Utilization of duloxetine and celecoxib in osteoarthritis patients

To describe utilization patterns of duloxetine and celecoxib and subsequent opioid use among patients with osteoarthritis.

Pharmacy and medical claims from SDI Health were analyzed for adult osteoarthritis patients (ICD-9-CM: 715.xx) who initiated duloxetine or celecoxib between 11/30/2010 and 4/30/2011. Initiation was defined as no pill coverage in the prior 90 days. Included patients had continuous enrollment for 6 months before and after the initiation and did not use opioid for 90 days before initiation. Propensity score matching was used to select patients with similar demographic and clinical characteristics for duloxetine and celecoxib cohorts. Compliance to index medication was assessed via medication possession ratio (MPR), proportion of days covered (PDC), and proportion discontinued (no access for 60 days). Initiating dose and opioid use after the index date was assessed. A Cox proportional hazard model was estimated to compare time to first opioid use.

A total of 1360 patients initiated duloxetine and 1408 patients initiated celecoxib. After matching, 784 patients were selected for the duloxetine (mean age: 66, female: 78%) and celecoxib (mean age: 66; female: 76%) cohorts, respectively. Of the duloxetine cohort 92.5% started on ≤60 mg/day, the recommended dose, and 72.8% of the celecoxib cohort started on ≤200 mg/day. The duloxetine cohort had higher MPR and PDC and a lower proportion of discontinuation than the celecoxib cohort (MPR: 0.81 vs. 0.70; PDC: 0.51 vs. 0.35; discontinuation: 57% vs. 78%; all p < 0.001). A lower proportion of the duloxetine cohort used opioids after the index date (48.6% vs. 68.5%, p < 0.001), and they started on opioids later than the celecoxib cohort (25th percentile: 69.5 vs. 32 days; median: >183 days vs. 117 days, p < 0.001). After controlling for baseline characteristics, the duloxetine cohort initiated opioids later than the celecoxib cohort (hazard ratio: 0.66, 95% confidence interval: 0.58-0.76).

Osteoarthritis patients initiating duloxetine had better compliance and a lower likelihood of opioid utilization than those initiating celecoxib. Study limitations included lack of information on reasons for medication initiation and discontinuation, severity of disease symptoms, and use of over-the-counter medications.