Abstract
Protein and peptide drugs have tremendous therapeutic potential, and their usage in the treatment of various severe diseases has revolutionized the fields of pharmaceuticals and biotechnology. For successful therapeutic effects, several efforts have been made to deliver protein/peptide drugs through various routes of administration. Parenteral and nonparenteral drug deliveries are regarded as significant routes of drug absorption. However, there is a need to improve nonparenteral drug delivery systems (DDSs) through subsequent routes, including buccal, pulmonary, oral, ocular, transdermal, and nasal routes to increase drug absorption effectively. The study evaluated various DDS routes proposed for the distribution of proteins and peptides in terms of both parenteral and nonparenteral delivery systems. For this purpose, numerous research articles were searched from the year 2000 to 2021 using search engines such as PubMed, Google Scholar, Medline, ISI Web of Knowledge, and Bioline International while applying different keywords such as “protein and peptide drugs,” “drug delivery systems,” “parenteral and nonparenteral routes of drug delivery,” and “physicochemical barriers.” The invasive/parenteral routes have several limitations associated with drug delivery, such as poor patient compliance and the pain and discomfort associated with these routes inconvenience in treating the pediatric population. The oral route is one of the most convenient routes of noninvasive or nonparenteral drug administration; here, no pain and discomfort arise, thus helping in maintaining higher patient compliance or acceptance. The other routes of administration of proteins and peptides through buccal, intranasal, pulmonary, transdermal, rectal, and ocular routes have also been showing successful results. The success of the therapeutics is strongly influenced by the differential delivery of the targeted antigen, the choice of targeting protein or peptide, and the drug-release characteristics of the linker used. Furthermore, there should be an improvement in nonparenteral DDSs so that the drugs might be administered appropriately.