World-first study by Auckland scientists hopes to show genetic link to codeine addiction

Some people are “ultra-rapid metabolisers” of the opioid codeine. A team of Auckland University researchers believes they are also more likely to misuse the drug and become addicted. Tony Wall reports.

Amy Boatman was standing at a bus stop in Auckland when she saw an ad for Nurofen Plus, a painkiller containing codeine and ibuprofen which at the time was available over-the-counter at pharmacies.

She is from the US, where opioid products are prescription-only. “I was like, ‘oh my God, you can buy something at the pharmacy that’s an opiate? Holy s…’.”

Boatman had gotten clean after becoming addicted to a similar drug, hydrocodone, in the 90s, but had recently relapsed on alcohol and was vulnerable.

She bought some Nurofen Plus and took a couple of pills for the euphoric effect. Before she knew it, she was taking the whole 12-pack at once.

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“Then that wasn’t enough. They also sold them in a 30-pack – it got to the point where I was taking the entire 30 pills in one go.”

Boatman has always suspected she has a genetic propensity for addiction – “I come from a family of alcoholics and drug addicts” – and is intrigued by a study being launched by a team of Auckland University researchers looking at codeine abusers.

Unlike other opioids, codeine is a “prodrug”, meaning it is inactive when taken, but then modified by the liver to form morphine.

The amount of morphine produced depends on what type of liver enzymes the person has inherited – slow, intermediate or ultra-rapid.

Amy Boatman was addicted to codeine for many years but is now clean.


Amy Boatman was addicted to codeine for many years but is now clean.

Ultra-rapid metabolisers will get a much bigger shot of morphine from a dose of codeine than other people, likely giving them a high feeling.

The research team, led by Dr. Rhys Ponton of the university’s school of pharmacy, hypothesize that these people are more likely to develop problems with the drug.

By looking at the enzyme types present in people who misuse or are dependent on codeine, they hope to determine if this is the case.

In theory, it could help doctors know if a person is at risk of developing addiction or having an accidental overdose.

The research team is calling for volunteers who take codeine recreationally or who think they might be dependent on the drug to register for the study, which they say is a world-first. They will be asked to do a phone interview and provide a saliva sample by post.

Boatman says there is a lot of shame and stigma attached to opioid abuse, and it would be “amazing” if a genetic link could be proven.

“It would be great to be able to show that evidence to other people and be like, ‘look, I’m not morally bereft, there’s a natural, physical reason why’.”

Codeine was removed from over-the-counter sales, becoming prescription-only, in November 2020, due to concerns over abuse of the drug.

Legal opioid OxyContin maker Purdue Pharma has acknowledged its role in the opioid epidemic, paid $634m in fines and pleaded guilty to contributing to thousands of opioid deaths

But Ponton says only a small percentage of people – somewhere between 1 and 5% – are ultra-fast metabolizers of codeine.

If it can be shown that that cohort is the most likely to develop problems, he says, it would prove that there is only a small risk of selling codeine over-the-counter to the general public.

Ponton says that would remove the need for people to have to book appointments with GPs to access codeine, which, because of the cost, has created inequality in access to pain relief.

But Boatman says removing codeine from over-the-counter sales was a good move.

“The regulation around it was really lax. I could go into the same pharmacy once a week and get 30 pills. I would pharmacy shop – I would pretty much know where every single pharmacy in the … region is.

Boatman would take a whole box of Nurofen Plus at once.

Kevin Stent/Stuff

Boatman would take a whole box of Nurofen Plus at once.

“I like the idea of ​​a stronger pain medication being a little more accessible to people, but it just would have to have been better regulated.

“Putting the onus on the pharmacist to regulate it was too much, they’ve already got too much on their plate.”

Boatman’s abuse of codeine lasted for nine years, and she kept it a secret from her wife. She lost her job when it was discovered she was getting co-workers to buy codeine for her, and she became “unemployable”.

She has chronic stomach problems caused by the ibuprofen in the products she was taking.

Getting fired was the catalyst she needed to get clean, and in 2019 she returned to her family in Texas for three months.

“I was 51 years old, and I had to go back and live with my parents. It was the humbling experience that I needed.”

She did a 12-step program and is now sober.

“There’s a huge amount of shame. It’s like there’s another person in your body that’s doing these things – you just can’t stop yourself.”

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