Utilization Patterns of Skeletal Muscle Relaxants Among Commercially Insured Adults in the United States from 2006 to 2018

Abstract

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.

Skeletal muscle relaxant drug–drug–drug interactions and unintentional traumatic injury: Screening to detect three‐way drug interaction signals

“…One exception includes investigations of the combination of SMRs, opioids and benzodiazepines, which has been associated with an elevated risk of overdose and ED visits, compared with use of two of these drugs alone. 3,28 Aligned with these findings, we found that use of clonazepam was associated with a 1.7-fold increased rate of unintentional traumatic injury among patients receiving tizanidine + oxycodone. Interactions among tizanidine, oxycodone and clonazepam are biologically plausible given additive or synergistic pharmacodynamic effects (e.g., CNS depression) from all three drugs, and the potential pharmacokinetic interplay between clonazepam and oxycodone.…”

“…US ambulatory care visits resulting in new or continued therapy with an SMR doubled from 15.5 million in 2005 to 30.7 million in 2016 2 . In 2018, approximately 1 in 15 commercially insured Americans was treated with an SMR 3 . This increasing and widespread SMR use is concerning, given their uncertain efficacy for off‐label indications and high‐risk safety profiles 1 .…”

“…2 In 2018, approximately 1 in 15 commercially insured Americans was treated with an SMR. 3 This increasing and widespread SMR use is concerning, given their uncertain efficacy for off-label indications and high-risk safety profiles. 1 Most SMRs have central nervous system (CNS) sedation effects causing dizziness, ataxia and confusion, thereby potentially precipitating accidental falls, unsafe operation of motor vehicles and traumatic injuries.…”

“…6 SMRs are frequently used with other medications. 2,3,5 In 2016, two-thirds of US ambulatory care visits that continued SMR therapy documented opioid use. 2 In a cohort of older US veterans newly prescribed SMRs, 72% received six or more medications.…”

Demonstration of relative bioavailability of newly developed and innovator drug metaxalone 800 mg in healthy subjects under fed condition

“…Time for highest drug attentiveness (Tmax) deferred by 1 h and terminal half-life diminished 6.6 h in served condition equated to abstained. [ 3 4 ]…”