Description of anti-diabetic drug utilization pre- and post-formulary restriction of sitagliptin: findings from a national health plan

Abstract

Objective:

Multi-tiered formularies are commonly used for controlling costs of prescription medications. Focused on type 2 diabetes mellitus (T2DM), this database study assessed drug utilization before and after a formulary restriction (2nd–3rd tier), and compared demographic and clinical characteristics of patients affected vs not by the restriction.

Methods:

Formulary restriction of sitagliptin (SITA) occurred July 1, 2012. The ‘pre-period’ was defined from January 1–June 30, 2012, the ‘grace period’ from July 1–September 30, 2012, and the ‘post-period’ from October 1, 2012–March 31, 2013. Patients from the OptumInsight database were included if diagnosed with T2DM, ≥18 years, had continuous enrollment, and had ≥2 prescriptions of SITA in the pre-period. Those who died or were aged ≥65 years in the post-period were excluded. Patients were grouped into SITA continuer and discontinuer cohorts based on SITA use in the post-period. Descriptive analyses assessed baseline patient characteristics and anti-hyperglycemic drug utilization in the pre- and post-periods.

Results:

In total, 23,477 patients met inclusion criteria. In the post-period, 36.1% (n = 8480) of patients discontinued SITA. Among SITA discontinuers, 44.1% switched to a preferred DPP-4 inhibitor, 9.2% switched to glucagon-like peptides-1 (GLP-1) or insulin, and 2.4% switched to metformin or sulfonylurea. Of the SITA discontinuers, 21.6% dropped SITA without replacement and 8.4% discontinued all diabetes medications. In the post-period, a greater proportion of SITA discontinuers used GLP-1 (12.6% vs 5.8%) and insulin (29.1% vs 20.9%) than continuers, or had some change in anti-hyperglycemic treatment (67.5% vs 22.1%). Baseline demographic and clinical characteristics were similar between SITA continuers and discontinuers, indicating a lack of an association with SITA discontinuation.

Limitations:

This descriptive study used a non-controlled observational approach.

Conclusions:

Following formulary change, 1/3 of patients discontinued SITA and 30% of discontinuers received less intensive anti-hyperglycemic treatment in the post-restriction period. Meanwhile, 44% of discontinuers switched to a new preferred DPP-4 inhibitor.

Keywords: :

• Diabetes mellitus
• Drug utilization
• Cost sharing
• Pharmacy formulary
• DPP-4 inhibitors
• Managed care programs

Transparency

Declaration of funding

This study was funded by Merck & Company, Inc., Kenilworth, NJ, USA.

Declaration of financial/other relationships

X.H., Z.L., R.R.S., and S.R. are all full time employees of Merck & Co. Inc., Kenilworth, NJ, USA. X.H. designed the study, performed analyses, interpreted results, and provided substantive comments to the manuscript. Z.L. collected data, performed analyses, interpreted results, and provided substantive comments to the manuscript. R.R.S. and S.R. took part in study design, interpreted results, and provided substantive comments to the manuscript. CMRO Peer reviewers on this manuscript have received an honorarium from CMRO for their review work, but have no other relevant financial relationships to disclose.

Acknowledgments

The authors thank Michael Senderak of Merck for programming support and Becky Hanna of Asclepius Analytics LLC for writing assistance, which was funded by Merck & Co., Inc.