Comparison of Medication Adherence and Healthcare Costs between Duloxetine and Pregabalin Initiators among Patients with Fibromyalgia

Abstract

To examine and compare medication adherence and direct healthcare costs between duloxetine and pregabalin initiators among patients with fibromyalgia. A retrospective analysis of commercially insured fibromyalgia patients aged 18 to 64 was conducted among those who initiated duloxetine or pregabalin between January 1, 2006 and December 31, 2006. The first initiation date was defined as the index date. All patients included had continuous enrollment in the 12-month pre- and post-index periods. Each individual was classified in the duloxetine or pregabalin cohort based on the initiating agent. The pregabalin cohort was constructed via propensity scoring controlling for differences in demographics, pre-index clinical and economic characteristics, and pre-index treatment patterns. Medication adherence (ie, medication possession ratio [MPR] and proportion of patients with MPR≥80%) and healthcare costs over the 12 months post-index period were examined between cohorts. The study cohorts included 3,711 duloxetine and 4,111 pregabalin patients with the mean age of 51 years. The common comorbidities included neuropathic pain other than diabetic peripheral neuropathic pain, low back pain, cardiovascular disease, headache, and osteoarthritis. Over 80% of the duloxetine or pregabalin initiators used opioids. Controlling for demographics, pre-index clinical and economic characteristics, and prior medication history, duloxetine patients had significantly higher MPR (0.7 vs. 0.5, P<0.05), higher proportion of patients with MPR≥80% (46.5% vs. 26.4%, P<0.05), but significantly lower total healthcare costs ($19,378 vs. $27,045, P<0.05) over the 12 months post-index period than pregabalin patients. Fibromyalgia patients on duloxetine had significantly higher medication adherence, but significantly lower direct healthcare costs than those on pregabalin.