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Abstract
Objective:
Chronic pain is prevalent in patients with major depressive disorder (MDD). This study compared adherence and persistence rates among MDD patients with comorbid chronic pain-related diseases (CPD, including fibromyalgia, diabetes with neurological manifestations, osteoarthritis, low back pain, and headache) for three antidepressants: duloxetine, venlafaxine XR, and escitalopram.
Research design and methods:
A retrospective analysis was conducted of 15,523 adult MDD patients with CPD in the MarketScan Commercial Claims and Encounters Database who started on one of the study medications between 07/01/06 and 06/30/07. Patients were followed-up for 6 months. Adherence was reported using a medication possession ratio ≥0.8. Persistence was measured using persistence rates (proportions of patients who continuously refilled prescriptions during 6 months) and duration of therapy (number of days patients remained on the study medication before a prescription gap over 30 days). Multivariate logistic regression on adherence and persistence rates and linear regression on duration of therapy adjusting for patient and prescription characteristics were conducted.
Results:
Patients on duloxetine had a higher adherence rate (46.03%) than those on venlafaxine XR (42.94%; p = 0.0033) or escitalopram (37.27%; p < 0.0001). Patients on duloxetine also had a higher persistence rate and longer duration of therapy (43.66%, 117.82 days) than did patients treated with venlafaxine XR (40.38%; p = 0.0017; 114.24 days; p = 0.009) or escitalopram (33.86%; p < 0.0001; 105.73 days; p < 0.0001). These differences were still significant after adjusting for patient and prescription characteristics (p < 0.05). Sensitivity analyses found similar patterns using an allowable gap for refill of 15 days.
Conclusions:
Among commercially insured MDD patients with CPD, duloxetine-treated patients had higher adherence and persistence rates than did patients treated with venlafaxine XR or escitalopram during 6 months after medication initiation. Future studies should examine the clinical and economic implications of these differences.
Limitations:
This study has limitations such as possible selection bias using secondary database analysis.
Transparency
Declaration of funding
This study was supported by Eli Lilly and Company. Lilly provided comments on the research design and study findings, but the authors jointly made final decisions on every aspect of the manuscript. All authors participated in the literature review, study design, results interpretation, and manuscript revisions. J.W. carried out data analysis and produced the first draft of the manuscript.
Declaration of financial/other relationships
X.L. was a full-time employee of Eli Lilly and Company and minor shareholder at the time of this study. C.D.M. receives consulting income, honoraria, and/or grant support from GlaxoSmithKline, Lilly, Novartis, Pfizer, and Sanofi-Aventis. CMRO peer reviewers on this manuscript have disclosed that they have no relevant financial relationships.
Acknowledgments
The authors would like to thank David L. Armbruster, PhD, for his editorial assistance. Dr. Armbruster was not paid by the authors.
This study was presented as a poster at the Drug Information Association Conference on Evidence-Based Medicine and Health Technology Assessment respectively: Moving from Separate Appraisal to Synergistic Communications on March 23, 2010, in Washington, DC and at the American Psychiatric Association Annual Meeting on May 24, 2010, in New Orleans, LA, USA.
Notes
* Lexapro is a registered trademark of Forest Laboratories, Inc., New York, NY, USA.
† Cymbalta is a registered trademark of Eli Lilly and Company, Indianapolis, IN, USA.
‡ Effexor XR is a registered trademark of Wyeth Pharmaceuticals Inc., Madison, NJ, USA.