Duloxetine compliance and its association with healthcare costs among patients with diabetic peripheral neuropathic pain.

OBJECTIVE: Duloxetine is approved to treat diabetic peripheral neuropathic pain (DPNP) in the US. The study objective was to examine the predictors of duloxetine compliance, and its association with healthcare costs among DPNP patients.
METHODS: The study used administrative claims databases to identify non-depressed DPNP patients with a duloxetine prescription dispensed between October 1, 2004 and December 31, 2006. Two cohorts of patients were constructed based on compliance to duloxetine therapy over 1-year follow-up with high compliance defined as a medication possession ratio (MPR) > or =0.80. All-cause, diabetes-, and DPNP-related healthcare costs during 1-year follow-up were estimated. Logistic regressions were performed to examine how average daily dose (ADD) of duloxetine and other factors may influence compliance. Multivariate regressions were estimated to examine the association between compliance and healthcare costs.
RESULTS: The study included 1,380 commercially insured (mean age 55 years) and 974 patients with employer-sponsored Medicare supplemental insurance (mean age 75 years). In both populations, patients with an ADD >30 mg were more likely to be compliant with the therapy compared with those with an ADD of < or =30 mg (odds ratio ranged 1.79-3.38, all p<0.05). Controlling for differences in demographics, clinical and economic characteristics, commercially insured low duloxetine compliance patients had greater all-cause ($5,334, p<0.05) and diabetes-related healthcare costs ($3,414, p<0.05) than high-compliance patients, with the biggest difference from inpatient costs (all-cause: $7,508; diabetes-related: $3,785, all p<0.05). Similar trends were found in the Medicare supplemental insured population; however, differences in all-cause healthcare costs were not significant.
CONCLUSIONS: DPNP patients with a higher ADD of duloxetine over a 1-year follow-up period were more compliant with the therapy. Duloxetine patients with high compliance were also associated with lower healthcare costs. Due to the use of a retrospective cohort design on administrative claims database, limitations of this analysis include a lack of formal diagnostic testing of patients, and inability to infer causality or measure factors such as DPNP severity that are not captured in such database.