Major Finding: When opioids were used long-term for noncancer pain, 6%-23% of patients stopped taking them due to inefficacy or side effects and 0.3% developed signs of addiction.
Data Source: Cochrane Collaboration review of 26 clinical studies with 4,893 participants.
Disclosures: None were reported in relation to the review.
One of the first systematic reviews of data on long-term use of opioids found weak evidence to support the idea that adults who can take chronic opioids get chronic pain relief, though effects on function or quality of life are unclear.
In a Cochrane Collaboration review of 26 prospective studies with 4,893 participants, 6%-23% of patients (depending on the route of drug administration) dropped out of the clinical trials due to inefficacy or side effects, but those who finished the studies maintained clinically significant reductions in pain for up to 48 months, Meredith Noble and her associates reported.
The review also suggested that opioid abuse or addiction were rare, but acknowledged that the findings are compromised by the limited quantity and poor quality of the studies. Only 7 (0.3%) of 2,613 patients developed signs of addiction or took their medicine inappropriately in the studies that reported those outcomes (Cochrane Database Syst. Rev. 2010 [doi: 10.1002/14651858.CD006605
Most of the studies excluded patients with risk factors for abuse. The low rate of addiction may be generalizable only to patients with no history of abuse or addiction, wrote Ms. Noble, a senior research analyst at the Economic Cycle Research Institute, one of 14 evidence-based practice centers under the Agency for Healthcare Research and Quality. A previous study suggested that addiction or abuse may develop in 3% of patients in all studies of opioid use for chronic pain and in 0.2% of patients in studies that screened out participants with a history of abuse or addiction (Pain Med. 2008;9:444-59).
The evidence of long-term relief of noncancer pain with chronic opioid use was too sparse in the current review to draw firm conclusions, the investigators said.
Among 3,040 patients taking oral opioids, 23% discontinued treatment due to adverse effects and 10% dropped out because of insufficient pain relief. Among 1,628 on transdermal opioids, 12% stopped due to adverse effects and 6% stopped due to insufficient pain relief. Intrathecal pumps delivered opioids in 231 patients who could not find pain relief any other way; of these, 9% stopped due to adverse effects and 8% dropped out due to insufficient pain relief.
One of the studies in the review was a randomized trial comparing two opioids; the other 25 studies were case series or uncontrolled continuations of short-term trials of opioids for noncancer pain. None included comparisons with placebo or nonopioid therapies.
The only other systematic review of opioid use for chronic noncancer pain was a 2008 study by the same investigators.
Solid estimates are lacking for the number of people with chronic noncancer pain who are taking opioids long-term. Two U.S. studies suggest that 0.65% of people with medical insurance use opioids chronically.
However, two pain experts said in interviews they fear clinicians might read too much into the review's limited findings.
The report is “very encouraging, but it's far from the whole story,” Dr. Perry Fine said. Because there are no good substitutes for opioids on the horizon, physicians need to find ways to make long-term opioid use more effective and safe, he said.
Dr. Fine, president of the American Academy of Pain Medicine (AAPM) and professor of anesthesiology at the University of Utah, Salt Lake City, compared current use of long-term opioids for noncancer pain with the use of surgical anesthesia 20-30 years ago when it had significant morbidity and mortality. “That didn't stop us from doing surgical procedures when necessary, but it did motivate research and improvements.”
Primary care internist Dr. Roger Chou said that the 0.3% rate of addiction reported is “a little misleading, because it's based on pretty crummy data.” The review's findings on addiction, pain relief, and adverse events apply to very select groups of patients, not the more complicated cases that raise concerns for physicians considering long-term opioids.
Mainly, the review shows how little is known about prescribing long-term opioids, suggested Dr. Chou, of Oregon Health and Science University, Portland, and lead author of clinical guidelines on chronic opioids for noncancer pain by the American Pain Society and the AAPM. “We really don't have good quality, long-term data on this, which is scary because we're prescribing these medications so much,” Dr. Chou said.
Disclosures: Neither commentator is associated with the Cochrane review. Dr. Chou reported no conflicts of interest. Dr. Fine has been a speaker for Wyeth and an adviser for many pharmaceutical companies that manufacture opioids.