ABSTRACT
The inhalation of drugs provides the most direct noninvasive route either for treating respiratory disorders topically or for administering drugs systematically. To ensure that the drug reaches the lungs, it must be administered as an aerosol. This means that the required amount of drug per application consists of drug particles, either solid or liquid droplets in a size range of 1-5 µm, which are inhaled by the patient. In the past, pressurized metered-dose inhalers (pMDIs) have been popular devices for generating inhalable aerosols. These devices depend on chemical propellants to generate an aerosol from a drug solution or suspension; however, their future is now uncertain.
