Historical cohort analysis of treatment patterns for patients with type 2 diabetes initiating metformin monotherapy

Abstract

Objective:

To describe treatment regimen changes of patients with type 2 diabetes mellitus (T2DM) initiating metformin monotherapy, and assess factors associated with those changes 12 months post-initiation.

Methods:

Retrospective cohort analysis of medical, pharmacy and laboratory claims of 17,527 Medicare Advantage (MAPD) Humana members aged 18–89, who had ≥1 medical claim with primary diagnosis or ≥2 medical claims with secondary diagnosis of T2DM (ICD-9-CM code 250.x0 or 250.x2) who filled an initial prescription for metformin (GPI code 2725) between 1 January 2008 and 30 September 2011. The main outcome measure was change in metformin monotherapy during the 12 months following initiation. Factors associated with treatment changes during follow-up were examined using Cox proportional hazards regression models.

Results:

Fifty-nine percent of patients (mean age 69.6 years) remained on metformin monotherapy with no changes. Discontinuation was the most common treatment change (33%), followed by addition (5%), and switching (2%) to other antidiabetics. Of patients who discontinued treatment (median time to discontinuation = 90 days), 61% did not reinitiate any diabetic treatment during the follow-up period. Among patients who added or switched to other antidiabetics, sulfonylureas were the most common addition or replacement agent. Predictors of discontinuation were being female, Black or Hispanic, low-income subsidy eligible, having higher initial out-of-pocket metformin costs, or a diagnosis of depression. Discontinuation was less likely during follow-up if patients had higher pre-index pill burdens or records of a pre-index A1C screening test. A higher risk of discontinuation was observed for patients with low baseline A1C. One study limitation was that exact discontinuation dates could not be determined using claims.

Conclusions:

The findings suggest that gender, race, ethnicity, depression, and low income status were contributory factors to metformin discontinuation. More intensive monitoring and treatment adjustments may be warranted for patients newly initiated on metformin. This could ultimately improve morbidity, mortality, and costs associated with poor glycemic control.

Keywords: :

• Adults
• Age 65 plus
• Metformin therapeutic use
• Type two diabetes mellitus

Transparency

Declaration of funding

This study was sponsored by Novo Nordisk Inc.

Author contributions: All authors participated in the design of the study, interpretation of the results, and in the progress and critical revisions of the manuscript. All authors read and approved the final draft.

Declaration of financial/other relationships

L.H.-F., Y.X. and C.M. have disclosed that they are employees of Comprehensive Health Insights, a Humana company, which received funding from Novo Nordisk to conduct this study. Y.M. has disclosed that he is a Humana employee and stockholder. J.B. has disclosed that she/he was an employee of Humana at the time that this manuscript was prepared and declares no conflict of interest. J.L. has disclosed that she/he was an employee of Novo Nordisk at the time this manuscript was prepared. E.K. and J.B. have disclosed that they are employees of Novo Nordisk Inc.

CMRO peer reviewers on this manuscript have no relevant financial or other relationships to disclose.

Acknowledgments

The authors thank Mary Costantino PhD of Comprehensive Health Insights, and Tulay Cushman PhD of Novo Nordisk Inc. for medical writing assistance and critical reviews through the development of this manuscript.

Previous presentation: Data presented at International Society of Pharmacoeconomics and Outcomes Research, Annual International Meeting, Montreal, CA, June 2014.