Naloxone Fails to Antagonize Initial Hypoalgesic Effect of a Manual Therapy Treatment for Lateral Epicondylalgia

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Abstract

Background

Recent research has shown that Mulligan’s Mobilization With Movement treatment technique for the elbow (MWM), a peripheral joint mobilization technique, produces a substantial and immediate pain relief in chronic lateral epicondylalgia (48% increase in pain-free grip strength).[1] This hypoalgesic effect is far greater than that previously reported with spinal manual therapy treatments, prompting speculation that peripheral manual therapy treatments may differ in mechanism of action to spinal manual therapy techniques. Naloxone antagonism and tolerance studies, which employ widely accepted tests for the identification of endogenous opioid-mediated pain control mechanisms, have shown that spinal manual therapy-induced hypoalgesia does not involve an opioid mechanism.

Objective

The aim of this study was to evaluate the effect of naloxone administration on the hypoalgesic effect of MWM.

Methods

A randomized, controlled trial evaluated the effect of administering naloxone, saline, or no-substance control injection on the MWM-induced hypoalgesia in 18 participants with lateral epicondylalgia. Pain-free grip strength, pressure pain threshold, thermal pain threshold, and upper limb neural tissue provocation test 2b were the outcome measures.

Results

The results demonstrated that the initial hypoalgesic effect of the MWM was not antagonized by naloxone, suggesting a nonopioid mechanism of action.

Conclusions

The studied peripheral mobilization treatment technique appears to have a similar effect profile to previously studied spinal manual therapy techniques, suggesting a nonopioid-mediated hypoalgesia following manual therapy.

Introduction

A number of systemic reviews have shown that manual therapy, the skilled application of manual forces to the joint structures, provides effective results in treatment of musculoskeletal pain.2., 3., 4. Much of the research of the neurophysiological effects of manual therapy has focused on spinal techniques and has implicated that mobilization-induced hypoalgesia does not involve endogenous opioid mechanisms.5., 6. This evidence arises from studies that have shown that manual therapy-induced hypoalgesia is not antagonized by naloxone,7., 8. fails to develop tolerance,[9] and occurs in the presence of normal plasma endorphin levels.10., 11. In addition to these findings, several studies of spinal manual therapy have indicated the specificity for techniques to produce mechanical but not thermal hypoalgesia,6., 12., 13. implicating endogenous noradrenergic rather than serotonergic mechanisms.[14]

Mulligan’s Mobilization With Movement (MWM) has been shown to exert a substantial and rapid pain-relieving effect in patients with chronic lateral epicondylalgia.1., 15., 16. It is a recently developed manual therapy treatment technique that involves the application of a sustained glide and active movement across a peripheral joint.[17] The role of endogenous opioid peptides in MWM-induced hypoalgesia has not been investigated and is the aim of this study. This study utilized a widely accepted test of endogenous opioid mechanisms, naloxone antagonism, to evaluate the role of such mechanisms in MWM-induced hypoalgesia.

Section snippets

Methods

This study utilized a randomized, placebo-controlled, crossover, double-blind, repeated measures design to evaluate the hypothesis that MWM-induced hypoalgesia was antagonized by naloxone.

Results

The MWM treatment technique produced a mean hypoalgesic effect of 29% (±5.6, SEM) in PFGS, 18% (±4.3) in PPT, 1.6% (±0.4) in ULTT2b, and 0.2% (±0.7) in TPT across all experimental conditions. Figure 1 shows the percentage changes of pain outcomes for each of the experimental conditions (naloxone, saline, control). There was no statistical difference between naloxone, saline, or control conditions (Table 2).

All 18 participants completed the study, and there were no adverse effects or

Discussion

The findings of this study showed that naloxone did not significantly antagonize the initial hypoalgesic effect of the MWM for the elbow when compared with a placebo saline injection or no-substance injection control. This result is similar to that of Zusman et al.[8] and Vicenzino et al.,[7] who found no effect of naloxone on spinal manual therapy-induced hypoalgesia, suggesting that the manual therapy may mainly induce a nonopioid form of analgesia as part of its effect.5., 7., 8.

The initial

Conclusion

The initial hypoalgesic effect produced by the MWM for the elbow was not significantly antagonized by pretreatment intravenous injection of naloxone, supporting the hypothesis that manual therapy-induced hypoalgesia most likely involves a nonopioid mechanism of action.

Acknowledgements

The authors are grateful to Dr Fiona Mack for performing the cannulations, injecting the substances, and randomly allocating the experimental conditions. The assistance of the participants in this study is also acknowledged.

References (35)

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Poster presentation in an abstract form of this study was made at the 10th World Congress on Pain of the International Association for the Study of Pain; August 17_22, 2002; San Diego, Calif.

This study was supported by funding from the Physiotherapy Research Foundation of Australia.

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