Biopharmaceutics pulmonary

Parenteral administration is not perceived as a problem in the context of drugs which are administered infrequently, or as a once-off dose to a patient. However, in the case of products administered frequently/daily (e.g. insulin to diabetics), non-parenteral delivery routes would be preferred. Such routes would be more convenient, less invasive, less painful and generally would achieve better patient compliance. Alternative potential delivery routes include oral, nasal, transmucosal, transdermal or pulmonary routes. Although such routes have proven possible in the context of many drugs, routine administration of biopharmaceuticals by such means has proven to be technically challenging. Obstacles encountered include their high molecular mass, their susceptibility to enzymatic inactivation and their potential to aggregate. 

Pulmonary delivery currently represents the most promising alternative to parenteral delivery systems for biopharmaceuticals. Delivery via the pulmonary route moved from concept to reality in 2006 with the approval of Exubera, an inhalable insulin product (Chapter 11). Although the lung is not particularly permeable to solutes of low molecular mass (e.g. sucrose or urea), macromolecules can be absorbed into the blood via the lungs surprisingly well. In fact, pulmonary... 

P. Colombo, D. Cocconi, P. Santi, R. Bettini, G. Massimo, P. L. Catellani, C. Terzano, Biopharmaceutical Aspects of Nasal and Pulmonary Drug Delivery , in Pharmacokinetic Optimization in Drug Research Biological, Physicochemical and Computational Strategies , Eds. B. Testa, H. van de Waterbeemd, G. Folkers, R. Guy, Verlag Helvetica Chimica Acta, Zurich, 2001, p. 173- 188. 

Although no biopharmaceutical product delivered to the bloodstream via the pulmonary route has been approved to date, several companies continue to pursue active research and development programmes in the area. Amongst the leading product candidates is Exubera , an inhalable dry powder insulin formulation currently being evaluated by Pfizer and Aventis Pharma in Phase III clinical studies. The inhaled insulin is actually more rapidly absorbed than if administered subcutaneously and appears to achieve equivalent glycaemic control. While promising, final approval or otherwise of this product also depends upon additional safety studies which are currently under way. 

Due to the lack of activity after oral administration for most peptides and proteins, administration by injection or infusion - that is, by intravenous (IV), subcutaneous (SC), or intramuscular (IM) administration - is frequently the preferred route of delivery for these drug products. In addition, other non-oral administration pathways have been utilized, including nasal, buccal, rectal, vaginal, transder-mal, ocular, or pulmonary drug delivery. Some of these delivery pathways will be discussed in the following sections in the order of the increasing biopharmaceutic challenges to obtain adequate systemic exposure. 

Biopharmaceutical Challenges Pulmonary Delivery of Proteins and Peptides... 

With the advent of new biotechnological techniques endogenous compounds like insulin, buserelin or octreotide have become available at affordable prices. All of these substances still have to undergo needle application. Until today the development of alternative delivery systems for the nasal, buccal, peroral, rectal and pulmonary routes for the administration of those class III drugs according to the biopharmaceutics classification system (BCS) (Amidon et al. 1995) could not keep pace with this development of endogenous compounds or is not economic enough for the health care payers (e.g. insulin application via the pulmonary route). 

New technologies are also addressing the pulmonary delivery of the new biotherapeutics , i.e. the products of biotechnology and molecular biology such as peptides, proteins and gene therapies which have been described in detail in Chapter 1 (Section 1.6). Biopharmaceuticals under investigation for potential pulmonary delivery include those for local, and systemic, effects (Table 10.4). 

Cells by themselves or by secreting pharmacologically active substances may have effects on the CNS, cardiac, respiratory, renal, or GI systems. Safety pharmacology should therefore be considered on a case-by-case basis depending on the specific characteristics of the cell-based product [52], In general, specific assessments are made as part of the toxicology assessments rather than as stand-alone studies consistent with the assessments made with protein-based biopharmaceuticals [50]. The fundamental physiological differences (e.g., total blood volume,pulmonary capillary surface area, and volume) should... 

Pharmacokinetic and Biopharmaceutical Factors Important for Pulmonary Targeting... 

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