Long-term opioid treatment for chronic pain may carry risk for serious harm depending on the dosage, but evidence is minimal at best, a report from the Agency for Healthcare Research and Quality suggests.
The report sought to answer key questions about long-term opioid treatment in four categories: effectiveness and comparative effectiveness with nonopioids, harms and adverse events, dosing strategies, and risk assessment and risk mitigation strategies. In the report, which was based on the results of 39 separate studies, many key questions in all categories were unaddressed because of a lack of studies meeting inclusion criteria, and no key questions were addressed under effectiveness and comparative effectiveness. All but one that addressed a key question had low strength of evidence.
Dr. Roger Chou
Relevant studies for harms and adverse events found that rates of diagnosed opioid abuse ranged from 0.6%-8% and dependence rates were 3.1%-26% in primary care settings. Abnormal drug-related behavior rates occurred in 5.7%-37.1%. Long-term opioid treatment was associated with increased risk of abuse, overdose, fracture, myocardial infarction, and markers of sexual dysfunction. Higher doses also were associated with increased risk of those outcomes, reported Dr. Roger Chou and his associates at the Pacific Northwest Evidence-based Practice Center at Oregon Health and Science University, Portland, and the University of Washington, Seattle.
The report’s authors found very few studies relating dosing strategies to risk for serious harm. One study found that methadone had a lower mortality risk than did long-acting morphine in a veteran population, the opposite of what would normally be expected, according to the agency. Multiple studies showed that buccal or intranasal fentanyl was more effective in treating acute pain of patients who were undergoing long-term opioid treatment, but these studies focused on short-term outcomes only. No relevant studies could be found to answer key questions about risk assessment and mitigation strategies.
While evidence does point toward a dose-based increase in serious harm from long-term opioid treatment, “more research is needed to understand long-term benefits, risk of abuse and related outcomes, and effectiveness of different opioid prescribing methods and risk mitigation strategies,” the authors wrote.