Does long-term opioid therapy reduce pain sensitivity of patients with chronic low back pain? Evidence from quantitative sensory testing.

Abstract

Long-term opioid treatment has been used extensively in treatment of chronic low back pain (cLBP) in the last decades. However, there are serious limitations to the long-term efficacy of opioids and related side effects. In this study we investigated whether long-term opioid treatment changes pain sensitivity of patients with cLBP. A prospective, nonrandomized, cross-sectional study. Multidisciplinary pain management clinic, specialty referral center, university hospital in Germany. Using quantitative sensory testing (QST), we compared the pain sensitivity of the low back bilaterally among 3 groups: 35 patients with cLBP undergoing a long-term opioid therapy (OP); 35 patients with cLBP administered no opioids (ON), and 28 subjects with neither pain nor opioid intake (HC). OP patients showed significantly higher bilateral thermal detection thresholds to warm stimuli on the back as compared to both ON (P = 0.009 for left low back, P = 0.008 for right low back) and HC subjects (P = 0.004 for left low back, P = 0.003 for right low back). Pain thresholds for cold and heat on the hand were similar in OP and ON groups; both showed, however, significantly reduced heat pain thresholds in comparison with HC participants (P = 0.012 for OP, P = 0.001 for ON). Factors such as age, sex, duration and dose of opioid intake, and self-reported pain intensity, but not depression and pain duration, correlated significantly with QST results. Limitations include small numbers of patients with heterogeneous opioid therapy and the nonrandomized observational nature of the study. The current study demonstrated that chronic opioid intake may only reduce the temperature sensitivity but not pain sensitivity measured by QST which is a useful tool in detecting characteristic changes in pain perception of patients with chronic low back pain after long-term opioid intake.