Definition：

Aerosol means that the drug-containing, emulsion or suspension is packaged together with a suitable propellant in a pressure-resistant container with a special valve system. When in use, the content of the propellant is sprayed as a mist. Inhaled in the lungs or sprayed directly to the mucosa, skin and space disinfection preparations.

Classification：

Decentralized system

1. Solution aerosol: The solid or liquid drug is dissolved in the propellant to form a uniform solution. After the spray, the propellant volatilizes, and the drug reaches the action site in the state of solid or liquid particles.
2. Suspension aerosol: The solid drug is dispersed in the propellant in the form of particles to form a suspension. After the spray, the propellant volatilizes and the drug reaches the action site in the state of solid particles. Such aerosols are also called powder aerosols.
3. Emulsion-type aerosol: liquid drug or drug solution and propellant (insoluble liquid) form W/O or O/W Type emulsion. The O/W type is ejected in the form of foam as the internal phase propellant vaporizes during injection, and the W/O type follows the external phase propellant vaporizes to form a liquid stream.

By route of administration:

1. Inhalation aerosol: refers to medicinal solution, suspension or emulsion, together with suitable propellant or liquefied mixed propellant, sealed in pressure-resistant container with fixed valve system and certain pressure. The pressure of the propellant ejects the contents as a mist and inhales the preparation deposited in the lungs by the mouth. It is also commonly called pressure metered dose inhaler. The pressing valve can quantitatively release the active substance, the medicine is dispersed into particles or mist droplets, and inhaled through the respiratory tract to exert local or systemic therapeutic effects.
2. Non-inhalation aerosol: such as aerosol for skin and mucosa. Aerosols for skin are mainly used to protect wounds, clean and disinfect, local anesthesia and hemostasis. Nasal aerosol refers to a formulation deposited in the nasal cavity by nasal inhalation. Aerosols for nasal mucosa are used for the administration of some protein and peptide drugs and can exert systemic effects. Aerosols for vaginal mucosa are usually O/W foam aerosols. They are mainly used to treat vaginitis caused by microorganisms and parasites, and can also be used for birth control
3. External aerosol: refers to the aerosol used for skin and space disinfection

Application:

Aerosols can be used for local or systemic treatment. Local therapeutic effects such as: Yansukang aerosol for the treatment of pharyngitis, compound naphazoline spray for the treatment of rhinitis, compound metronidazole aerosol for the treatment of vaginitis, and lidocaine aerosol for local anesthesia and pain relief; Systemic therapeutic effects such as: glucocorticoid budesonide aerosol, antianginal nitroglycerin aerosol, antipyretic and analgesic indomethacin aerosol, etc..