Manufacturer-sponsored drug coupon use and drug-switching behavior among patients with type 2 diabetes.

Background: Patients often use manufacturer-sponsored coupons to reduce their out-of-pocket spending. However, little is known whether coupon use is associated with medication-switching behaviors.

Objective: To examine if using a manufacturer-sponsored coupon to initiate a medication is associated with patterns of medication-switching behaviors among patients with type 2 diabetes.

Methods: Using IQVIA's retail pharmacy claims data from October 2017 to September 2019, we analyzed commercially insured patients with type 2 diabetes who had newly started taking the following noninsulin diabetes drugs: generic metformin (nearly no coupon use), Sodium-glucose Cotransporter-2 (SGLT2) Inhibitors (SGLT2, high coupon use), and dipeptidyl peptidase IV inhibitors (DPP-IV inhibitors, moderate coupon use). We assessed if drug-switching behaviors, defined as no switching, switching to a same-class drug, or switching to a drug in a different class, differed among patients who did and did not use coupons to initiate treatments. We performed multinomial logistic regression to estimate the probability of each switching type associated with patients' initial coupon use.

Results: Among 9,781 patients in our sample, 83.7% of them initiated treatments with metformin, 8.2% with SGLT2, and 8.1% with DPP-IV inhibitors. The overall switching rate was the lowest for generic metformin (40%) than brand-name drugs (56%-57%). Among the brand-name drug users, patients who used a coupon to initiate these drugs were less likely to switch to any drug compared with patients without coupon use (SGLT2 = -18% [95% CI = -24% to -13%]; DPP-IV inhibitors = -9% [-16% to -2%]). These patients were also less likely to switch to drugs in other competing classes (SGLT2 = -16% [95% CI = -22% to -10%]; DPP-IV inhibitors = -9% [-16% to -2%]).

Conclusions: Patients who started their treatment with generic metformin had the lowest rate of drug switching. Using coupons to initiate brand-name drugs in classes with prevalent coupons was associated with reduced medication switching to other class drugs.