There are now 12 classes of antihyperglycemic medications available for patients with type 2 diabetes mellitus (DM). With an estimated 30 million patients in the United States living with DM1 and increasing complexity and financial burden of DM care, the relative distribution of expenditures across DM therapeutic classes needs to be reexamined. We evaluated trends in aggregate use and expenditures for all DM therapies among US Medicare Part D beneficiaries from 2012 to 2017.

Methods

We analyzed 2012 to 2017 Medicare Part D Prescription Drug Event data. All classes of antihyperglycemic therapies, defined by the American Diabetes Association, were identified.2 Bromocriptine and colesevelam were excluded given overlapping indications and infrequent use. Total spending (both Medicare Part D and beneficiary payments) were adjusted for inflation and presented in 2017 US dollars. Annual spending, number of claims, and spending per claim were extracted. Descriptive computations were performed using STATA statistical software (version 14.1, StataCorp). Because these deidentified data were publicly available and did not contain detailed patient characteristics, institutional review board approval was waived by the institutional review board of Partners HealthCare.

Results

In 2017, Medicare Part D spent $22 billion on all DM therapies (144% increase from 2012). Medicare spent $94 billion on DM therapies from 2012 to 2017, including $60 billion on insulin ($55 billion on analog, $5 billion on human) (Figure 1A). Medicare filled 36% more analog insulins prescriptions but 17% fewer human insulin prescriptions over this timeframe (Figure 2A). Since 2015, spending increases for analog insulin have slowed, driven by plateauing in per-claim spending for long-acting insulins (Figure 1B).

Noninsulin therapies accounted for $3.7 billion in 2012 and $8.7 billion in 2017 (135% increase) (Figure 1B). The costliest noninsulin therapies were dipeptidyl peptidase-4 inhibitors (DPP-4i), which increased from $1.5 billion to $3.9 billion (156% increase). The next 2 costliest noninsulin therapies were the glucagon-like peptide-1 receptor agonists (GLP-1RA) and the sodium-glucose cotransporter-2 inhibitors (SGLT2i). Total spending on GLP-1RA increased from $374 million on 753 855 prescriptions in 2012 to $2.6 billion on 2.7 million prescriptions in 2017. In 2014, Medicare Part D spent $165 million on 381 093 SGLT2i prescriptions, which increased to $1.2 billion on 2 million SGLT2i prescriptions in 2017.

Between 2012 and 2017, the most commonly prescribed antihyperglycemic therapy was metformin (163 million prescriptions at $17/prescription). Similarly, Medicare spent $14 per prescription on 95 million prescriptions on sulfonylureas. Amylin analogues were the least commonly prescribed antihyperglycemic therapy, but had the highest per-claim cost. Driven by decreasing per-claim cost, overall spending for thiazolidinediones decreased by 93% (from $956 million to $65 million). Spending (not included in the above estimates) from 2012 to 2017 on combination products was $5 billion on 15.6 million claims.

Discussion

Spending for DM-related therapies is rising rapidly among Medicare beneficiaries in the US. Although insulins, primarily analog insulins, remain the primary drivers of cost,3 overall insulin expenditure growth appears to be slowing. In contrast, spending on newer antihyperglycemic therapies is increasing, driven by not only greater uptake, but also longitudinal increases in per-claim costs of DPP-4i, GLP-1RA, and SGLT2i. The DPP-4i class remains the most costly noninsulin therapy despite lack of established cardiovascular benefits and only modest glycemic efficacy.

Increased aggregate spending has not been accompanied by apparent improvements in population-level glycemic control.4 However, it is uncertain whether greater use of SGLT2i and GLP-1RA, classes with proven cardiovascular benefits, may still advance value by averting downstream complications and health care expenditures.

Our data do not account for patient-level characteristics (including cardiovascular risk) and thus do not inform appropriateness of spending changes. We also could not differentiate expenditures related to types of DM, distinguish new vs existing prescriptions, or account for manufacturer rebates or discounts.

Conclusions

As DM prevalence in the United States is projected to remain high, costs of DM therapeutics may pose barriers to affordability and adherence. Further work is needed to capture health system costs of DM care to potentially redistribute current expenditures to high-value care practices.

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Corresponding Author: Muthiah Vaduganathan, MD, MPH, Brigham and Women’s Hospital Heart & Vascular Center, Harvard Medical School, 75 Francis St, Boston, MA 02115 (mvaduganathan@bwh.harvard.edu).

Accepted for Publication: July 24, 2019.

Published Online: September 30, 2019. doi:10.1001/jamainternmed.2019.3884

Author Contributions: Drs Sumarsono and Vaduganathan had full access to all of the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis.

Study concept and design: Sumarsono, Butler, Pandey, Vaduganathan.

Acquisition, analysis, or interpretation of data: Sumarsono, Everett, McGuire, Fonarow, Butler, Vaduganathan.

Drafting of the manuscript: Sumarsono, Butler, Vaduganathan.

Critical revision of the manuscript for important intellectual content: All authors.

Study supervision: Butler, Pandey, Vaduganathan.

Conflict of Interest Disclosures: Dr Everett reports receiving grant support and/or consulting for Amarin, Amgen, Merck, Novartis, and Roche Diagnostics, the National Heart, Lung, and Blood Institute, the National Institute of Diabetes and Digestive and Kidney Diseases, and the US Food and Drug Administration. Dr McGuire reports honoraria for trial leadership from Astra Zeneca, Sanofi Aventis, Janssen, Boehringer Ingelheim, Merck & Co, Pfizer, Novo Nordisk, Lexicon, Eisai, GlaxoSmithKline, Esperion, Lilly US; and honoraria for consulting for Astra Zeneca, Sanofi Aventis, Lilly US, Astra Zeneca, Boehringer Ingelheim, Merck & Co, Pfizer, Novo Nordisk, Metavant, and Applied Therapeutics. Dr Fonarow reports significant consulting for Novartis, and modest consulting for Abbott, Amgen, Bayer, Janssen, and Medtronic. Dr Butler has received research support from the National Institutes of Health, the Patient-Centered Outcomes Research Institute, and the European Union; and serves as a consultant for Amgen, Array, AstraZeneca, Bayer, Boehringer Ingelheim, Bristol Myers Squib, CVRx, G3 Pharmaceutical, Innolife, Janssen, Luitpold, Medtronic, Merck, Novartis, Relypsa, StealthPeptide, SC Pharma, Vifor, and ZS Pharma. Dr Pandey is supported by the Texas Health Resources Clinical Scholars Program. Dr Vaduganathan is supported by the KL2/Catalyst Medical Research Investigator Training award from Harvard Catalyst (NIH/NCATS Award UL 1TR002541), serves on advisory boards for Amgen, AstraZeneca, Bayer AG, Baxter Healthcare, and Boehringer Ingelheim, and participates on clinical end point committees for studies sponsored by Novartis and the NIH. No other conflicts are reported.