OBJECTIVES: Severe myoclonic epilepsy in infancy (SMEI, Dravet Syndrome) is a severe type of pharmacoresistant epilepsy, characterized by repeated and prolonged generalized seizures. Patients with SMEI show important delays in psychomotor and cognitive development that often progress in eventual mental retardation. Stiripentol (STP) has been approved in Canada for use in conjunction with valproate (VPA) + clobazam (CLB) as adjunctive therapy in patients with SMEI whose seizures are not adequately controlled with VPA+CLB alone. The objective of this study was to assess, from a Canadian perspective, the economic impact of STP+VPA+CLB compared with VPA+CLB in the treatment of SMEI. METHODS: The cost-effectiveness of STP+VPA+CLB compared to VPA+CLB in the treatment of SMEI was assessed over a 5-year horizon using a Markov model. The model comprises four health states: not adequately controlled (NAC), not seizure free (NSF), seizure free (SF) and death. The length of each Markov cycle is 1 year for the whole study period. Patients could stay in the NAC state, move to the NSF or SF state, or die, according to the respective efficacy of each treatment. Utility values associated with each health state were used to estimate the number of QALYs associated with each treatment. Analyses were conducted from both a Canadian Ministry of Health (MoH) and a societal perspective. RESULTS: Compared with VPA+CLB, STP+VPA+CLB was associated with incremental cost-effectiveness ratios of CAD$50,122/QALY from a MoH perspective and was dominant from a societal perspective. Results of the probabilistic sensitivity analysis indicated that the ICUR remained below CAD$100,000 in 98.4% and in 100% of the simulations from a MoH and a societal perspective respectively. CONCLUSIONS: This economic evaluation demonstrates that STP+VPA+CLB is a cost-effective strategy as adjunctive therapy in patients with SMEI whose seizures are not adequately controlled with VPA+CLB alone.