Prescription dispensing patterns before and after a workers' compensation claim: an historical cohort study of workers with low back pain injuries in British Columbia

OBJECTIVE: Compare prescription dispensing before and after a work-related low back injury. METHODS: Descriptive analyses were used to describe opioid, nonsteroidal anti-inflammatory drug (NSAID), and skeletal muscle relaxant (SMR) dispensing 1 year pre- and post-injury among 97,124 workers in British Columbia with new workers' compensation low back claims from 1998 to 2009. RESULTS: Before injury, 19.7%, 21.2%, and 6.3% were dispensed opioids, NSAIDs, and SMRs, respectively, increasing to 39.0%, 50.2%, and 28.4% after. Median time to first post-injury prescription was less than a week. Dispensing was stable pre-injury, followed by a sharp increase within 8 weeks post-injury. Dispensing dropped thereafter, but remained elevated nearly a year post-injury, an increase attributable to less than 2% of claimants. CONCLUSION: These drug classes are commonly dispensed, particularly shortly after injury and dispensing is of short duration for most, though a small subgroup receives prolonged courses