Non-pain-related factors—including previous use of pain medications, high perceived risk of addiction, and symptoms of depression—increase the risk of continuing to use strong pain-relieving drugs several months after surgery, reports a study in the September issue of Anesthesia & Analgesia, official journal of the International Anesthesia Research Society (IARS).
"Each of these factors was a better predictor of prolonged opioid use than postoperative pain duration or severity," according to the new research, led by Dr Ian Carroll of Stanford University.
Non-Pain Factors Predict Long-Term Opioid Use after Surgery
The researchers analyzed factors associated with long-term use of strong pain medications in 109 patients undergoing various types of surgery (breast cancer surgery, chest surgery, or joint replacement). Before their operation, the patients were evaluated for a number of factors potentially affecting use of pain medications.
After surgery, the patients underwent regular assessment of their use of opioid medications—morphine and related drugs. The goal was to identify preoperative factors that predicted continued use of opioids several months after surgery.
Five months postoperatively, six percent of patients still had a prescription for opioid drugs. Three factors were independently related to long-term opioid use, after adjustment for other factors. Patients who took opioids for pain relief before surgery—whether prescribed or otherwise—were 73 percent more likely to be still using these medications at follow-up.
Long-term opioid use was also higher for patients who, before surgery, rated themselves at increased risk of becoming addicted. For each one-point increase on a four-point scale of perceived addiction risk, the risk of long-term opioid use increased by 53 percent. Patients with symptoms of depression were also at increased risk: a 42 percent increase for every ten points on a standard scale (the Beck Depression Inventory).
These risk factors were better predictors of long-term opioid use than the severity or duration of pain after surgery. The same three factors were significant regardless of the type of surgery the patient had.
"As patients recover from surgery, they face an ongoing choice either to continue taking prescribed opioids or to stop opioids and undertake non-opioid pain treatment," Dr Carroll and colleagues explain. But few studies have looked at the factors influencing continued use of strong pain medications after surgery. In patients with chronic pain, opioid use is more related to psychological distress and substance abuse than to pain intensity.
The new study finds that long-term opioid use is also linked to non-pain-related factors in patients undergoing surgery. The researchers point out that, if there six percent rate of long-term opioid use applied to the average 17.6 million patients undergoing surgery each year, there would be 1.1 million new opioid users in the population each year.
Use of prescription opioid drugs has increased rapidly in recent years, including both legitimate use for pain treatment and drug diversion and recreational use. Dr Carroll and coauthors emphasize that some of the long-term opioid use in their study could have been legitimate—but the findings raise concerns about the "disconnect" between the non-pain-related risk factors and the reason (pain relief) the drugs are prescribed. The researchers call for further research to clarify the relationship been the three risk factors and the development of opioid abuse and addiction.
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