4. Future perspectives

Pulmonary administration is a promising route for drug delivery to prevent and treat diseases, especially for delivering the drugs for lung diseases and some small molecule drugs with low absorption rate when in oral dosage form, also suitable for some traditional Chinese medicines and peptide or protein drugs. PDDS can effectively deliver the therapeutic drugs to the target sites, and improve the drug bioavailability and therapeutic efficacy. Inhalation is a noninvasive method for pulmonary administration, and the inhaled drugs can directly enter the blood circulation through the absorption of the alveolar epithelium. Pulmonary administration can enhance the drug absorption rate, reduce systemic side-effects, and improve the compliance of long-term medication. By transforming the drugs into dry powder inhalation formulations, drug degradation can be avoided. The therapeutic effect of the PDDS is mainly influenced by the physicochemical properties of the DDS, the dosage forms, and the administration devices, and also some other factors. The increase of the amount of drug delivered into the lung and the promotion of drug absorption rate are the key factors to improve the therapeutic efficiency of pulmonary administration. The application of sustained or controlled release preparations is an important method to prolong drug action time, enhance drug bioavailability, and improve patient compliance. In recent years, many controlled release preparations or active targeting preparations for pulmonary drug delivery have been constructed by drug-loaded microparticles, liposomes, and NPs. These multifunctional drug carriers have gained increasing popularity in pulmonary administration. It is really inspiring for us to see that some of the PDDS have already been applied to treat patients in clinic and become commercially available

commodities with promising prospects. And in the coming years, great progress will be made in PDDS research by the development of drug delivery devices and pharmaceutical preparation technology.

Acknowledgements

Applications of Chitosan in Pulmonary Drug Delivery DOI: http://dx.doi.org/10.5772/intechopen.87932

Conflict of interest

Author details

175

Xiuwen Guan1,2 and Weifen Zhang1,2\*

Medicine, Weifang, Shandong, PR China

provided the original work is properly cited.

\*Address all correspondence to: zhangwf@wfmc.edu.cn

The authors are thankful to the generous financial support from the National Natural Science Foundation of China (81774125) and National Key Technology R&D Program of the Ministry of Science and Technology (2013GA740103).

1 College of Pharmacy, Weifang Medical University, Weifang, Shandong, PR China

2 Shandong Engineering Research Center for Smart Materials and Regenerative

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

The authors declare no conflicts of interest in this work.

The PDDS constructed with biomaterials has been a hot research direction in medicine and pharmacy fields for decades. Among these biomaterials, CS, which is the only natural cationic polysaccharide, has been recognized as one of the most versatile and promising functional biomaterials. Moreover, CS is also one of the most abundant regeneration resources, second only to the cellulose. After decades of research, CS has been recognized as a nontoxic, biocompatible (especially with respiratory cells) and biodegradable polymer. Moreover, CS can accommodate both hydrophilic and hydrophobic drugs due to its amphiphilic properties [5]. The excellent performances of CS as a building component of DDS have been confirmed by many studies, and it has been identified as a novel drug delivery carrier with broad application prospects, especially for sustained and controlled drug release. Due to the unique features, CS can assist the drugs accomplishing local and systemic delivery, realizing high mucoadhesion, and efficient drug absorption in target tissues, which is especially applicative for PDDS. However, CS is insoluble in aqueous solutions at neutral and alkaline pH, and it only can be dissolved in aqueous acidic media (pH < 5). This frustrating issue has badly limited CS's application range, and there is an urgent need for developing convenient and practical modification strategies to improve its solubility. Up to now, CS has been approved as safe by US-FDA and EU for dietary use and wound dressing applications [85]. And additionally, CS has only been approved by the European Pharmacopeia as a pharmaceutical excipient for oral preparations. The safety issues of CS and its derivatives in pulmonary delivery and other administration routes have not been fully understood and still remain to be further evaluated. Therefore, the safety issue is a noteworthy research gap remained to be filled in the future work, for figuring out the potential adverse effects of CS and its derivatives in humans. At the same time, appropriate engineering of designing and modifying CS and its derivatives is highly demanded to optimize the performance of the CS-based drug carriers, for meeting the special requirements of in vivo pulmonary drug delivery. We hope that in the near future, more advanced synthesis and modification methods will be developed. And in the meanwhile, the physicochemical property, toxicity, biodistribution, biocompatibility, and biodegradability of CS and its derivatives should also be thoroughly investigated in detail.
