Development of dry powder inhaler formulations for drug delivery systems

Oral or parenteral administration of drugs to treat lung diseases is met with several challenges, including delivery of the active substance in insufficient amounts, inability to produce the desired effect at the target region, and severe systemic side effects. The best solution to this problem is the pulmonary administration of drugs. Although several formulations for administering inhaled medications such as nebulizers and metered-dose inhalers are available, dry powder inhalers (DPIs) are particularly advantageous owing to their ability to administer a high amount of active ingredient in a short time and higher stability than that of aqueous formulations. Similar to all inhaler formulations, one of the major problems encountered in DPIs is the inability of the active substance to reach the peripheral lungs in sufficient quantity. Moreover, reproducible results are difficult to obtain due to different inhalation capacities among individuals. This review provides the readers with a general perspective on different approaches used in developing various DPIs. Moreover, the review discusses the aerodynamic parameters of these formulations. DPIs developed with novel manufacturing methods are safe with increased therapeutic efficacy, as demonstrated by the results of their in vitro and in vivo safety and efficacy studies. These findings indicate that DPIs could serve as a promising modality for pulmonary drug delivery.