OBJECTIVES: Antibiotic-resistant Gram-negative bacteria prevalence in Italy is one of the highest in Europe, causing the need of new therapeutic options effective on resistant strains. The aim of this study is to estimate the budget impact following the introduction of Zerbaxa in the treatment of complicated intra-abdominal infections (cIAIs) and complicated urinary tract infections (cUTIs) both for the Italian National Health Service (NHS) and at a regional level. METHODS: A budget impact model was developed over a 3-year time horizon using local epidemiological data. We used real data of market consumption (IMS data, year 2015-2016) to estimate the relative share of products used in the Italian setting (flouroquinolones, penicillins, cephalosporins, carbapenems) for the treatment of cUTIs and CIAIs. Market penetration of Zerbaxa was based on manufacturer’s assumptions. Data were validated by three experts which received questionnaires. Unit costs were taken from Italian standard sources. Univariate sensitivity analyses were conducted on key model parameters. RESULTS: A total of 11,009 cIAIs infections and 16,325 cUTIs infections were considered as model population at the first year, with an assumed 16.8% annual growth rate. The introduction of Zerbaxa over the next 3 years, assuming a market share of 0.76%, 3.26% and 12.16% respectively for the first, second and third year for cIAIs and 1.10%, 4.71% and 17.57% for cUTIs would lead to a total of approximately €12.1 million cost increase to the Italian NHS (4.9 million for cIAIs and 7.2 million for cUTIs). At a regional level, cost increase ranged from approximately €25k for Valle d’Aosta region to €2 million for Lombardia region. CONCLUSIONS: This analysis suggests that the use of Zerbaxa for the treatment of cIAIs and cUTIs would lead to an increase in cost to the Italian NHS lower than 5% over three years of total expenses for treating these infections.