Efficacy of Long-Term Opioid Treatment

Orlando—Patients with chronic non-cancer pain maintained reductions in pain for at least 6 months, according to a review of randomized, controlled trials, single-arm, open-label trials, open-label extension trials, and epidemiologic trials in which participants received long-term opioid analgesic therapy.

Results were presented at the AAPM meeting. The poster was titled A Literature Review on Efficacy of Long-Term Opioid Therapy.

The authors noted that chronic non-cancer pain is associated with a reduced quality of life and socioeconomic status. There are numerous options to treat chronic non-cancer pain, including opioid analgesics.

Before approving an opioid analgesic, the FDA requires the drug be tested in a randomized, placebo-controlled trial lasting 3 months. Thus, beyond 3 months, the efficacy of opioids is unknown.

Of the patients who begin taking opioids, only 2% to 20% remain on the drugs for up to 6 months, according to the authors. The authors mentioned that by examining the patients in trials who continue into open-label extension studies, they may be able to evaluate the efficacy of long-term analgesic treatment.

In this review, the authors searched for the terms “opioid,” “long,” and/or “therapy” using the MedLine, EMBASE, Biosis Previews, and PubMed databases through February 2013. They also reviewed articles through consensus statements, clinical guidelines, literature reviews, and meta-analyses.

When choosing the articles, the authors looked for the person-time exposed to opioid therapy, reported changes in pain from baseline to the end of study, changes in pain to baseline in 3-month intervals, and changes in the physical and mental components of the Short Form Health Survey.

The analysis included 60 studies: 8 randomized, controlled trials, 26 open-label trials, 12 open-label extension studies, and 14 epidemiology studies. The epidemiology studies represented 5415 patients and 4441 person-years of opioid treatment experience, while the other 46 trials represented 10,131 patients and 8463 person-years of opioid treatment experience.

Of the studies that lasted from 6 to 12 months, 83% had at least a 25% improvement in pain from baseline. Of patients that were at least 12 months, 82% had an improvement of at least 25% in pain from baseline.

In addition, of the 28 studies that reported pain scores over 3-month intervals, there was a large decrease in reported pain for the first 3 months, which was maintained through 6 and 12 months. Of the 9 studies that reported changes in mental component scores, 3 demonstrated a clinically significant improvement, while 5 of the 11 studies that reported changes in physical component scores demonstrated a clinically significant improvement.

There were a few limitations of the literature review, according to the authors. They noted that the studies varied in terms of the pain condition being treated, the severity of pain at baseline, and whether the patients were opioid-naïve when they entered the trials. They also did not take the quality of the studies into consideration and did not perform a meta-analysis. Finally, there were various instruments used to measure pain and functional status in the studies.

This study was funded by Purdue Pharma, L.P.