SGEM#366: Relax, Don’t Do It – Skeletal Muscle Relaxants for Low Back Pain

Date: May 13th, 2022 Reference: Abril et al. The Relative Efficacy of Seven Skeletal Muscle Relaxants. An Analysis of Data From Randomized Studies. J Emerg Med 2022 Guest Skeptic: Dr. Sergey Motov is an Emergency Physician in the Department of Emergency Medicine, Maimonides Medical Center in New York City. He is also one of the world’s leading researchers on pain management in the emergency department and specifically the use of ketamine. His twitter handle is @PainFreeED. Case: A 45-year-old man without a significant past medical history presents to your emergency department (ED) with two days of severe lower back pain after shoveling some dirt. The pain is 10/10 in intensity, gets worse with bending, turning, and prolonged walking. He denies numbness or paresthesia in both lower extremities, as well as bowel or bladder dysfunctions. A heating pad and acetaminophen has not helped with the pain. On examination, he is in moderate distress and has prominent tenderness to palpation at the bilateral paralumbar region and intact neurovascular examination. You diagnose him with a lumbar muscle strain and plan to prescribe him a non-steroidal anti-inflammatory (NSAID) while setting expectations. However, the patient wonders if you can give him something that can relax his back muscles and take his pain away. Background: Low back pain (LBP) is one of the most encountered ailments in clinical practice and is responsible for 2.6 million visits to U.S. EDs annually (1). Many patients with acute LBP experience substantial improvement in the first month, but up to one third report persistent back pain, and 1 in 5 report some limitations in activity. These persistent symptoms are associated with high costs, including those related to health care, and indirect costs from missed work or reduced productivity (2). Many pharmaceutical treatments besides opioids have been tried to address acute LBP pain with limited success (SGEM#87 and SGEM#173). These include: acetaminophen (Williams et al Lancet 2014), steroids (Balakrishnamoorthy et al Emerg Med J 2014) and benzodiazepines (Friedman et al Ann Emerg Med 2017). Nonsteroidal anti-inflammatory drugs (NSAIDs) are recommended as first-line medication therapy for patients with LBP despite a lack of evidence of efficacy (Machado et al Ann Rheum Dis 2017), There are several non-pharmaceutical treatments that have also been tried to treat LBP. They include: CBT and mindfulness (Cherkin et al JAMA 2016), chiropractic (Paige et al JAMA 2017), physical therapy (Paolucci et al J Pain Research 2018) and acupuncture (Colquhoun and Novella Anesthesia and Analgesia 2013). Unfortunately, none of these other treatment modalities has high-quality evidence supporting their use. Skeletal muscle relaxants (SMRs) are a frequently used in the ED and at discharge for acute back pain management and include methocarbamol, cyclobenzaprine, orphenadrine, carisoprodol, tizanidine, metaxalone, and baclofen. Estimates suggest up to 35% of patients with nonspecific low back pain are prescribed SMRs, with orphenadrine, and methocarbamol being used in more than 250,000 U.S. ED visits for low back pain annually (3-5). Despite their branding as muscle relaxants, the anti-spasmodic and analgesic effects of SMRs are predominantly due to unknown mechanism of action. Clinical Question: What is the efficacy of skeletal muscle relaxant administration in addition to an NSAID in treating acute low back pain? Reference: Abril et al. The Relative Efficacy of Seven Skeletal Muscle Relaxants. An Analysis of Data From Randomized Studies. J Emerg Med 2022 Population: Patients were considered for inclusion if they were 18– 69 years of age and presented to the ED primarily for management of acute LBP. This was defined as pain of two weeks’ duration or less originating between the lower border of the scapulae and the upper gluteal folds, and received a diagnosis consistent with nontraumatic,