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Every day, thousands of Canadians take opioid painkillers for chronic pain. How many of them know that there is virtually no good scientific evidence showing those drugs are safe and effective when taken for extended periods?

That question has been ignored for too long.

Earlier this month, The Globe and Mail documented how the opioid epidemic is being fuelled in large part by inappropriate prescribing, despite a lack of evidence the drugs work for chronic pain. Federal Health Minister Rona Ambrose called on doctors to reduce prescriptions, while the heads of some medical regulatory colleges called for a collaborative approach.

Now, a high-level panel of U.S. experts is also highlighting the question of evidence for opioids as a chronic-pain treatment. They have produced a report that concludes, in no uncertain terms, that "there is insufficient evidence for every clinical decision that a provider needs to make regarding the use of opioids for chronic pain."

Opioids are a class of potent painkilling drugs that can be highly addictive and lethal, and include oxycodone, fentanyl and hydromorphone. For many years, opioids were used to ease the pain of people who were dying, going through cancer therapy, recovering from surgery or dealing with other severe, acute injuries. In the past two decades (thanks in large part to the introduction of slow-release formulations such as OxyContin and the heavy marketing that went with it), opioids have become a front-line treatment for chronic pain.

In that time, the number of Canadians who have become dependent on the drugs, suffered serious side effects and died from accidental overdoses has continued to climb. The federal government does not track annual opioid-related deaths, but in Ontario, the chief coroner's office says that the number of fatalities tied to those drugs reached 582 in 2012, up from 344 in 2008.

Some people feel better after taking opioids – they're very effective at relieving acute, short-term pain – and don't become dependent. But many others who take the drugs are at risk. That's because the body naturally develops a tolerance to opioids, which means the dose has to be increased in order to experience pain relief. Experts who study opioid drugs say that the higher the dose, the higher the chance of dependence, serious side effects and accidental overdose. (Opioids depress the respiratory system, which can cause people who take too much to stop breathing.)

The U.S. National Institutes of Health recently commissioned a workshop to assess what the research actually says about using opioids to treat chronic pain. In preparation, a group of experts combed through the research to summarize what is known about the long-term safety and effectiveness of opioids. They produced a study that concluded the evidence for long-term use "is very limited but suggests an increased risk of serious harms."

In other words, there's no good evidence showing these drugs work, but ample proof they cause other serious problems. Opioids also don't seem to help many people improve their ability to function on a day-to-day basis, which is a key reason for seeking chronic pain therapy in the first place.

Last month, the American Academy of Neurology became the first major medical organization to publicly state that opioids are ineffective at treating many types of chronic pain.

The report that came out of the NIH workshop blamed inappropriate opioid prescribing on a "dysfunctional" system that "promotes clinicians prescribing the easiest rather than the best approach to addressing pain."

Dr. Erin Krebs, core investigator for the Minneapolis VA Center for Chronic Disease Outcomes Research, in Minnesota, took part in the workshop.

"To me, the most concerning thing is that we really accepted a therapy as a standard without having research showing that it's effective or really giving us any kind of idea of what the balance of risks and benefits would be for a patient," she said. "I think that's shocking."

Unfortunately, chronic pain is largely misunderstood and overlooked, despite the fact that estimates suggest as many as seven million Canadians are living with it.

A survey of chronic-pain sufferers released Oct. 16 by the Canadian Pain Coalition found that nearly three-quarters of respondents are in pain for more than 12 hours every day and had to wait almost 18 months for a diagnosis. A 2009 study found that only one-quarter of 1 per cent of federal health research spending was dedicated to the study of chronic pain.

Despite the lack of evidence on efficacy and the plentiful proof of harm, many doctors and chronic-pain sufferers continue to defend the use of opioid drugs to treat long-term pain. One of their main arguments is that with so few good alternatives for treatment, opioids have to fill the void, even if they come with very real risks of side effects, addiction and potentially death.

That argument is hollow. Chronic pain sufferers need – and deserve – more research and better access to alternative treatments that can help them not only feel better, but take back their lives.