41. Pharmaceutical Aerosol Sprays for Drug Delivery to the Lungs

Respiratory illnesses are commonly treated with drugs delivered to the lungs as an inhaled aerosol. The inhaled aerosol route sometimes offers advantages over other routes such as injection or oral delivery. These advantages include rapid and predictable onset of action of drug, decreased adverse reactions, as well as safe and convenient delivery. However, the design of a device and formulation for reliable delivery of a pharmaceutical compound as an inhaled aerosol is more difficult than most other delivery routes. This is because of the need to transform the active ingredient into an aerosol having particle sizes of a few micrometers in diameter that is then supplied to the patient’s mouth upon inhalation. Devices that can create sprays with particles in the micrometer size range, but which remain portable, inexpensive to manufacture, easy to use by patients, and are robust enough to withstand patient use, are relatively few in design. Indeed, at present only four basic spray production mechanisms are currently in use on the clinical market for drug delivery to the lungs: pressurized release of a volatile propellant, colliding liquid jets, air-blast atomization and high frequency vibration methods. While other methods have undergone development (e.g., Rayleigh breakup of an extruded liquid jet [1]; high voltage electrosprays [2]), they have not yet reached market release. In the following we consider the four clinically available methods.