Background: Carisoprodol is a muscle relaxant indicated as adjunctive therapy in acute, painful musculoskeletal conditions. Case reports of drug-seeking behavior and utilization of carisoprodol in combination with opioids have suggested abuse potential.
Objectives: We undertook a retrospective review of claims data to identify and characterize potential indicators of abuse in long-term users of carisoprodol and to determine any continued use of the drug by former long-term users following prior authorization implementation.
Methods: The Idaho Medicaid pharmacy and medical claims database was queried from January 1 to December 31, 2005, to identify long-term users of muscle relaxants. Use of concomitant opioids and coded diagnoses relating to past drug abuse were analyzed and compared between patients who used carisoprodol and patients who used other muscle relaxants. Data from 11 of 30 surveys mailed to pharmacies filling prescriptions for long-term users of carisoprodol were also collected to determine the frequency of self-pay-continued use after Medicaid coverage of the drug was discontinued.
Results: Long-term users of carisoprodol (n = 340) and other skeletal muscle relaxants (SMRs) (n = 453) were identified from among 130,000 individuals in the Idaho Medicaid pharmacy and medical claims database in calendar year 2005. Patients in both groups were similar in terms of mean age (~47 years) and sex (71.5% female). Patients using carisoprodol used concomitant opioids more frequently (81.5% vs 59.8%; P < 0.01), more commonly had past diagnoses indicating other drug abuse (34.1% vs 21.4%; P < 0.01), and in 80% of reported cases, continued to pay out of pocket for carisoprodol when third-party coverage was discontinued. Taken together, these findings are consistent with published case reports suggesting the abuse potential of carisoprodol.
Conclusions: The results from this review suggest that, compared with long-term users of other SMRs, carisoprodol patients utilized concomitant opioids more frequently and concomitant NSAIDs less frequently, more commonly had past diagnoses indicating other drug dependence or abuse, and continued to pay out of pocket for carisoprodol when third-party coverage was discontinued. While none of these issues alone may be direct indicators of abuse, collectively they suggest that patients who used carisoprodol long term displayed abuse potential characteristics more frequently than long-term users of other agents.