A genetic test showing how people respond to common medicines has the potential to revolutionise the way doctors prescribe drugs. Business editor Maria Slade reports.  

Sleeping has never been my strong suit. Throughout my adult life I’ve tried everything from hypnosis and hot milk to yoga and the droning narrations of the History Channel, with varying degrees of success.

I’ve also tried drugs, of course, but doctors are generally pretty dark on handing out sleeping pills. After two decades of intermittent insomnia my GP and I have come to an understanding: he will give me melatonin for everyday use, and a tiny handful of Zopiclone in extreme circumstances, eg economy air travel.

Who would have thought cruciferous vegetables could upset that carefully balanced equilibrium? For it turns out I am an ultrarapid metaboliser of melatonin, a fast processor of the sleep regulating hormone, particularly if I smoke or eat a lot of broccoli and cauliflower.

I know this because I’ve had my DNA tested to see how I respond to a raft of common medicines. With the swab of a cheek Waikato-based Pinnacle Ventures’ myDNA test can detect how well I metabolise around 60% of the most regularly prescribed medications, including statins, antidepressants and anti-inflammatories.

Tests like myDNA are moving healthcare away from a one-size-fits-all approach and reducing the trial and error often associated with prescribing new medicines. The new tools have the potential to save the nation millions on the annual drugs bill, not to mention improve health outcomes.

Known as pharmacogenomics, the science is well established but the medical profession is only now starting to get on board with the benefits it can provide. While knowing to avoid too much broccoli when taking melatonin is a small outcome for me, for other people the ramifications of their genetic makeup can be far-reaching. Some antipsychotic medications fall into the same ‘CYP1A2’ gene category as melatonin which has implications for schizophrenic patients, Pinnacle Ventures’ medical director Dr Kerry Macaskill-Smith says.

“Most of them smoke, so you have to give them quite a lot of medicine to get it working. And if they quit smoking their medicine level is going to build up and possibly go to toxic levels. If we know this we can monitor you much more closely.”

Macaskill-Smith isn’t advising me to cut brassicas out of my diet. The key is my GP possessing the information about how I react to medications and being able to prescribe accordingly. Pinnacle Ventures is in the process of integrating myDNA with health records software programmes so that the test results can be sent directly to healthcare providers, for two important reasons: to protect patient information, and to prevent people from misinterpreting the results.

The myDNA test doesn’t look at any disease-risk genetic information, so it won’t tell you whether you might get cancer, for example. “I personally think that’s quite a good thing, because what do you do with that information?” Macaskill-Smith asks. It also won’t tell you whether you’re related to the British royal family or descended from vikings. It is specifically designed to look at your reaction to medicines, and the information isn’t used for anything else.

The test results follow a traffic light system – green for medications that will behave more or less normally in your body, amber for ones with minor prescribing considerations, and red where there’s more of an issue. My melatonin/broccoli sensitivity fell into the red category. Statins have an amber-level adverse effect on me, in that some brands are more likely to cause me muscle pain, and I also have a reduced response to opioid pain relievers which comes as no surprise given a family history of funny reactions to morphine.

Everybody’s got something, Macaskill-Smith says. “It’s very unusual for a person to get all the way through their report without having something they can take action on or something that would affect their future prescribing, we’ve found.” It can save six weeks to three months of mucking around trying to get a medication right, for instance with antidepressants where it takes a cycle to see how it works, she says.

“Once you’ve got a person’s genetic test you can treat them on the basis of their genetic profile and not on the law of averages. I can see a future where everybody has one of these tests done to help inform their future medications.”

Pinnacle Ventures is part of the Pinnacle Group, a network of primary and community healthcare provides across the central North Island. Ultimately its aim is to build up the body of data around the New Zealand DNA, and it is partnering with key iwi groups, Auckland and Otago Universities, and the government’s innovation agency Callaghan Innovation to develop a better understanding of how this country’s unique populations respond to different medications.

Auckland University pharmacogenomics expert Nuala Helsby says sending these test results directly to a health practitioner is the right approach.

“Your genes are just one part of the story, and there is so much more going on with everything that you interact with in your environment. The whole of that process is what anyone who’s prescribing has to think about all the time. It’s the art of medicine.”

Overseas, ancestry sites such as 23andMe also offer medical information, she says. “They will genotype you, and certainly in the States I believe they can give you a health report on that. The problem is it’s too broad; you need the nuance of having the medical practitioner sat with you taking everything else into account.”