Learning Objectives

• Different propellants used in aerosol preparations
• Advantages and disadvantages of the various propellants
• Nomenclature of liquefied gas propellants
• Principle of operation of aerosols with liquefied gases and compressed gases as propellants

A propellant is responsible for developing the pressure within the container and in combination with other components it expels the product in the desired physical form like spray, mist or foam.

Propellants may be broadly classified as follows:

1. Compressed gasses
2. Liquefied gases

The types of propellants used for different pharmaceutical applications are listed in Table 12.1.

 

Table 12.1 Types of Propellants for Different Applications

Application	Types of propellants
Oral and inhalation	Trichloromonofluoromethane (propellant 11), dichlorotetrafluoroethane (propellant 114) and dichlorodifluoromethane (propellant 12).
Topical	Propane, butane, isobutane and compressed gases like nitrogen and carbon dioxide.