OBJECTIVES: Aclidinium bromide is a long-acting muscarinic antagonistic used in maintenance treatment of chronic obstructive pulmonary disease (COPD). We evaluated the cost-effectiveness of aclidinium 400µg twice daily as an alternative to tiotropium 18µg once daily for this indication in the US by conducting a model-based health economic study.  METHODS: A cost-utility model was developed based on a time-in-state model structure. Patient characteristics in this model reflect those in aclidinium clinical studies: age >40 years; stable moderate-to-severe COPD; current or ex-smokers; post-salbutamol forced expiratory volume in 1 second (FEV1) ≥30% and <80% of predicted normal value and FEV1/forced vital capacity <70%. The model consists of 5 main health states indicating COPD severity and the level of utility, resource use, and costs. Treatment efficacy over 5-years time horizon was modeled using FEV1% predicted. Results of a network meta-analysis comparing aclidinium versus tiotropium were used to estimate disease progression during the first 24 weeks, while a common annual decline after 24 weeks was used, based on UPLIFT study data. Quality of life was assessed using utility scores in US patients from UPLIFT. Cost effectiveness was assessed as incremental cost per quality-adjusted life year (QALY) gained. The analysis was performed from a US third-party payer perspective.  RESULTS: Over 5 years, 4.52 life years were accumulated for both aclidinium and tiotropium, with QALYs of 3.50 and 3.49, respectively, and marginally lower numbers of exacerbations for aclidinium. Aclidinium showed lower mean total health care costs vs tiotropium (US$126,274 vs US$128,591, respectively). In all scenario analyses performed, aclidinium was associated with lower costs and marginally greater QALYs vs tiotropium. Limitations include use of network meta-analysis to estimate treatment effect and extrapolation of trial results.  CONCLUSIONS: These results indicate that aclidinium is potentially more cost-effective than tiotropium for the maintenance treatment of patients with moderate-to-severe COPD.