Patterns of health care utilization related to initiation of amitriptyline, duloxetine, gabapentin, or pregabalin in fibromyalgia

Abstract

Introduction: Several pharmacologic treatments are available for fibromyalgia, but little is known about the comparative effectiveness of these treatments on health care utilization. Methods: Using US commercial insurance claims data (covering 2007 to 2009), we conducted a cohort study to examine the comparative effectiveness of amitriptyline, duloxetine, gabapentin, and pregabalin on health care utilization in patients with fibromyalgia. We measured patients' medication adherence using the proportion of days covered (PDC) and estimated multivariable rate ratios (RRs) for outpatient visits, prescriptions, hospitalization, and emergency department (ED) visits in propensity score (PS)-matched cohorts. Results: Cohorts of 8,269 amitriptyline, 9,941 duloxetine, and 18,613 gabapentin initiators were compared with their PS-matched pregabalin initiators. During the baseline 180-day period, patients had, on average, seven to nine physician visits, including six to eight specialist visits, and received eight prescription drugs. The mean PDC up to 180 days varied from 38.6% to 67.7%. The number of outpatient visits, prescriptions, and hospitalizations decreased slightly after initiating one of the study drugs, but the number of ED visits increased after treatment initiation. Compared to pregabalin, duloxetine was associated with decreased outpatient visits (RR, 0.94. 95% confidence interval (CI), 0.88 to 1.00), prescriptions (RR, 0.94. 95% CI, 0.90 to 0.98), hospitalizations (RR, 0.75. 95% CI, 0.68 to 0.83), and ED visits (RR, 0.85. 95% CI, 0.79 to 0.91). Little difference in health care utilization rates was noted among amitriptyline and gabapentin initiators compared to those who were started on pregabalin. Conclusions: Fibromyalgia patients had high health care utilization before and after initiation of amitriptyline, duloxetine, gabapentin, or pregabalin. Medication adherence was suboptimal. Overall, fibromyalgia treatment had little impact on reducing health care utilization, but duloxetine initiators had less health care utilization than those started on pregabalin.