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Experts say Ottawa's proposal requiring oxycodone to be tamper-resistant would give Purdue exclusive control over one class of opioids while doing little to address prescription painkiller abuse.

The federal government's proposed rules aimed at making oxycodone more difficult to abuse would force generic versions of the popular drug off the market, handing the company at the centre of Canada's prescription painkiller crisis a monopoly.

Health Canada unveiled draft rules in June that would require slow-release oxycodone to be tamper-resistant, making it more difficult to crush, snort or inject for a quick high. But medical experts say the measures do not address a major public-health problem: the overprescribing of opioids that has led to an epidemic of drug abuse and overdose deaths.

Canada ranks as the world's second-highest per capita consumer of opioids. In Ontario alone, more than 500 people die each year from opioids, exceeding motor vehicle deaths, according to the provincial coroner's office.

The medical experts question why Health Canada would not apply the proposed rules to all opioids. They also fear the rules could make doctors believe tamper-resistant oxycodone is safer, leading to more liberal prescribing of the powerful drug.

The manufacturer of OxyContin, the widely used brand-name version that was part of a wave of prescription drug abuse in Canada, stands to benefit the most from the proposed changes. Purdue Pharma withdrew OxyContin from the Canadian market in 2012 shortly before the drug's patent expired and replaced it with OxyNEO, a retooled pill that is harder to crush. That same year, the federal government approved six generic versions of OxyContin.

The proposed tamper-resistance rules would effectively shut Purdue's rivals out of the generic oxycodone market until 2027, when the last of the company's patents on its abuse-deterrent technology expires.

Meldon Kahan, a prominent addiction specialist, said the federal government's proposal to require oxycodone to be tamper-resistant would give Purdue exclusive control over one class of opioids while doing little to address the crisis.

"This will benefit Purdue," Dr. Kahan said. "They're going to be very happy that generic OxyContin is off the market."

Jim Keon, president of the Canadian Generic Pharmaceutical Association, said generic drug manufacturers would have to stop selling oxycodone, forcing consumers to buy the more-expensive brand-name version and creating a monopoly for Purdue.

For a generic drug to receive approval, a comparison by Health Canada must verify that it is equivalent to the brand-name version in every way. Unless generic companies prove in court that Purdue's patents are weak or invalid, Mr. Keon said, they would not be able to market equivalent tamper-resistant oxycodone until those patents expire.

"Even if the generic company can replicate the technology, it can't sell the product because it's blocked by the new patent," Mr. Keon said.

Health Minister Rona Ambrose defended the proposed rules, saying in an e-mail response to The Globe and Mail that her priority is "finding all ways possible to inhibit the abuse of opioids." Tamper-resistance, she said, is "just one measure in a suite of measures."

Ms. Ambrose said a planned three-year phase-in for tamper-resistant oxycodone would give generic makers time to reformulate their products, rejecting suggestions the proposed rules would give Purdue a competitive edge.

Craig Landau, chief executive officer of Purdue Pharma's Canadian operation, said other drug manufacturers could create their own tamper-resistant technologies.

"Our protection is of our own invention," Dr. Landau, an anesthesiologist and pain doctor, said in an interview with The Globe. "To suggest that with a single product we're cornering the market because of intellectual property is just false."

The medical experts criticize Purdue for the role it played in encouraging doctors to prescribe opioids. OxyContin became widely used to treat pain because it was marketed as less addictive than other opioids. (In the United States, Purdue Pharma LP and three executives paid more than $600-million in fines for misleading claims that the drug was less addictive and less likely to lead to abuse than other pain medications.)

"This was the most successful pharmaceutical marketing campaign in history, and it completely transformed physicians' prescribing habits," Dr. Kahan told a House of Commons committee examining prescription drug abuse last year.

David Juurlink, head of clinical pharmacology and toxicology at Sunnybrook Health Sciences Centre, said he finds it a "little bit distasteful" that the proposed tamper-resistant rules would give Purdue a competitive edge.

"The issue with opioids is doctors have been systematically misled about these drugs," Dr. Juurlink said in an interview. "They work nowhere near as well as we were told … and yet they have become the go-to therapy for thousands of patients and thousands of doctors."

