The figures showed the number of people dispensed prescriptions from community pharmacies, and exclude drugs given in hospital.
Oxycodone is traded under brand names OxyContin and OxyNorm.
The use of oxycodone, a strong painkiller and Class B controlled drug, has been the subject of debate in the medical community. It is a synthetic, opium-like drug which provides highly effective pain relief, particularly for short-term, severe pain, such as after surgery or an accident.
For some people, ongoing use of opioids - the drug family oxycodone is from - is the best option for relief from debilitating pain, allowing a chance to function with relative normalcy.
Despite opioids' medical benefits, many have addictive properties.
Northland DHB addiction medicine specialist Dr Alistair Dunn said: "We have worked really hard in Northland to reduce oxycodone and the results are a pleasing testimony to our efforts.
"However, rise in morphine use remains a concern.
"While stronger opiates are essential and very effective for acute pain they are not a good choice for chronic pain conditions."
Dr Dunn added: "Our hospital pain service has a great multi-disciplinary team approach but are struggling to cope with demand."
The Faculty of Pain Medicine of the Australian and New Zealand College of Anaesthetists said some patients were hesitant to take opioids out of fear of addiction, despite the majority of recipients not experiencing dependence.
"A groundswell of opposition to prescription opioids could be detrimental to the thousands of patients for whom they are effective," said Professor Milton Cohen, FPM's Director of Professional Affairs.
"It would be most unfortunate for those people who respond well to opioids if this option was thrown out because of the risks of misuse."
Northland DHB's associate chief medical officer Dr Alan Davis said there has been a coordinated effort to reduce oxycodone use across the region, and he said it's now used in a "much safer and appropriate fashion".
"One of the principle causes of high use of strong opioids in Northland is related to our rapidly ageing population... The older population is much more likely to be on stronger opioids than younger age groups," Dr Davis said.
However, Northland DHB had the second highest rate in the country of people aged between 25 and 64 prescribed strong opioids - 45 per cent higher than the national average. Between 65 and 79 years old it was 7.7 per cent higher, and 5 per cent lower for over 80 year olds.
Prescription opioid abuse was at the point of an "epidemic" in the United States, according to the Center for Disease Control and Prevention. More than 14,000 Americans died in 2014 from overdoses involving prescription opioids, and almost 2 million Americans were addicted. Methadone and oxycodone were the two most overdosed opioids.
However, the prescribing environment in New Zealand was vastly different and more tightly controlled than in the US, said addiction specialist and psychiatrist Dr Jeremy McMinn. He said New Zealand was unlikely to ever get to the level of harm seen in the US.
Dr McMinn said oxycodone was a "highly addictive" opioid when used regularly, and its use in New Zealand has been under scrutiny for almost a decade.
"I think the safeguards are greater here compared to the US. It's a less sensationalist story, but I think the structure of healthcare provision here allows for more considered prescribing, which is your strongest safeguard.
"That having been said, many addiction specialists and some pain doctors would be concerned about the rate at which oxycodone has been prescribed without what seems to be adequate consideration around day-to-day safeguards," Dr McMinn said.
"We've become opioid heavy in our prescribing."
