OBJECTIVES: Skeletal muscle relaxants (SMR) are commonly prescribed for relief of acute and painful musculoskeletal conditions, but secular trends and longitudinal patterns of their use are poorly described. We examined the annual prevalence and duration of SMR treatment among commercially insured US adults aged 18 to 64 years.

METHODS: In this retrospective cohort study, the Truven MarketScan Research Database was used to identify patients with musculoskeletal disorders and 11 years of continuous enrollment between 2005 and 2015. Using a repeated cross-sectional design and direct standardization method, we estimated the age-adjusted annual prevalence of SMR treatment. Using the Kaplan-Meier method, we derived treatment duration. Analyses were stratified by sex, age, and individual agents.

RESULTS: A total of 1,209,380 patients were included. The prevalence of SMR use increased slightly by 7% (prevalence rate ratio and 95% CI: 1.07 [1.05-1.09]) from 152.7 per 1,000 patients in 2005 to 163.2 in 2015. Cyclobenzaprine was the dominant agent accounting for more than half of the use. The considerable growth in the use of baclofen, tizanidine, and methocarbamol was in parallel with a decline in the use of metaxalone, orphenadrine and carisoprodol. The use of SMR was more prevalent among females, and age groups 35 to 44 and 45 to 54 years. Overall, the median duration of treatment was 15 days; 8.4%, 4.1%, and 2.1% of individuals used treatment for more than 90, 180, and 365 days, respectively. The duration increased with age and was slightly higher for females. Compared with cyclobenzaprine, patients initiated on baclofen, tizanidine, and carisoprodol experienced longer duration of treatment.

CONCLUSIONS: While the overall utilization of SMRs remained stable in recent years, the trend varies dramatically between individual agents. Despite limited evidence to support efficacy, prolonged use is common. Further study is needed to understand outcomes associated with long-term SMR use.