Low back pain (LBP) is a painful condition that lies between the scapula and the fold of the inferior gluteus, with or without radiating to the knee and not caused by specific etiologies such as infection and malignancy, metastases, osteoporosis, fractures, neurological disorders, or conditions other pathological. Muscle relaxants can reduce acute non-specific low back pain symptoms and increase the side effects of sedation, nausea, headaches, and prone to abuse.

Relieve Low Back Pain using Muscle Relaxants
Image source: https://headtopics.com


Acute pain can generally be relieved without intervention, but sometimes the pain comes back and even persists in interfering with daily activities.

Muscle relaxants are a pharmacological therapy option to manage non-specific low back pain, both acute, subacute, and chronic. It is estimated that about 35% of patients who come to primary care physicians with low back pain complaints are prescribed muscle relaxants. However, this drug's use is still controversial, especially because its benefits are not yet clear, and the number of side effects it causes. Various studies have also provided different recommendations regarding the use of this drug.


Types of Muscle Relaxant Drugs

Muscle relaxants are drugs with various indications and different action mechanisms but have the same final effect, relaxing the muscles. There are two types of muscle relaxants, namely antispasmodics and anti-plasticity. Benzodiazepines are often categorized as muscle relaxants. However, benzodiazepines are gamma-aminobutyric acid (GABA) receptor agonists that cannot work in muscles because they do not have these GABA receptors. This misconception occurs because benzodiazepines cause relaxation due to their anxiolytic effects, which seem to have a muscle relaxant effect.

Antispasmodics are drugs that function to suppresses muscle spasms.  Another category is anti-plasticity drugs that function to reduce stiffness, such as those that occur in cerebral palsy, multiple sclerosis, and injuries to the spinal cord. Antispasmodic muscle relaxants, such as carisoprodol and cyclobenzaprine, are the most commonly prescribed medications for low back pain patients.


The Effectiveness of  Muscle Relaxants in Treating Low Back Pain

A meta-study consisting of 15 studies was conducted to determine the effectiveness and safety of using muscle relaxants to treat low back pain. Of these 15 studies, there were 5 good-quality randomized control trials (495 participants) that directly compared the effect of muscle relaxants with placebo in reducing pain scales in low back pain. The use of muscle relaxants significantly reduced acute low back pain in the short term with a mean difference in pain score reduction of -21.3 (95% CI -29 to -13.5; p <0.001). As for chronic low back pain, the use of muscle relaxants did not reduce pain significantly (mean difference -4.0 [95% CI -8.6 to 0.6]; p = 0.09). In that meta-analysis, 3 studies also compared muscle relaxants' ability to reduce disability in patients with low back pain. The results showed no significant clinical difference in reducing disability in the short term after muscle relaxants.

A recent meta-analysis of 22 studies also showed that muscle relaxant medication was superior to placebo in reducing short-term pain after 2-4 days of use (RR 1.25 [CI 1.12-1.41]; I2 = 0 %) and 5-7 days (RR 1.72 [CI 1.32-2.22]; I2 = 0%).


Combination of Muscle Relaxants with Other Analgesics

Pharmacological therapy for low back pain often uses a combination of NSAIDs, muscle relaxants, and opioids. An estimated 26% of patients receive a combination of NSAIDs and muscle relaxants, in addition to 16% of patients receiving a combination of NSAIDs, muscle relaxants, and opioids together.
A meta-analysis compared the effectiveness of using NSAIDs alone with combined NSAIDs and muscle relaxants to effectiveness for low back pain treatment. The addition of muscle relaxants did not provide additional anti-pain effects than NSAIDs alone to treat acute low back pain.


Side Effects of Muscle Relaxants

One of the components to consider using muscle relaxants is the risk of side effects. The study conducted showed that when compared to placebo, muscle relaxants increased the risk of side effects (nausea, drowsiness, and headache) with an RR of 1.50 (CI 1.14-1.98) and central nervous system side effects, especially sedation with RR 2.04 (CI 1.23-3.37; I2 = 50%). Muscle relaxants can also be addictive and prone to abuse. Until now, there have been no studies evaluating this condition.



Conclusion
Using muscle relaxants for acute low back pain can reduce pain in the short term. Its effect in managing chronic low back pain is not significantly proven. The use of muscle relaxants increases the side effects of sedation, nausea, headaches, and is prone to abuse. Therefore, this drug's administration must be done carefully and adapted to the specific patient's conditions and needs. The current evidence does not support the long-term administration of muscle relaxants for patients with low back pain.


References
1. A. Qaseem, T.J. Wilt, R.M. McLean, M.A. Forciea, Ann Intern Med, 2017, 166, 514-530.http://annals.org/aim/fullarticle/2603228/noninvasive-treatments-acute-subacute-chronic-low-back-pain-clinical-practice
2. B.W. Friedman, A.A. Dym, M. Davitt, L. Holden, C. Solorzano, D. Esses, et al., JAMA, 2015, 314(15), 1572-1580. https://jamanetwork.com/journals/jama/fullarticle/2463257
3. C.A. Shaheed, C.G. Maher, K.A. Williams, A.J. McLachlan, Eur J Pain, 2017, 21(2), 228-237. http://onlinelibrary.wiley.com/doi/10.1002/ejp.907/epdf
4. M.W. van Tulder, T. Touray, A.D. Furlan, S.Solway, L.M. Bouter, Cochrane Database of Systematic Reviews, 2003, http://onlinelibrary.wiley.com/doi/10.1002/14651858.CD004252/epdf/standard
5. P.D.Roelofs, R.A. Deyo, B.W. Koes, R.J. Scholten, M.W. vanTulder, Cochrane Database of Systematic Reviews, 2008, 1. http://onlinelibrary.wiley.com/doi/10.1002/14651858.CD000396.pub3
6. R. Chou, R. Deyo, J. Friedly, A. Skelly, M. Weimer, R. Fu, et al., Ann Intern Med, 2017, 166, 480-492. http://annals.org/aim/fullarticle/2603229/systemic-pharmacologic-therapies-low-back-pain-systematic-review-american-college