OBJECTIVES: To determine the cost effectiveness of colistimethate sodium for the treatment of infections caused by multidrug-resistant (MDR)  METHODS: We compare key outcomes related to survival, infection averted and costs for infections caused by MDR. A lifetime Markov model was used to estimate the expected outcomes and costs for patients treated with colistimethate sodium vs non- colistimethate sodium group. Colistimethate sodium at a dosage of 5mg/kg/day was given intravenously in two divided doses. Primary outcomes were the clinical response and 30-day mortality; secondary outcomes were microbiological response and adverse events. The cost-effective analysis was conducted from the Mexican Healthcare perspective. Costs were derived from the literature, future costs and effects were discounted at 5% per recommendations for analyses in  Mexico. All costs are presented in 2013 US dollars. Multiple 1-way and Probabilistic sensitivity analyses were performed. RESULTS: In the colistimethate sodium group, 80.8% had a favorable clinical response, the overall mortality of the patients in the colistimethate sodium group was 46.2% and that in the non- colistimethate sodium group was 80%.  Nephrotoxicity was found in 30.8% in the colistimethate sodium group. The model projects an accumulated discounted cost to the Mexican healthcare system per patient receiving the Colistimethate sodium regimen of $8,525 compared to $7,384 for non- colistimethate sodium regimen. The base-case analysis presented incremental cost-effectiveness ratios for colistimethate sodium vs non- colistimethate sodium grup of $ 2,213 per LYG. These values are in accordance with the recommendations of the Commission on Macroeconomics and Health, WHO, suggesting that health technologies with ICERs below the per capita GDP are considered very cost-effective. Results were robust to various assumptions tested in the sensitivity analysis. CONCLUSIONS: This study suggest that in the Mexican setting, use of non- colistimethate sodium for treatment of infections caused by MDR is likely to be cost effective.