Almost one in 10 people continue to use opioids three months after surgery new research shows, posing a risk of addiction due to misuse.

Conducted by the University of Auckland, the research analysed dispensing records for more than 260,000 hospital admissions between 2007 and 2019.

Opioids, such as codeine, tramadol, fentanyl, and morphine are normally dispensed after surgery to treat acute pain.

Associate Professor Amy Chan of the School of Pharmacy in the University of Auckland says in the United States, addiction to these drugs had reached 'epidemic' levels, leading to a surge in illegal sales, overdoses, and deaths.

"The university research comes as a United States government-backed briefing highlighted New Zealand as a country with a high risk emerging of fentanyl abuse.

"While we don't yet have an epidemic in New Zealand, as in the US, these findings should spark concern."

The study looked at patients who underwent surgery and were dispensed opioids after discharge, using dispensing records for more than 260,000 patients who were admitted to any New Zealand hospital between 2007 and 2019.

It found almost one to 10 patients, or 9.1 per cent, had persistent use of the drugs.

The research leader, pharmacy lecturer Jay Gong said weak opioids could still lead to dependency.

"[They could] carry additional risks for older people who are more susceptible to side effects, as their kidney function is often reduced, and it is important for processing these medicines.

"Other risk factors include surgical specialties, having other serious health conditions, smoking, and pre-operative use of certain medications."

Case-by-case reviews were important to assess the need for prolonged use of the drug, he says.

"Some of these patients maybe continue using it for very good reasons... because they may have complex recovery periods, maybe they have subsequently developed some other complex pain disorders...

"But we don't know that at this stage, so it is really important that the next step on the research asks what is this underlying cause of continued use of opioids beyond 90 days."

Gong says that getting non-opioid pain relief after surgery lowers the chance of relying on opioids for a long time.

Opioids use trending upwards in older people

The research also highlighted an increasing rate of opioid prescribing among older adults, particularly women and those over 85.

The study looked at health records for more than 800,000 people over 65, from 2007 to 2018.

Lead researcher from the School of Pharmacy at the University of Auckland Hoda Fahmy says opioid use in older adults can be problematic.

"Opioid therapy should only be considered when potential benefits are likely to surpass risks, where it should be prescribed with extensive monitoring and regular assessments to determine the need for continuation."

The research found that codeine is the most prescribed opioid, followed by tramadol.

Fahmy says codeine and tramadol were weak opioids, but those were still a cause for concern, especially in older adults.

"Weak opioids can still lead to dependency and carry additional risks for older people who are more susceptible to side effects, as their kidney function is often reduced, and it is important for processing these medicines."

More research is needed to understand the reason behind the increase of opioid prescriptions, she says.

"To discern whether the increase in opioid dispensing is a consequence of over-prescribing or reflects appropriate pain management practices and to establish evidence-based guidelines for the use of opioids in the older population."

-Rayssa Almeida/RNZ.