The green light to Ranbaxy, India's biggest drug maker, came soon after Gil Kerlikowske, director of the White House Office of Drug Control Policy, reminded Health Minister Rona Ambrose of the dangers posed by generic forms of the opioid.
The U.S. has banned generic oxycodone because it's too easy for addicts to snort or inject, and only tamper-resistant forms of the drug can be sold stateside. American officials say the U.S. is dealing with a painkiller abuse epidemic that is killing tens of thousands of people a year.
The U.S. has been pressing Canada to outlaw generic oxycodone, citing studies that show the more addictive formulations are migrating south of the border.
Both countries are making progress in cracking down on addictive formulations of oxycodone, Kerlikowske wrote to Ambrose on Nov. 8, but "more can be done to prevent the misuse and diversion of generic oxycodone products, which remain available in Canadian markets in crushable forms."
He added: "We believe it is in the best interest of Canada and the United States to co-ordinate efforts around these issues, and we are eager to help facilitate ongoing dialogue with Canadian leadership and officials in the FDA and other U.S. agencies."
Neither Kerlikowske's office nor a spokesman for the health minister would say whether Ambrose replied to the letter.
But a spokesman for Kerlikowske, U.S. President Barack Obama's nominee to helm the powerful Customs and Border Protection Agency, said the U.S. and Canada have enjoyed a "productive" relationship on the issue that will hopefully continue under the new health minister.
Ambrose hinted last month she was looking into the issue of tamper-resistance and signalled the government would expand its national anti-drug strategy to encompass prescription drug abuse.
"Prescription drug abuse is a growing problem that we are working with provinces and territories to address," Ambrose said in a statement on Wednesday, adding the Conservatives are also attempting to tighten licensing rules that would help prevent the trafficking of addictive prescription drugs.
She didn't comment on why Health Canada bureaucrats are continuing to approve generic, addictive forms of oxycodone.
Health Canada, meantime, defended itself, saying it "rigorously" assesses every drug's safety and efficacy before approving it.
"These decisions are made by experts in the department based on science; the minister is not consulted on day-to-day drug approvals," said spokeswoman Leslie Meerburg.
She added Health Canada is working to help companies develop tamper-resistant opioid formulations that might help reduce the risk of abuse.
But Benedikt Fischer, a public health and addiction expert at B.C.'s Simon Fraser University, said the Health Canada decision makes no sense given the government is signalling its intention to crack down on generic oxycodone.
"To have more product available, in light of the fact that most provinces have deleted oxycodone from their formularies, is really contradictory," he said.
"We have policy measures where one side goes forward and the other side goes backward. It's completely weird — there's no consistent approach or strategy; it's a complete mess."
Amy Graves, a Halifax woman whose younger brother, Josh, died after taking a lethal combination of a prescription opioid and alcohol in March 2011, expressed dismay at Health Canada's decision.
"I am very disheartened," said Graves, who condemned the Health Canada approval process and accused the department of basing approval on clinical trials performed by the drug companies themselves.
"That's why these drugs get approved, because all information provided to Health Canada is from the drug makers. They're not getting information from an unbiased source. There should be some kind of independent study on these drugs."
It's not the first time there's been apparent conflict between Ambrose and Health Canada bureaucrats. In September, she slammed her own department's decision to provide heroin to certain addicts under a special access program, insisting it won't be allowed to happen again.
In 2010, for the first time, Canada inched past the United States to become the highest opioid-consuming country, per capita, on the planet. As many Ontario residents now die from opioid overdoses as they do in car accidents, according to a recent study by KFLA Public Health, based in Kingston, Ont.
Nonetheless, Kerlikowske's earlier appeals to Canada were rebuffed by Ambrose's predecessor, Leona Aglukkaq. The former health minister refrained from banning generic forms of the painkiller, instead directing provinces to deal with the problem.
Ontario, British Columbia, Saskatchewan, Manitoba and Prince Edward Island now only cover prescriptions for OxyNEO, the tamper-resistant version of the drug made by Purdue Canada — but that coverage generally only applies to senior citizens on social assistance.
The provinces have no control over what private health insurers will pay for, however, and most private insurers will cover drugs given the green light by Health Canada.