Cyclobenzaprine for the treatment of myofascial pain in adults Stable (no update expected for reasons given in 'What's new')

Abstract

Abstract Background

Myofascial pain (MP) is a painful condition characterized by pain transmitted from trigger points (TP) within myofascial structures (in the muscles), local or distant from the pain. TPs can produce a characteristic pattern of irradiated pain or autonomic symptoms when stimulated. Cyclobenzaprine, a muscle relaxant that suppresses muscle spasm without interfering with muscle function, is used in clinical management of MP to improve quality of sleep and reduce pain.

Objectives

To assess efficacy and safety of cyclobenzaprine in treating MP.

Search methods

The Pain Palliative and Supportive Care Review Group's Specialised Register, CENTRAL, PubMed, EMBASE, LILACS and Scielo were searched in February 2009.

Selection criteria

All RCTs and quasi‐RCTs reporting use of cyclobenzaprine for treating MP with pain assessment as a primary or secondary outcome.

Data collection and analysis

Two review authors independently screened studies identified, extracted data, assessed trial quality and analyzed results.

Main results

We identified two studies with a total of 79 participants. One study, with 41 participants, compared cyclobenzaprine with clonazepam and with placebo. Participants taking cyclobenzaprine had some improvement of pain intensity compared to those on clonazepam, mean difference (MD) ‐0.25 (95% CI, ‐0.41 to ‐0.09; P value 0.002) and placebo, MD ‐0.25 (95% CI, 0.41 to ‐0.09; P value 0.002). The other study, with 38 participants, compared cyclobenzaprine with lidocaine infiltration. Thirty days after treatment there were statistically non‐significant differences between comparison groups, favoring lidocaine infiltration, for the mean for global pain, MD 0.90 (95% CI ‐0.35 to 2.15, P value 0.16), and for the mean for pain at digital compression, MD 0.60 (95% CI ‐0.55 to 1.75, P value 0.30). There were no life‐threatening adverse events associated with the medications.

Authors' conclusions

There was insufficient evidence to support the use of cyclobenzaprine in the treatment of MP. We identified only two small studies in which a total of 35 participants were given cyclobenzaprine, and it was not possible to estimate risks for benefits or harms. Further high quality RCTs of cyclobenzaprine for treating MP need to be conducted before firm conclusions on its effectiveness and safety can be made. Experts in this area should elect cut‐off points for participants to identify whether a patient has achieved a clinically relevant reduction of pain (primary outcome), so that their results can be combined easily into future versions of this review.

Author(s)

Frederico MG Leite, Álvaro N Atallah, Regina El Dib, Eduardo Grossmann, Eduardo Januzzi, Regis B Andriolo, Edina MK da Silva

Abstract

Plain language summary

Cyclobenzaprine drug treatment for myofascial pain in adults

Myofascial pain (MP) is a painful condition of the muscles characterized by pain transmitted from trigger points (TP) within connective tissue surrounding and separating muscles (myofascial structures). TP can be located where the pain is felt, or can be at a distance from it. Cyclobenzaprine, one of the drugs used to treat MP, is taken as a pill. It is a muscle relaxant, particularly used to improve quality of sleep and to reduce pain. It suppresses muscle spasms ‐ and so may prevent pain caused by MP ‐ without interfering with muscle function. The purpose of this review was to assess how effective cyclobenzaprine is at reducing pain and improving sleep in patients with MP. We searched extensively through scientific publications and found two trials, with a total of 79 participants. These tested cyclobenzaprine against another drug called clonazepam, and fake medication (placebo), or against injections of a local anesthetic called lidocaine. A total of 35 of the 79 participants in the two trials were given cyclobenzaprine. Cyclobenzaprine was slightly better than clonazepam and placebo at reducing jaw pain, but was no better at improving sleep quality. The results from the other trial were not scientifically reliable because of the small number of participants involved, but lidocaine injections seemed to reduce pain slightly better than cyclobenzaprine pills. Despite this result, it is likely that, because it is uncomfortable to receive any form of injection, people who suffer from MP will prefer to be treated with cyclobenzaprine pills. There were no life‐threatening adverse events associated with any of the medications studied. Further studies are needed to show whether cyclobenzaprine really works for treating MP, but at the moment doctors cannot say whether it is really useful.

Author(s)

Frederico MG Leite, Álvaro N Atallah, Regina El Dib, Eduardo Grossmann, Eduardo Januzzi, Regis B Andriolo, Edina MK da Silva

Reviewer's Conclusions

Authors' conclusions

Implications for practice

The limited available evidence, involving a total of 79 participants in two studies, suggests that cyclobenzaprine is similar to clonazepam and placebo for effectiveness and safety. Lidocaine infiltration showed mild superiority (not statistically significant) when compared to cyclobenzaprine, although it was associated with a higher ‐ but not significant ‐ number of adverse effects (pain and swelling). It is probable that the invasive characteristics of the infiltration procedure would encourage the use of cyclobenzaprine. In these circumstances, there is insufficient evidence either to support or refute the use of cyclobenzaprine for the treatment of MP.

Implications for research

The two included studies provided positive, but weak, evidence for using cyclobenzaprine to treat MP. Some methodologic flaws influenced validity and reproducibility of the conclusion. In addition, different diagnostic criteria were used in the included clinical studies. Therefore, more RCTs, especially multicenter trials with sufficient sample sizes, and more than one diagnostic criterion (in order to increase the external validity of their findings (applicability)) should be performed. Moreover, the diversity of ways of reporting estimate effects should be standardized by using clinically relevant and objective outcome variables, including quality of life. These are needed to establish cyclobenzaprine's true therapeutic effects, and, if that is shown, further studies would be required to establish the best dose and type of use of the drug.

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