Impact of Schedule IV controlled substance classification on carisoprodol utilization in the United States: An interrupted time series analysis

Abstract Background In January 2012, the Drug Enforcement Agency (DEA) classified carisoprodol as a Schedule IV controlled substance at the US federal level. We aimed to examine the effect of this policy on the use of carisoprodol in a commercially-insured population. Methods This interrupted time series study included individuals with musculoskeletal disorders in the IBM MarketScan Commercial Database between December 2009 and February 2014. We used comparative segmented linear regression to assess changes in the proportions of patients who filled/newly filled carisoprodol each month. Results A total of 13.3 million patients were included. 29 states with no scheduling prior to the DEA classification had lower baseline prevalence of carisoprodol use compared to 17 states that had scheduled carisoprodol individually before 2010 (11.0 vs. 21.1 patients with fills per 1,000 patients). The federal scheduling was associated with an immediate decline (–1.12 per 1,000 patients, p  Conclusions Schedule IV controlled substance classification at the federal level was associated with a moderate reduction in the dispensing of carisoprodol regardless of whether scheduling was already present at the state level.