Until the mid-1990s, opioids were primarily prescribed to people in debilitating pain, such as terminal cancer patients. That began to shift in 1996, when Health Canada approved Purdue's OxyContin, a slow-release drug designed to deliver relief over many hours. Doctors prescribed it for everything from backaches to fibromyalgia, and OxyContin quickly became a market leader in the burgeoning field of chronic pain management.

Between 2010 and 2014, prescriptions for opioids jumped 24 per cent to 21.7 million in Canada, according to figures provided to The Globe by IMS Brogan, which tracks pharmaceutical sales.

Even as the overall market for opioids has grown, Purdue's share has declined since it stopped selling OxyContin. The company accounted for 16 per cent of all opioid prescriptions dispensed by pharmacies in Canada in 2014, down from 20 per cent in 2010, the IMS Brogan figures show. Overall sales totalled $766-million in 2014, with more than three dozen drug companies marketing different types of opioids, including hydromorphone and fentanyl.

Medical experts are concerned the federal government's decision to target just oxycodone for tamper-resistance could pave the way for Purdue to market OxyNEO as less likely to cause addiction than other opioids. In the slow-release oxycodone market, Purdue is still the dominant player, accounting for 80 per cent of prescriptions dispensed in 2014. If the new rules become law and Health Canada gives Purdue the go-ahead to market OxyNEO as tamper-resistant, it would be the only such opioid sold in Canada for the foreseeable future.

"There is a potential concern that [Purdue] would … reassure doctors that this is a product which is not going to be abused or patients aren't going to get addicted to it," Dr. Kahan said. "This is exactly what Purdue did originally [with OxyContin]."

Purdue's Dr. Landau disputed that claim, stating the company is keenly aware it must avoid marketing tamper-resistant products as superior to others.

"The last thing we want is to have doctors believe they have to worry less about these medicines and actually prescribe more of them," Dr. Landau said. "That would be a horrendous unintended outcome."

Since he took over as president of Purdue Pharma Canada in September, 2013, Dr. Landau has been pushing the federal government to remove generic oxycodone from the market. According to federal lobbying records, he has asked that "generic oxycodone controlled-release tablets not be approved for sale in Canada." The records show that he met separately with the associate deputy minister at Health Canada and two senior officials in the Prime Minister's Office between February and May, 2014.

In June, 2014, Ms. Ambrose announced the plan to require oxycodone products sold in Canada to be tamper-resistant, reversing an earlier policy decision in November, 2012.

Health Canada was of the view in 2012 that evidence was insufficient that tamper-resistant formulations resulted in less abuse and noted in a news release that the product monograph for OxyNEO contains no claims that the product is harder to abuse. "There is no scientific evidence to date that would allow OxyNEO to claim that it is 'tamper-resistant,'" says the release, which has since been deleted from Health Canada's website. A Health Canada spokesman told The Globe the government is now moving ahead with the tamper-resistance measures because of "strong stakeholder support."

Ms. Ambrose said in a statement that the government is targeting controlled-release oxycodone – long-lasting versions of the painkiller – because it has a "well-established history" of abuse. The long-term goal is to apply the rules to other opioids, she said, but there is no timeline.

Chris Simpson, president of the Canadian Medical Association, said in an interview the narrow focus on oxycodone is a mistake.

"If you create a deterrent for one drug, then people just move to other drugs that don't have that technology," Dr. Simpson said.

Dr. Kahan, the addiction expert, co-authored an analysis published in the Canadian Medical Association Journal in June, warning tamper-resistant formulations are a "gimmick" because they would hinder only users who inject or snort drugs while ignoring the vast majority of individuals who become dependent after taking pills as directed by their doctor.

Dr. Landau acknowledges that tamper-resistant formulations are not a "silver bullet." But he said he is convinced that Purdue can dissuade abuse with a drug that is designed to be more difficult to manipulate.

"The overwhelming majority of drugs that fall into the hands of adolescents for misuse and abuse, with often tragic consequences, actually come from the medicine cabinets of legitimate patients," he said.