The aim of this study is to investigate the influence of excipients on physical and aerosolization stability of spray dried Ciprofloxacin dry powder inhaler formulations. The model drug, Ciprofloxacin hydrochloride, was co-spray dried with excipients such as disaccharides (sucrose, lactose, trehalose), mannitol and L-leucine. The spray dried samples were stored at two different relative humidity (RH) conditions of: (1) 20% and (2) 55% RH at 20°C. Ciprofloxacin co-spray dried with disaccharides...