Utilization patterns of skeletal muscle relaxants among commercially insured adults in the United States from 2006 to 2018.

Objective To examine the prevalence and duration of skeletal muscle relaxant (SMR) treatment among commercially insured adults. Methods We used the MarketScan Research Database to identify a cohort of adults 18 to 64 years who had ≥ two-year continuous enrollment between 2005 and 2018. We estimated the prevalence of SMR treatment using a repeated cross-sectional design and derived treatment duration using the Kaplan-Meier method. Analyses were stratified by age group, sex, geographic region, individual SMR agent, and musculoskeletal disorder. Results 48.7 million individuals were included. Treatment prevalence ranged from 61.5 to 68.3 per 1000. About one-third of users did not have a preceding musculoskeletal disorder diagnosis. Cyclobenzaprine was the dominant agent accounting for >50% of prescriptions. The considerable growth in the use of baclofen, tizanidine, and methocarbamol paralleled with a decline in carisoprodol and metaxalone use. The prevalence was highest in the South while lowest in the Northeast. The median treatment duration was 14 days with 4.0%, 1.9%, and 1.0% of individuals using SMRs for more than 90, 180, and 365 days. Compared with cyclobenzaprine, patients initiating baclofen, tizanidine, and carisoprodol had longer treatment duration. Conclusions SMRs are widely used in the United States. Their use slightly increased in recent years but trends varied among individual agents, patient groups, and geographic regions. Despite limited evidence to support efficacy, a sizable number of U.S. adults used SMRs for long-term and off-label conditions. Further study is needed to understand determinants of treatment as well as outcomes associated with such use.