Effect of pill burden on dosing preferences, willingness to pay, and likely adherence among patients with type 2 diabetes

A Brett Hauber,¹ Steven Han,^2,3 Jui-Chen Yang,¹ Ira Gantz,² Kaan Tunceli,² Juan Marcos Gonzalez,¹ Kimberly Brodovicz,² Charles M Alexander,² Michael Davies,² Kristy Iglay,² Qiaoyi Zhang,² Larry Radican<sup>2

1</sup>Health Preference Assessment, Research Triangle Institute (RTI) Health Solutions, Research Triangle Park, NC, USA; ²Merck Sharp and Dohme Corporation, Whitehouse Station, NJ, USA; ³Temple University, Philadelphia, PA, USA

Purpose: To quantify willingness-to-pay (WTP) for reducing pill burden and dosing frequency among patients with type 2 diabetes mellitus (T2DM), and to examine the effect of dosing frequency and pill burden on likely medication adherence.
Patients and methods: Participants were US adults with T2DM on oral antihyperglycemic therapy. Each patient completed an online discrete-choice experiment (DCE) with eight choice questions, each including a pair of hypothetical medication profiles. Each profile was defined by reduction in average glucose (AG), daily dosing, chance of mild-to-moderate stomach problems, frequency of hypoglycemia, weight change, incremental risk of congestive heart failure (CHF), and cost. Patients were asked to rate their likely adherence to the profiles presented in each question. Choice questions were based on a predetermined experimental design. Choice data were analyzed using random-parameters logit. Likely treatment adherence was analyzed using a Heckman two-stage model.
Results: Of the 1,114 patients who completed the survey, 90 had lower dosing burden (<5 pills/day taken once/day or as needed) for all medications, and 1,024 had higher dosing burden (≥5 pills/day or more than once/day). Reduction in AG was valued most highly by patients. Hypoglycemia, chance of mild-to-moderate stomach problems, weight change, incremental risk of CHF, and daily dosing were less valued. Patients with higher current dosing burden had lower WTP for more convenient dosing schedules than patients with lower current dosing burden. Changes in dosing and cost impacted likely adherence. The magnitude of the impact of dosing on likely adherence was higher for patients with lower current dosing burden than for patients with higher current dosing burden.
Conclusion: Patients with T2DM were willing to pay for improvements in efficacy, side effects, and dosing. Patients' WTP for more convenient dosing depended on current dosing burden, as did the effect of these attributes on likely adherence.

Keywords: discrete-choice experiment, conjoint analysis, willingness to pay, adherence, type 2 diabetes mellitus, oral antihyperglycemic therapy