OBJECTIVES: Complicated intra-abdominal infections (IAIs) are a major cause of morbidity and mortality worldwide1. By acknowledging that IAIs are a public health issue in terms of the illness burden2, this study aimed to develop an economic model based on the perspectives of Brazilian health systems (Supplemental Health System [SHS] and Unified Health System [SUS]) in order to evaluate the cost-effectiveness of tigecycline/Pi-Tz and tigecycline/Im-Cl versus ertapenem/Im-Cl, ertapenem/Pi-Tz, Cef-Met/Im-Cl, and Cef-Met/Pi-Tz in first- and second-line treatment of adults with IAIs.  METHODS: With a decision-tree analysis all patients received first-line treatment at an inpatient unit and in case of treatment failure, they then received second-line treatment at an ICU. The treatment combinations considered for the evaluation of tigecycline cost-effectiveness in treating IAIs were tigecycline 100 mg/day, ceftriaxone/metronidazole 2G/1,5G/day and ertapenem 2G/day with imipenem/cilastatin or piperaciclin/tazobactam, considering a time horizon of 30 days. The measure for effectiveness was the percentage of clinical success retrieved from clinical trials in published literature and fitted for bacterial resistance by means of a conditional probability method; the costs and resources were retrieved from SUS3 and SHS4 databases, respectively. The model estimated the cost per patient and incremental cost-effectiveness ratios (ICER). RESULTS: Clinical success rate was of 76% on tigecycline groups versus 73% on ertapenem groups and 41% on ceftriaxone/metronidazole groups. The cost per patient in tigecycline groups both from SUS and SHS were lower (tigecycline/Pi-Tz: BRL 287,837.49/BRL 48,670.11 and tigecycline/Im-Cl: BRL 287,529.09/BRL 48,319.87, respectively) than in ertapenem groups (ertapenem/Im-Cl: BRL 293,523.73/BRL 51,985.92 and ertapenem/Pi-Tz: BRL 293,200.67/BRL 51,619.03, respectively) and in ceftriaxone/metronidazole groups (Cef-Met/Im-Cl: BRL 448,391.81/BRL 78,704.94 and Cef-Met/Pi-Tz: BRL 449,206.70/BRL 79,630.37, respectively) due to shorter length of stay and less complications. CONCLUSIONS: The cost-effectiveness analysis showed that tigecycline leads to cost-savings in the treatment of IAIs in Brazilian Health Systems and should be considered as a favorable treatment option for these infections.