Ontario will become the first province to stop paying for high-dose opioid medications under its public drug plans, as part of a measure aimed at combatting the widespread abuse of prescription painkillers.

The Ministry of Health has posted a notice on its website saying all opioids that exceed the equivalent of 200 milligrams of morphine a day will be delisted from the province's drug formulary as of January. The ministry is overhauling its drug plans against a backdrop of rising addiction rates and overdose deaths across Canada.

"The inappropriate use, abuse and diversion of prescription narcotics has emerged as a significant public health and safety issue in Canada and other jurisdictions around the world," the ministry says in the notice advising physicians and drug manufacturers of the changes.

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The move comes after a Globe and Mail investigation found that Ottawa and the provinces failed to take adequate steps to stop doctors from indiscriminately prescribing highly addictive opioids to treat chronic pain. Ontario is the biggest per-capita user of prescription painkillers in Canada. In 2015, doctors wrote 8.1 million prescriptions for opioids, enough for nearly every person between the ages of 15 and 64 in the province, according to figures compiled for The Globe by IMS Brogan, which tracks pharmaceutical sales.

The over-prescribing of opioids is behind Canada's epidemic of painkiller abuse. By completely delisting the full portfolio of high-dose opioids in Ontario, ministry officials are acknowledging what medical experts have been saying for years: The risks associated with these powerful opioids are substantial and the benefits uncertain. Most other provinces and territories continue to list these opioids on their drug formularies either as general benefits or restricted access for cancer and palliative-care patients.

In 2014, the country's public drug programs spent $180.5-million on opioids, ranking them in the top 10 for spending on prescription medications, according to the Canadian Institute for Health Information. The programs typically pay prescriptions for those aged 65 and older and those on social and disability assistance. Just over 40 per cent of prescription drugs are financed by the public sector, with the remainder paid for by private insurance plans or individuals paying out of pocket.

Read more: Prescriptions of opioid drugs skyrocketing in Canada

Ontario's changes follow a review by a committee of the opioids funded by the province. The committee included physicians with clinical expertise in addiction, palliative care and pain management.

"I think it's a positive step but more needs to be done," said Meldon Kahan, medical director of the Substance Use Service at Women's College Hospital in Toronto.

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Dr. Kahan said he would also like the province to set a daily dose limit because physicians could simply replace the high-dose opioids with more tablets of a lower-dose version.

"Doctors prescribe high doses to the wrong people," Dr. Kahan said. "This remains a problem."

British Columbia's physician regulatory college recently unveiled the first mandatory standards in Canada for prescribing opioids, in response to a spike in the number of fatal overdoses linked to illicit fentanyl. The standards are modelled on new national guidelines in the United States for prescribing painkillers, which urge doctors to start patients with low doses of opioids and provide only a few days' supply.

Related: How B.C.'s fentanyl crisis became a public health emergency

Gordon Jones, head of the emergency department at Kingston General Hospital, said the department has a policy of not prescribing high-dose opioids or renewing lost or stolen prescriptions for painkillers.

"By far the vast majority of people who want these drugs are using them for illicit purposes," Dr. Jones said.

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The changes announced by the ministry target classes of opioids that have grown in popularity since 2012, when every province stopped funding the country's most widely prescribed painkiller. OxyContin, a brand-name version of oxycodone made by Purdue Pharma, was once the top-selling, long-acting opioid in Canada. But it became a lightning rod in the early 2000s as reports of addiction and overdoses exploded.

Purdue pulled OxyContin from the market in 2012 and replaced it with OxyNEO, a tamper-resistant alternative that is difficult to crush, snort or inject for a quick high. That same year, the provinces stopped paying for either opioid through their public drug plans. But by focusing specifically on those two drugs, medical experts said, policy makers missed the larger picture. Prescriptions for alternative, potentially addictive painkillers, including hydromorphone and fentanyl, rose sharply.

Ontario will no longer pay for 24- and 30-milligram capsules of hydromorphone, transdermal patches that deliver 75 and 100 micrograms of fentanyl per hour, and morphine in 200-milligram tablets.

Fentanyl was developed as a prescription painkiller but gained popularity as a street drug after OxyContin was removed from the market in Canada. OxyContin was popular not only with people who became addicted after their doctors prescribed it, but also with heroin users because it could be snorted like cocaine or injected like heroin for a quick high.

A palliative-care doctor who asked not to be named questioned whether the changes will do anything to address the fact that illicit fentanyl is behind many overdose deaths. He also said the changes could have an adverse impact on his patients who need high-dose opioids.

"Is this going to make a difference or is this just a knee-jerk reaction?" he asked.