Test method for evaluation of loss of prime in metered-dose aerosols

A new test method is described for assessing the loss of prime in metered-dose aerosols. Two representative metered-dose valve designs and two storage positions were used to assess the utility of this test method at three different sites. Loss of prime, defined as a valve delivery 15% below the mean, was detected in three of the four test configurations. The first significant loss of prime in this study was observed at the two-week time point for valves without drain tanks stored in the upright position. Onset of loss of prime was shown to be dependent on valve design as well as storage position, thus alternate valves or storage conditions should yield different results. This test method appeared to be reproducible over the three test sites, with a slight variation in results attributed to differences in storage conditions and agitation during sample handling. This test method intentionally excluded agitation which is in sharp contrast to the normal "shake well before use" instruction to the patient. Following one priming actuation, all of the valves returned to their mean valve delivery.