Duloxetine Use in Chronic Low Back Pain

Abstract

Little is known about the real-world treatment patterns and costs of patients with chronic low back pain (CLBP) who are treated with duloxetine compared with those receiving other non-surgical treatments. Our objective was to compare the real-world treatment patterns and costs between patients with CLBP who initiated duloxetine and matched controls who initiated another non-surgical treatment. The study sample was selected from a US privately insured claims database (2004-8). Selected patients were aged 18-64 years, and had a low back pain (LBP) diagnosis (per Healthcare Effectiveness Data and Information Set [HEDIS] specifications) with a subsequent CLBP-qualifying diagnosis recorded ≥90 days after the initial LBP diagnosis. Duloxetine-treated patients had ≥1 duloxetine prescription within 6 months after CLBP diagnosis, no prior duloxetine claim, and continuous eligibility ≥12 months before first LBP diagnosis and ≥6 months after index duloxetine prescription (study period). Because duloxetine patients had higher rates of co-morbidities, 553 duloxetine-treated patients were matched to 553 control patients who initiated another non-surgical LBP treatment based on propensity score and time from first LBP diagnosis to treatment initiation. A subset (n = 103 each) of matched employees with disability data was also analysed to assess work loss. Main outcomes measures included study period treatment rates and direct (medical and drug) costs from a third-party payer perspective and employee indirect (work-loss) costs. McNemar tests were used to compare LBP treatment rates. Bias-corrected bootstrapping t-tests were used to compare costs. After matching, the two groups had balanced baseline characteristics including demographics, LBP diagnostic categories, co-morbidity profiles, resource use, treatment patterns and mean direct costs. During the 6-month study period, matched duloxetine-treated patients had significantly lower rates of other pharmacological therapy (e.g. 56.2% vs 64.9% narcotic opioids, p = 0.0024; 34.9% vs 49.5% NSAIDs, p < 0.0001) and non-invasive therapy (28.8% vs 38.5% chiropractic therapy, p = 0.0007; 25.5% vs 35.4% physical therapy, p = 0.0004; 17.5% vs 28.4% exercise therapy, p < 0.0001) than controls. Duloxetine-treated patients versus controls had similar back surgery rates (2.2% vs 3.8%; p = 0.1127) and similar direct costs ($US7658 vs $US7439; p = 0.8119). Among CLBP employees, duloxetine-treated employees versus controls had lower rates of other non-surgical therapy, similar back surgery rates (0.0% vs 3.9%; p = 0.1250), lower total direct and indirect costs ($US5227 vs $US7299; p = 0.0418), and similar indirect costs ($US1806 vs $US2664; p = 0.0528). Duloxetine treatment in CLBP patients/employees versus other non-surgical treatment was associated with reduced rates of non-surgical therapies and similar back surgery rates, without increased costs.