![]() ![]() ![]() Dry powder inhalers have even become the first choice of inhalation devices in European countries ( Marriott et al., 2012).They are a widely accepted inhaled delivery dosage form where they are currently used by an estimated 40% of patients to treat asthma and chronic obstructive pulmonary disease ( Atkins, 2005). Dry powder inhalers and dry powder inhalation technology became the second most frequently used inhalation devices for pulmonary drug administration after Montreal Protocol in 1987 in limitation of using CFC in products. Among these, DPI appears to be the most promising for future use ( Todo et al., 2001).They are propellant-free, portable, easy to operate and low-cost devices with improved stability of the formulation as a result of the dry state( Carpenter et al., 1997 Prime et al., 1997).Spinhaler®, the first dry powder inhaler, came into the market in 1970 and since then a new are started in the subject of pulmonary drug delivery. Pressurized metered-dose inhaler (MDI), nebulizer and dry powder inhaler (DPI) are main delivery systems in pulmonary delivery ( Timsina et al., 1994). Several methodologies have been discussed. This chapter offers a perspective on current reported studies to modify carrier for its better performance. Therefore, the purpose of this chapter is to review the used carriers in inhalable formulations, their production and the impact of the physicochemical properties of carriers on carrier-drug dispersion is discussed in detail. This could be achieved by successful carrier selection and careful process optimization ( Pilcer et al., 2012). The main objective in the inhalation field is to achieve reproducible, high pulmonary deposition. The aerosolization efficiency of a powder is highly dependent on the carrier characteristics, such as particle size distribution, shape and surface properties. Dry powder formulations are usually prepared by mixing the micronized drug particles with larger carrier particles. The effective inhalation performance of dry-powder products is dependent on the drug formulation and the inhaler device. Particles with aerodynamic diameters between 1 and 5 μm are expected to efficiently deposit in the lung periphery ( Heyder et al., 1986). Particles larger than 5 μm are mostly trapped by oropharyngeal deposition and incapable of reaching the lungs while smaller than 1 μm are mostly exhaled without deposition ( Sakagami, 2006). Drug deposition in the lung is mainly controlled by its aerodynamic diameter ( Wolff et al., 1993). In contrast to injection therapy, inhalation therapy is not associated with pain and this should increase patient comfort and compliance, causing improved treatment outcome ( Laube, 2005). Following approving the first inhaled therapeutic macromolecule for systemic delivery, human insulin (Exubera™) by the Food and Drug Administration (FDA) and the European Agency for the Evaluation of Medicinal Products in 2006, the scientific community look for other candidates that would benefit from pulmonary delivery for systemic action ( Patton et al., 2004 Furness, 2005). Lack of first pass metabolism and less enzymatic activity make pulmonary delivery as an ideal administration route for extensively degraded drugs following oral delivery and for macromolecules, such as proteins and peptides, respectively( Hamishehkar et al., 2010 Rytting et al., 2008 Sakagami, 2006). In this case, lower dosages than by the oral route can be used with comparable effectiveness which will reduce unwanted side effects ( Timsina et al., 1994).The lung also provides a non-invasive route of delivery for the systemic circulation, due to its unique characteristics such as large surface area, thin epithelial barrier and high blood flow. Increasing prevalence of pulmonary diseases with high mortality and morbidity such as chronic obstructive pulmonary disease (COPD), asthma, cystic fibrosis, infectious diseases, tuberculosis and lung cancer, makes pulmonary drug delivery as a non-invasive and attractive approach for the local drug administration and treatment of these pathologies ( Marianecci et al., 2011). ![]()
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