鸡的英语单词Aerosols
Pharmaceutical aerosols are products that are packaged under pressure and contain therapeutically active ingredients that are relead upon activation of an appropriate valve system. They are intended for topical application to the skin as well as local application into the no (nasal aerosols), mouth (lingual aerosols), or lungs (inhalation aerosols). The products may be fitted with valves enabling either continuous or metered-do delivery; hence, terms” [DRUG] Metered Topical Aerosols,” ” [DRUG] Metered Nasal Aerosols,” etc.
The term”aerosol” refers to the fine mist of spray that results from most pressurized systems. However, the term has been broadly misapplied to all lf-contained pressurized products, some of which deliver foams or misolid fluids. In the ca of Inhalation Aerosols, the particle size of the delivered medication must be carefully controlled, and the average size of the particles should be under 5 何足挂齿的意思μｍ. The products are also known as metered-do inhalers (MDIs). Other aerosol sprays may contain particles up to veral hundred micrometers in diameter.
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The basic components of an aerosol system are the container, the propellant, the concentrate containing the active ingredient(s), the valve, and the actuator. The nature of the components determines such characteristics as particle size distribution, uniformity of do for metered valves, delivery rate, wetness and temperature of the spray, spray pattern and velocity or plume geometry, foam density, and fluid viscosity.
Types of Aerosols
Aerosols consist of two-pha (gas and liquid) or three-pha (gas, liquid, and solid or liquid) systems. The two-pha aerosol consists of a solution of active ingredients in liquefied propellant and the vaporized propellant. The solvent is compod of the propellant or a mixture of the propellant and cosolvents such as alcohol, propylene glycol, and polyethylene glycols, which are often ud to enhance the solubility of the active ingredients.
Three-pha systems consist of a suspension or emulsion of the active ingredient(s) in addition to the vaporized propellants. A suspension consists of the active ingredient(s) tha
清炖羊肉的做法及配料t may be disperd in the propellant system with the aid of suitable excipients such as wetting agents and/or solid carriers such as talc or colloidal silicas.
A foam aerosol is an emulsion containing one or more active ingredients, surfactants, aqueous or nonaqueous liquids, and the propellants. If the propellant is in the internal (discontinuous) pha (i.e., of the oil-in-water type), a stable foam is discharged; and if the propellant is in the external (continuous) pha (i.e., of the water-in-oil type), a spray or a quick-breaking foam is discharged.
Propellants成都市安全教育平台
宫崎骏动画图片The propellant supplies the necessary pressure within an aerosol system to expel material from the container and, in combination with other components, to convert the material into the desired physical form. Propellants may be broadly classified as liquefied or compresd gas having vapor pressures generally exceeding atmospheric pressure. Propellants within this definition include various hydrocarbons, especially halogenated derivatives of methane, ethane, and propane, low molecular weight hydrocarbons such a
s the butanes and pentanes, and compresd gas such as carbon dioxide, nitrogen, and nitrous oxide. Mixtures of propellants are frequently ud to obtain desirable pressure, delivery, and spray characteristics. A good propellant system should have the proper vapor pressure characteristics consistent with the other aerosol components.
Valves
The primary function of the valves is to regulate the flow of the therapeutic agent and propellant from the container. The spray characteristics of the aerosol are influenced by orifice dimension, number, and location. Most aerosol valves provide for continuous spray operation and are ud on most topical products. However, pharmaceutical products for oral or nasal inhalation often utilize metered-do valves that must deliver a uniform quantity of spray upon each valve activation. The accuracy and reproducibility of the dos delivered from metering valves are generally good, comparing favorably to the uniformity of solid dosage forms such as tablets and capsules. However, when aerosol packages are stored improperly, or when they have not been ud for long periods of tim
e, valves must be primed before u. Materials ud for the manufacture of valves should be inert to the formulations ud. Plastic, rubber, aluminum, and stainless steel valve components are commonly ud. Metered-do valves must deliver an accurate do within specified tolerances.
Actuators
青岛供暖An actuator is the fitting attached to an aerosol valve stem, which when depresd or moved, opens the valve, and directs the spray containing the drug preparation to the desired area. The actuator usually indicates the direction in which the preparation is dispend and protects the hand or finger from the refrigerant effects of the propellant. Actuators incorporate an orifice that may vary widely in size and shape. The size of this orifice, the expansion chamber design, and the nature of the propellant and formulation influence the delivered do as well as the physical characteristics of the spray, foam, or stream of solid particles dispend. For inhalation aerosols, an actuator capable of delivering the medication in the proper particle size range and with the appropriate spray pattern and plume geometry is utilized.
