Cyclobenzaprine may Help Neck Pain from Fibromyalgia

Flexeril for fibromyalgia

Could low-dose Flexeril (cyclobenzaprine) be approved for use in fibromyalgia?

A study published in The Journal of Rheumatology last month looked at the effects of cyclobenzaprine for fibromyalgia, a cause of neck pain in some patients. This drug, a muscle relaxant, is already widely used ‘off-label’ by fibromyalgia sufferers. Although this study is relatively small, with just eighteen patients treated, it does appear to show that cyclobenzaprine is safe and effective for the condition which causes fatigue, muscle tenderness and pain, and cognitive symptoms in patients.

Causes of Neck Pain in Fibromyalgia

Sleep disruptions are also a feature of fibromyalgia, and a possible contributing factor to the condition as patients often experience a lack of restorative sleep which affects muscle recovery. Lack of quality sleep also adversely affects pain tolerance, and fibromyalgia patients have been found to have higher levels of substance P in spinal canal fluid which also increases sensitivity to pain. The use of cyclobenzaprine at bedtime is used to help people with fibromyalgia relieve pain and tenderness, along with improving sleep. Other drugs for fibromyalgia are usually given for daytime use, with patients having no specific muscle relaxant prescribed for nighttime relief.


Current Cyclobenzaprine Products

TONIX Pharmaceuticals funded the study and are developing a lower dose of cyclobenzaprine for use in fibromyalgia cases. Around five million people in the US are thought to suffer from the condition, many using higher doses of the drug (5 or 10mgs) marketed by Amrix, Fexmid, and Flexeril. It appears that lower doses (up to 4mg per day) are effective for fibromyalgia however, thus reducing the risks of side-effects for patients compared to taking these other drugs ‘off-label’.

fibromyalgia neck pain

Tender points from fibromyalgia

Details of the Fibromyalgia Cyclobenzaprine Trial

The study carried out by University of Toronto researchers was a randomized, placebo-controlled trial involving an initial 37 patients, with 19 completing the study. The problem with placebo-controlled trials is that they do not compare a new treatment with an available treatment, rather they simply determine if a new drug is better than nothing. More trials are needed to really establish the usefulness of the drug and one scientist and doctor, Brian Walitt, an assistant professor of medicine at Georgetown University, has already commented on the study (for WebMD) saying that, overall, the new drug dose, if approved, ”is not going to change things substantially for people with fibromyalgia”.

Improvements in Fibro Pain with Cyclobenzaprine


Results from the trial do indicate improvements in the patients treated with cyclobenzaprine over the placebo, with a 26% reduction in pain compared to no pain reduction in the placebo group. The placebo group did experience a 3.2% improvement in tenderness however, but the improvement in fibromyalgia tenderness in the treatment group was significant at 30.1%. Sleep time was also seen to improve from 5.7hrs to 6.4hrs in the treatment group, with subsequent decreases in fatigue, although this was not significant. Patients also reported slightly less depression after the 8week study, with a 22% decline in depression scores (on the Hospital Anxiety and Depression scale) compared to a 10.4% increase in the placebo group. Looking at the actual scores however reveals a change from 6.3 to 4.9 for treated patients, and a change from 6.7 to 7.4 in the placebo group, with all scores on a 21 point scale. Although these differences may be significant for individual patients they are unlikely to be a primary selling point of the drug. Some news reports have said that depression improvements in the treatment group were 38% more than in the placebo group, demonstrating the effectiveness of statistics to make headlines.

Cyclobenzaprine Side-Effects

Side-effects of cyclobenzaprine were observed during the study with headaches being the most commonly reported adverse event. Some 39% (seven patients) taking cyclobenzaprine experienced headaches, compared to three patients in the placebo group (17%). Other effects in treatment vs placebo groups included dizziness (3 patients vs 1 patient), nausea (2 vs 5), pruritis (2 vs 1), and somnolence (4 vs 2).

Cyclobenzaprine Approval for Fibromyalgia

All of the patients in the study were white, with a mean age of 43yrs and all but one were women. Half of the patients in both placebo and treatment groups had had fibromyalgia for more than 6years and had received prior therapy for the condition (with the exception of one patient). The researchers’ spokesman Seth Lederman speculated that the drug could be brought to market in 2015 but gave no indication of its possible cost. Current generic cyclobenzaprine products, which are higher dose than those likely to be prescribed for treating fibromyalgia, cost between $70 and $90 for a box of thirty 10mg pills, with the branded Flexeril products costing over $100 dollars for the same dose and quantity. Patients with neck pain and tenderness caused by fibromyalgia, particularly where sleep is being disrupted, may wish to ask their doctor about cyclobenzaprine as a bedtime muscle relaxant.


Reference

Moldofsky, H., Harris, H.W., Archambault, T., Kwong, T., Lederman, S., Randomized Placebo-controlled Study: Physiology in Patients with Fibromyalgia Syndrome: A Double-blind
Effects of Bedtime Very Low Dose Cyclobenzaprine on Symptoms and Sleep, The Journal of Rheumatology, DOI: 10.3899/jrheum.11019

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