Ask the Pharmacist: Are Skeletal Muscle Relaxants Useful in Management of Chronic Pain?

Concern about mounting opioid overdoses continued in 2020, and found the workers’ compensation and auto casualty industries in search of ways to mitigate opioid risks while still addressing the pain that comes with a workplace or auto injury. In the past, Mitchell Pharmacy Solutions has discussed options such as gabapentinoids, marijuana and non-pharmaceutical treatments, all of which have benefits and drawbacks. Another type of drug that many doctors are more frequently adding to treatment plans is skeletal muscle relaxants. As you consider your pharmacy program and the prescribing patterns for your patients, what should you know about this class of drugs? Are muscle relaxants a viable alternative to opioids?

Skeletal Muscle Relaxants: Definition and Uses

Skeletal muscle relaxants (SMRs) are a group of drugs used to treat muscle spasticity and spasm. Unlike other drug classes, the drugs in this category vary greatly and many have differing structural, pharmacologic and side effect profiles. This makes it difficult to make overarching recommendations on the entire category; however, certain key basics should drive prescribing decisions. SMRs are typically prescribed to treat pain associated with acute musculoskeletal conditions and for muscle spasms but are only recommended for a limited duration of use, as the safety and effectiveness of longer-term use is not supported. According to ODG Guidelines, skeletal muscle relaxants may be useful as a third-line option for treatment of chronic low back pain – the same tier as gabapentinoids and opioids. However, the guidelines state that SMRs are “not recommended for most patients with chronic low back pain due to lack of evidence” and that they “may be considered only ‘as-needed’ for acute flare-ups.” The guidelines additionally state that there is no evidence that skeletal muscle relaxants are more effective than NSAIDS, which are listed as a first-line option. The ODG Guidelines also recently updated the formulary to place Chlorzoxazone (Parafon Forte®), Metaxolone (Skelaxin®) and Tizanidine (Zanaflex®) in the "N" drug category. Learn more about the changes here. Skeletal muscle relaxants may also be dangerous when co-prescribed with opioids. The combination, according to the FDA, can cause slowed or difficult breathing or even death. A June 2020 study from the University of Florida, however, suggests that not all combinations are as dangerous, suggesting that short term use of a combination of SMRs and low-dose opioids is less likely to result in overdose. However, the study findings have not been reflected in any prescribing guidelines and SMRs are still not recommended for use with opioids.

Skeletal Muscle Relaxant Prescribing Patterns

Despite national guidelines and warnings against long-term use, prolonged skeletal muscle relaxant prescribing is increasing. A June 2020 study published in JAMA found that, between 2005 and 2016, continued SMR prescribing from U.S. physician visits tripled, from 8.5 million to 24.7 million. Additionally, “nearly 70 percent of patients prescribed muscles relaxants were simultaneously prescribed an opioid.” The study also found that older adults disproportionately received skeletal muscle relaxant prescriptions, despite being a high-risk population due to the potential for the drug to cause falls. This is particularly important for workers’ compensation, as a higher rate of severe injuries occur among older workers. A May 2019 study of workers’ compensation disability found that workers who received a short-term prescription for a skeletal muscle relaxant or NSAID were at lower risk for work disability compared to those who received a short-term opioid prescription. However, the study also found that an increase in days’ supply of any of these drugs was associated with work disability, supporting the ODG Guidelines recommendations to limit SMR prescriptions to short-term.

Guidance for Your Pharmacy Program

Skeletal muscle relaxants may be an effective second option in reducing pain and increasing mobility, when used in the short term. However, be sure to monitor your program for any long-term use, co-prescribing with opioids or use by older claimants. Work with your pharmacy benefit manager to look for concerning prescribing patterns or unsafe combinations and to put risk monitoring practices in place. For your adjusters, make sure they are aware of key skeletal muscle relaxants to look for as they monitor claims, and the drug-drug interactions such as with opioids that should raise concern. Some examples of SMRs are:

• Flexeril®- Cyclobenzaprine
• Soma®- Carisoprodol
• Robaxin®- Methocarbamol
• Parafon Forte®- Chlorzoxazone
• Zanaflex®- Tizanidine
• Lioresal®- Baclofen