03/12/2012 05:41 EDT | Updated 05/12/2012 05:12 EDT

Opioids after low-pain surgery: study indicates higher risk of dependency

TORONTO - The prescribing of painkillers to seniors for relatively low-pain surgeries may lead to some becoming dependent on opioids such as codeine or oxycodone, a new study suggests.

The study, published Monday in the Archives of Internal Medicine, found that 7.1 per cent of patients were prescribed an opioid within seven days of these low-pain surgeries, and more than 10 per cent of them were using these potent pain medications a year later.

The research set out to explore why older adults would start taking a strong morphine-like drug and whether the medical system could possibly be contributing to chronic use.

"What we're trying to do is identify how some of the older people might start it, and the idea is that some of the people might start it by just having a casual interaction with the health-care system for a fairly self-limiting illness," said Dr. Chaim Bell, senior author of the paper.

"From a patient perspective, do you really need to take the most potent pain reliever, do you need to even take it or to fill it? That's a patient perspective. From a physician's perspective, or from a system perspective, we really need to do a better job of tailoring or focusing the surgery and the patient's pain requirements."

In the study, Bell and colleagues from the Toronto-based Institute for Clinical Evaluative Studies and St. Michael's Hospital, also in Toronto, reviewed Ontario health data for 391,139 patients aged 66 and over who had one of four identified low-pain surgical procedures in the period from 1997 to 2008.

All the study subjects were described as "opioid naive" — they had not been prescribed opioids in the year before their surgery.

The procedures the researchers focused on were cataract surgery, gall bladder removal, surgery for benign enlargement of the prostate and varicose vein stripping. Bell said the four procedures are fairly low-pain and low-risk, and for most people, over-the-counter pain medication such as acetaminophen would probably suffice.

For the vast majority of these surgeries, the acute pain should have dissipated in the first couple of weeks, he said.

But a year after their surgery, 7.7 per cent of patients were being prescribed opioids. "More important, many individuals initially prescribed low-potency opioids had transitioned to more potent opioids, such as oxycodone, within one year of the surgery," the study said.

Bell said the research has probably identified a problem of a generic approach to post-operative care in which patients with higher pain scores are being lumped together with patients who don't have the same degree of pain, and don't necessarily require the same potent pain medicines.

And he said better communication is required between the hospital and primary care provider about how long patients should be requiring any of the medications after surgery, and whether the amount of pain reliever should be escalated.

Among those prescribed opioids within seven days of surgery, codeine was most commonly prescribed (93.4 per cent), and oxycodone was second (5.4 per cent). Among those prescribed opioids about a year after surgery, codeine was still the most commonly prescribed opioid — given to 87.5 per cent, but the share using more potent oxycodone had risen to 15.9 per cent.

In addition to concerns about addiction, opioids are commonly associated with adverse events such as sedation, constipation and respiratory depression, the study noted. And other recent work has suggested an association between long-term codeine use and risk of injury and adverse cardiovascular events among seniors.

Dr. Brian Warriner, head of the Department of Anesthesiology, Pharmacology and Therapeutics at the University of British Columbia, called the study valuable and said he's concerned by the results.

Warriner said it is unclear to him why patients getting a number of the surgeries listed should be receiving narcotics post-operatively at all.

"I can't imagine, for instance, that people having cataract surgery require narcotics, and I see that a high percentage of them are the ones that ultimately end up apparently getting it re-prescribed later on in the year, so I find that disturbing," he said in an interview from Vancouver.

"I think we're all concerned about the effects of prescribed medications on people, and this confirms that in people with really fairly minor surgical procedures, having relatively little pain, that we probably need to be much more careful in our use of these drugs."