OBJECTIVES: Lennox-Gastaut Syndrome (LGS) is an epileptic encephalopathy characterized by intractable seizures of many types. LGS has its onset in early childhood, and often persists into adulthood. It is estimated that the prevalence of LGS among children and adults with epilepsy is 6.5% and 1.5%, respectively. This budget impact model was developed to help US payers make informed decisions regarding the addition of rufinamide for the management of LGS.  To analyze overall budget impact of changing rufinamide from tier 3 to tier 2 status for a large U.S. payer. METHODS: The budget impact model was constructed based upon the indicated population for rufinamide, which is children 4 years and older and adults (18+) requiring adjunctive treatment of seizures associated with LGS. The model follows patients over three years and estimates the direct health care costs associated with LGS treatment before and after the introduction of rufinamide. The three main categories of data inputs informing the model include: plan population inputs, treated prevalence inputs, and treatment and cost inputs. The base case model results are based on data derived from published literature, publicly available data sources, or assumptions. The results are presented as follows: total costs over 3 years, cost per member per year (PMPY), cost per treated member per year (PTMPY), cost per member per month (PMPM), and cost per treated member per month (PTMPM). RESULTS: Assuming a one  million member  plan and a discount rate of 3% shifting rufinamide from tier 3 to tier 2 resulted in $1,001 in additional total costs over 3 years. This translates to a change in a PTMPY of $1.00 and a PTMPM of $0.13. PMPY and PMPM were not notably affected. CONCLUSIONS: Based on this analysis changing rufinamide from tier 3 to tier 2 does not exhibit a significant cost increase.