Learning Objectives

• Stability aspects regarding the compatibility of product and container
• Stability of the valve with the product

The complete aerosol package includes both the product and the container. Hence while studying the stability aspects of aerosols, both the effect of the product on the container and the effect of the container on the product should be studied. Moreover, due to the variety of materials used in making an aerosol valve and container, it is essential to study the effect of these different materials on the product individually as well as collectively. Several container coatings as well as valves with different sub-components may be studied so that any reaction between the component and the product may be detected.

Testing of pharmaceutical aerosols is carried out based on the component namely:

• The product concentrates which includes the propellant
• The container
• The valve assembly.

The stability testing of the product concentrate includes determination of several physico-chemical parameters such as vapor pressure, spray rate of the valve, pH, density or specific gravity, refractive index, viscosity, total weight, assay of active ingredients, chromatography curves, color and odor. The compatibility of the product with the container is tested by keeping the contents in close contact with the different parts of the container.

Stability of the container is checked by chilling the container to a temperature of 0°F or less and taking out the contents. The container is examined insides for any signs of corrosion. The containers that have been lacquered on the insides are examined for softening of the lacquer. Plastic containers are checked for leaching or sorption.

The different valve components are checked for any evidence of corrosion especially the mounting cup. The other valve components are checked for softening, cracking, elongation or distortion. These problems can lead to the improper functioning of the valve during usage and hence should be corrected during the initial stage itself.