The Effect of Skeletal Muscle Relaxants in Lower Back Pain

Clinical Question

In patients with acute nonradicular lower back pain for less than 2 weeks, would nonsteroidal antiinflammatory drugs (NSAIDs) and skeletal muscle relaxants, when compared to NSAIDs alone, help to improve functionality and reduce back pain?

Bottom Line

In patients with acute nonradicular lower back pain for less than two weeks, nonsteroidal antiinflammatory drugs (NSAIDs) plus skeletal muscle relaxants have not shown to improve functionality and reduce back pain when compared to NSAIDs alone.

Major Points

Nonsteroidal antiinflammatory drugs (NSAIDs) have been used extensively for decades in treatment of acute lower back pain. Skeletal muscle relaxants have never yielded a large amount of evidence for the improvement of musculoskeletal injuries. Although not much research has supported the use of them, skeletal muscle relaxants are commonly used to treat back pain in conjunction with NSAIDs. Up until 2017, it was never truly tested to see whether NSAIDs alone or NSAIDs in addition to skeletal muscle relaxants would yield the most positive outcomes for patients. In 2017, researchers at an emergency department evaluated the effect of adding muscle relaxants to NSAIDs using a randomized, double blinded placebo-controlled trial. There were 320 participants considered eligible for the study, scoring a score greater than 5 on the Roland-Morris Disability Questionnaire. All patients were given ibuprofen and were randomly given one of four options to take at home: baclofen, metaxalone, tizanidine, or a placebo. After seven days, improvement on the Roland-Morris Disability Questionnaire was determined, being the primary outcome. Secondary outcomes included pain intensity and need for medication. It was found that the most improvement on the Roland-Morris Disability Questionnaire was made in the placebo group. Patients who were placed into the placebo control group had the lowest percentage of moderate to severe lower back pain when compared to the other arms. Through this data, it was found that adding the skeletal muscle relaxants did not yield anymore improvements than NSAIDs alone. The study showed that although skeletal muscle relaxants are often prescribed by doctors for non radicular lower back pain, they show no improvement in the patients functionality or improvement in back pain. Limitations to the study include that the study was performed in an urban setting and may not be generalized to other areas. Additionally, pain was rated on a subjective scale, since different patients can have different pain tolerances and a short follow up period of 7 days may not have been adequate enough to see the full effect of skeletal muscle relaxants. There are no guidelines for this study. Although there is a fair amount of criticisms, the study was conducted very well and yielded results that can be implemented into practice since there was not a large difference in the outcomes between patients given a placebo and patients given a skeletal muscle relaxant.

Guidelines

As of April 19th, 2020, no guidelines have been published addressing this topic.

Design

Trial Type: Randomized, double-blinded placebo-controlled trial. N: 320 patients. Each of the four arms contained 80 patients. Setting: Outpatient after an acute emergency department visit for back pain. Enrollment: Patients were enrolled from 2017-2018. Mean follow-up: One week after visit to the emergency department. Analysis: Intention to treat. Primary outcome: The primary outcome for this trial was an improvement in RMDQ (Roland Morris Disability Questionnaire) from baseline after seven days post emergency department visit while reducing the risk of adverse drug events.

Population

Inclusion Criteria

Present to the emergency department for lower back pain not including flank pain. Musculoskeletal etiology of lower back. Patients were not admitted to the ED and were treated outpatient. Patients were aged 18-64. Patients had nonradicular pain (pain below the gluteal folds). Patient’s pain extended no longer than 2 weeks and was not traumatic pain. Patients did not have acute lower back pain attacks more than once a month. Functionally impairing back pain with a baseline RMDQ score of above 5.

Exclusion Criteria

Patients not available for follow-up Pregnant or breast-feeding patients Patients with chronic pain syndrome using an analgesic medication daily Patients with a contraindication to NSAIDs. Patients with a contraindication to muscle relaxants

Baseline Characteristics

Ibuprofen + Placebo Mean age: 39 Sex → 44 Men; 36 Women Work Status → 6 Unemployed; 1 Student; 8 <30h/wk; 65 ≥30h/wk Roland-Morris Disability Questionnaire Score at ED visit → 5 with <10; 35 with 10-19; 40 with 20-24 Previous episodes of low back pain → 15 Never; 52 A Few; 13 At Least Once/y (+) Depression Screening: 3

No significant differences in other groups.

Interventions

Patients were given 1 out of 4 medications regimens, each included ibuprofen 600mg every 8 hours as needed, as well as a placebo orally, baclofen 10mg, metaxalone 400 mg, or tizanidine 2mg orally. Each arm was instructed to take either one or two capsules by mouth three times a day as needed. The ibuprofen was not masked in this clinical trial. The baclofen, metaxalone, tizanidine, and placebo were masked and called investigational medication. The tablets were placed into capsules packed with lactose. The patients were advised that if one capsule of muscle relaxant gave sufficient relief, there was no need to take another capsule. Although if the patient did not see sufficient relief within 60 minutes of taking one capsule, they may take a second capsule. Each patient was provided with a 10 minute educational intervention on back pain. Follow up after one week of emergency department visit

Outcomes

Comparisons are intensive therapy vs. standard therapy.

Primary Outcomes

Improvements reported with a mean score of 10.8 (95% CI 9.8 to 11.8) one week after ED discharge

Secondary Outcomes

166 out of 312 (53% [CI 48%-59%]) patients that reported moderate to severe pain at 48 hours 101 out of 304 (33%[CI 28%-39%]) patients reported moderate or severe pain at one week 285 out of 312 (91% [88%-94%]) patients reported use of medications for lower back pain at 48 hours 192 out of 304 (63% [CI 58%-68%]) patients reported use of medications for lower back pain at 1 week 33 out of 304 (11% [CI 8%-15%]) patients reported use of additional health care resources the week after ED discharge

Adverse Events

Adverse events were not serious and were only experienced in 24 out of 283 patients (11% [CI 8%-15%]) Ibuprofen and Placebo: 5 participants reported events such as headache, nausea, diarrhea, and urinary complaints. Ibuprofen and Baclofen: 7 participants reported events such as dizziness, drowsiness, nausea, headache, diplopia, and muscle spasm. Ibuprofen and Metaxalone: 6 participants reported events such as constipation, drowsiness, dry mouth, abdominal pain, dizziness, and vaginal bleeding. Ibuprofen and Tizanidine: 6 participants reported events such as anxiety, dry mouth, dizziness, and drowsiness.

Criticisms

The study was performed in an urban setting and may not be generalized to other areas. The patients were required to self-titrate meaning some patients who needed more medication were allowed to take a second pill. Pain was rated on a subjective scale, since different patients can have different pain tolerances. Short follow up period of 7 days may not have been adequate enough to see full effect of skeletal muscle relaxants. Adherence to medications was not ensured.

Funding

Nation Institutes of Health/National Center for Advancing Translational Science Einstein-Montefiore CTSA grant

Further Reading

Friedman BW, Irizarry E, Solorzano C, et al. “A Randomized, Placebo-Controlled Trial of Ibuprofen Plus Metaxalone, Tizanidine, or Baclofen for Acute Low Back Pain”. Annals of Emergency Medicine. 2019; 74(4):512-520.