TORONTO - Almost two million Ontarians - or 14 per cent of the province's population - filled prescriptions for opioids in fiscal year 2015-2016, says a new report, suggesting that patients continued to be given the potent narcotics despite efforts to curtail what's been called a national epidemic of overuse.

The report by Health Quality Ontario, released Wednesday, found that more than nine million prescriptions for the powerful painkillers were filled between April 1, 2015, and March 31, 2016, the most recent fiscal year for which data is available. That figure represents an increase of 450,000 prescriptions over the same period three years earlier.

Not only did the number of prescriptions spiral upward, but there was also a trend toward doctors choosing more potent versions of the drugs, as well as a spike in the number of patients receiving the medications, said Dr. Joshua Tepper, president and CEO of the provincial agency.

"Despite people (being) aware of the significant impact and danger of opioids, we continue to see a steady increase in the number of prescriptions being written," said Tepper.

The report found there had been a shift to doctors prescribing stronger opioids over time. For instance, 29 per cent more patients received hydromorphone in 2015-16 than in 2013-14. The drug is five times more potent than morphine, the drug used in prescribing guidelines as a baseline standard for comparing the strengths of different opioids.

"Hydromorphone was a drug that a few years ago was very rarely used and now is being much more commonly prescribed," he said. "You may see greater dependency over time developing with lower-potency (drugs) and people shifting (to it) to deal with the tolerance that developed."

Addiction experts say another reason doctors switched to such opioids as hydromorphone, tramadol and morphine relates to the replacement of OxyContin in 2012 with OxyNeo, a tamper-proof version of the widely used drug that was subsequently delisted from Ontario's drug benefit formulary in a bid to curb excessive prescribing.

Tepper said the report also looks at the age breakdown of patients receiving opioid therapy and the length of their treatment.

For patients aged 18 and younger, two-thirds of prescriptions filled in early 2016 were for a short duration, he said. "But what's still striking is that one-third of people zero to 18 are getting ongoing prescriptions, which is still quite significant.

"Then you move to people who are 45 to 64. Only 20 per cent of those people who are getting opioid prescriptions are getting just a one-time, short-term (course). That means 80 per cent are getting repeat prescriptions."

That ratio widens even more for people aged 65 and older: the data show only 15 per cent received a short-term course of opioids, while 85 per cent had ongoing treatment with the medications.

"So to the degree that we understand there is a role for short-term opioids, that's not typically how we're seeing them prescribed," said Tepper, who is also a practising family physician. "That chronicity starts to lead into real issues of dependency.

"We're not sure why we're seeing these patterns and I think that the hope of our report is that people will start to take a really good look and try to understand within a given community what's happening ... and what are the options to change it."

Benedikt Fischer, a senior scientist at the Centre for Addiction and Mental Health in Toronto, said it's been known for well over a decade that opioids posed risks of dependence or addiction and that prescribing in Canada was disproportionate to their benefits for relieving chronic, non-cancer pain. Canadians are the second-highest per capita consumers of opioids in the world, lagging only behind the U.S.

"This report puts a bit of a more refined picture on that state of affairs. It describes a lot of important details," Fischer said Tuesday.

"What it doesn't tell us is: are the people who are getting these prescriptions - should they be getting these prescriptions or not? That's the next critical question that we really need to answer."

While the report points to such measures as greater access to the overdose-reversal drug naloxone and an increased emphasis on providing treatment for opioid use disorders, Fisher said the major driver of the opioid crisis - rampant oversprescribing - continues.

"So we've tinkered with prescribing and shifted a little bit from a rock to a hard place, but overall the general problematic situation of a high number of opioids being prescribed to a lot of people - and more often than not for a long term - remain virtually unaddressed," he said.

"That continues to be the main driver of the subsequent problems - misuse, diversion, dependence and an increasing number of people dying (of overdoses)."

Fischer said there's an "enormous systemic disconnect" between what researchers, physician regulatory bodies and government policy makers now know about the benefits and risks of opioids, based on a growing body of scientific evidence, and the continuing epidemic of excessive use.

"This isn't a trivial disconnect and we should have rectified it long ago because the knowledge has been out there for years."