Tests for foreign particles in metered-dose aerosols

A simple method for the determination of foreign particular matter in metered-dose aerosols (MDA's) has been developed. The method compares favourably with a procedure currently used in pharmaceutical industry and has the advantage of providing information on container to container variation. A linear relationship between log particle count and particle size was found for a number of MDA's, although there was considerable product-to-product variation. On the basis of the results obtained in this study, commercially available MDS's would in general comply with a limit for foreign particles greater than 100 micrometers of not more than 150 particles per container with the sum of the mean count and twice the standard deviation not more than 200.