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Pulmonary pharmaceutical formulations are targeted for the treatment of respiratory diseases. However, their application is limited
due to physiological characteristics of the lungs such as branching structure, mucociliary and macrophages, as well as certain properties of the
drugs like particle size and solubility. Nano-formulations can ameliorate particle sizes and improve drug solubility to enhance bioavailability in
the lungs. The nano-formulations for lungs reviewed in this article can be classified into nanocarriers, no-carrier-added nanosuspensions and
polymer-drug conjugates. Compared with conventional inhalation preparations, these novel pulmonary pharmaceutical formulations have their
own advantages, such as increasing drug solubility for the better absorption and less inflammatory reaction caused by the aggregation of
insoluble drugs; prolonging pulmonary retention time and reducing drug clearance; improving the patient compliance by avoiding multiple
repeated administrations. This review will provide the reader with some background information for pulmonary drug delivery and give an
overview of the existing literature about nano-formulations for pulmonary application to explore nano-strategies for improving bioavailability of
pulmonary pharmaceutical formulations.