Aerosol refers to a preparation in which medicine and propellant are jointly enclosed in a pressure-resistant container with a valve system, and when used, the medicine is to be ejected by the pressure of the propellant according to the valve system.
At present, medicinal aerosols are no longer restricted to the concept of forming "drug aerosols", but extend to various medicines that are pressure-packed. Such as three-phase pressure emulsion, vaginal spermicidal foam, spray, etc. are all included in the aerosol category. Due to the emergence of the dual packaging system, a French "oestrogel" for the treatment of women's menopausal syndrome, it discharges gel when used, and is also classified as a medicinal aerosol.
Medicinal aerosols can be divided into three types according to the dispersion system used: solution type, suspension type and emulsion type. In my country, medicinal aerosols can also be divided into three types according to medical purposes: one is skin aerosols. Aerosols absorbed through the skin are also called external aerosols. The second is the aerosol for cavity mucosa, which is absorbed through cavity and mucosa, such as oral cavity, nasal cavity and vagina. The third is aerosol inhaled through the respiratory tract. The first two are collectively referred to as non-respiratory inhalation aerosols.
Medicinal aerosols can discharge mist particles, bubbles, liquid streams or gels and creams during use, not necessarily mist particles, but one of the common features of these aerosols is that they are all pressure-packed. The drug in the form is driven out of the container by pressure to reach the drug site to play a role.
We know that propellants are indispensable for aerosol products. Propellants act as a motive force in aerosols, are a source of pressure and also serve as pharmaceutical solvents or diluents. At present, propellants can be divided into two types: liquefied gas and compressed gas. Liquefied gas includes fluorocarbons and hydrocarbons. Such as chlorofluoroalkanes, propane, n-butane, etc.; compressed gas such as carbon dioxide, nitrogen and other emotional gases. Hydrocarbons are highly toxic, flammable, and explosive, which brings difficulties to the process. Some drugs in the compressed gas cannot achieve the spray effect.
Due to the above reasons, the application of these two propellants is limited. Therefore, chlorofluoroalkanes are mainly used for medicine. There are mainly F11, F12, and F114. However, since the “ozone depletion hypothesis” put forward by professors and doctors of the University of California in June 1974, various countries have expressed concern about Freon propellants, although medicinal aerosols have been affected. Special exemptions, but as the Montreal Treaty’s ban on production, sales and use is approaching, environmentalists in various countries are calling for the early implementation of the Montreal Treaty. Medicinal aerosols are still under heavy pressure. All chlorofluorocarbon producers and major pharmaceutical companies are actively looking for alternatives to Freon.
The ideal new propellant to replace Freon should have the following characteristics:
At room temperature, its vapor pressure is greater than atmospheric pressure. Biological and chemical inertness, low ozone depletion and low-temperature greenhouse potential, proper solubility.
The current promising alternatives are dry inhalation aerosols: difluoroethane, HFC-134a, HFC-142b, HCFC-22.
For external aerosols: propane butane, dimethyl ether, HCFC-22, HFC-142b.
Used in binary packaging system: compressed gas.
