The Effects of a Sitagliptin Formulary Restriction Program on Diabetes Medication Use

Health plans have responded to the many treatment options for type 2 diabetes mellitus by implementing formulary restriction policies, including step therapy, to control costs. Little is known about the impact of step therapy programs on antidiabetes medication use.

To assess the impact of a sitagliptin step therapy program on antidiabetes medication use among sitagliptin users.

Using pharmacy claims from the Symphony Health Solutions' Integrated Dataverse, we compared the use of sitagliptin and other antidiabetes medications by patients enrolled in a health plan (Plan A) that implemented a sitagliptin step therapy program on July 1, 2013, with the use by patients who were contemporaneously enrolled in 2 comparison plans-Plans B and C-without step therapy programs. Sitagliptin-a dipeptidyl peptidase (DPP)-4 inhibitor-was in tier 3 in Plans A and B and in tier 2 in Plan C during the study period. We assessed the use of antidiabetes medications during the pre-step therapy period (January-June 2013) and the post-step therapy period (October 2013-March 2014).

We identified 2995 patients enrolled in Plan A, 751 enrolled in Plan B, and 394 enrolled in Plan C who received sitagliptin during the pre-step therapy period. Patient characteristics and pre-step therapy sitagliptin use were similar across plans. During the post-step therapy period, more patients in Plan A (approximately 70%) discontinued sitagliptin than patients in Plan B (approximately 51%) and Plan C (approximately 25%). Approximately 30% of patients in Plan A switched to another DPP-4 inhibitor compared with approximately 15% and 2% of patients in Plans B and C, respectively. Seventeen percent of patients in Plan A discontinued sitagliptin without replacement but continued using other antidiabetes medications compared with approximately 13% and 8% of patients in Plans B and C, respectively. In all, 17% of patients in Plans A and B and 11% of patients in Plan C discontinued using all antidiabetes medications.

The step therapy program changed patients' use of sitagliptin, which was the target of the step therapy program, as well as of other antidiabetes medications. Most patients stopped sitagliptin treatment after the step therapy program started. Some patients discontinued sitagliptin treatment without replacement, but others discontinued using all antidiabetes medications.