra rapid metabolisers may develop high concentrations of morphine in breast milk leading to dangerously high serum morphine levels in their breastfed infants.

For these women it would be preferable if they would treat severe and/or chronic pain with alternative analgesic medications that do not require the CYP2D6 enzyme for metabolism.

Also, women taking tamoxifen for years to try to prevent a treated breast cancer from returning can discover whether the drug will work or not. The tamoxifen and pain relief tests are both contained in DNAdose, but can be ordered separately.

Pharmacogenomics Is At Forefront Of Personalised Medicine

Pharmacogenomics is an exciting and rapidly developing area of personalised medicine and the one-off DNAdose test is one of the first practical applications of this science, already improving the lives of patients in Australia.

The simple cheek swab DNAdose test is available online at http://www.dnadose.com or by calling 1300 436 373, or through selected pharmacies. A blood test can also be ordered through your GP.

Last reviewed 26/Feb/2014

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A Prof Les Sheffield

Associate Professor Les Sheffield is a Melbourne-based clinical geneticist and a specialist in the clinical interpretation of molecular genetic tests. He is a pioneer of pharmacogenetic testing in Australia
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