OBJECTIVES: Humana implemented a step therapy (ST) policy on pregabalin for Medicare and commercial plans effective January 2009, and lifted the policy for Medicare plans only in April 2013. This study examined the impact of the (ST) on pregabalin utilization and therapeutic alternatives, as well as medical expenditures for diabetic peripheral neuropathy (DPN), post herpetic neuralgia (PHN), and fibromyalgia (FM). METHODS: An interrupted time series design examined monthly pharmacy and medical claims during January 2007 – April 2014.  Segmented regression analyses allowed for two change points: January 2009 and April 2013 accounting for policy implementation and lift, respectively. Results were reported as the average number of claims per 100,000 members per month (P100KMPM) for time trend and level change following ST changes. RESULTS: The ST implementation resulted in a statistically significant decrease in pregabalin use by Medicare members, while its lift resulted in a marginally significant increase (level change after ST: -198.2 P100KMPM [P<.001]; level change after lift: 50.5 P100KMPM [P=.072]) in pregabalin use by Medicare members. There was no change over time after the ST implementation or lift. As a comparator, the level change for commercial members was -107.3 P100KMPM (P<.001) but remained flat following the lift (P=.730).  Utilization of anticonvulsants in Medicare, which contains the ST prerequisite therapy gabapentin, saw a consistent increase following the implementation of the pregabalin ST (trend change after ST: 11.2 P100KMPM [P=0.032]; level change after lift: 289.5 P100KMPM [P<0.001]; and trend change after lift: -22.1 P100KMPM [P=.002]). Medical expenditures for DPN, PHN, and FM among the Medicare population increased throughout the study period, but did not appear to be impacted by the pregabalin ST (P=.062, P=.361, P=.778 for DPN, FM and PHN respectively for level change following implementation). CONCLUSIONS: Humana’s ST edit policy has shifted members away from pregabalin but without significant impact on disease-related medical costs.