Definition Of Terms

The terms used to describe the equipment in the manufacture of pressurized-pack pharmaceutical aerosols may not be within everyone's experience. Therefore, it is appropriate to define some of these terms before discussing packaging in detail.

The term concentrate or concentrate product has been defined as all of the components that are included in the aerosol formulation with the exception of the propellant [6-8]. The concentrate would, therefore, include the active ingredient, surfactant, solvent, and any additional materials, such as antioxidants or antimicrobials. It may also include low-vapor-pressure propellants such as propellant 11 or cosolvents such as ethanol.

Propellants are generally high-vapor-pressure CFCs and HFAs. Until recently the most common examples were the CFC propellants 11, 12, and 114. These propellants have been superceded in new formulations by HFA 134a and 227. The HFA propellants are intended to replace CFC 12. Some of the physicochemical characteristics of these propellants are shown in Table 1. The use of atmospheric-ozone-depleting CFCs in inhalers was a hotly debated issue in the late 1980s and early 1990s [11,12]. This may be followed in the professional literature [13-23]. It is now clear that CFCs will

Table 1 Vapor Pressure and Molecular Weights of Common CFC Propellants

Propellant

Vapor pressure Molecular Number (psia) at 25°C Weight

Trichloromonofluoromethane Dichlorodifluoromethane Dichlorotetraf luoroethane Tetrafluoroethane Heptafluoropropane

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