For myself, I see the promotion of such methodologies through my teaching activities as a legacy I want to leave, since ultimately it would be excellent if key examples of this type of methodology become captured in informative chapters on various aspects of inhaler testing in the pharmacopoeias.
In this way, newcomers to the profession can have ready access to methods that are informative about the properties of the aerosols when generated in ways that are closer to actual use than the current methods (which are needed for product quality control) do. Furthermore, such standard methods would then be divorced from individual companies and acquire more general applicability.
Another example of an excellent development is the “Alberta” series of idealized oropharynxes that have been developed by Prof. Warren Finlay and colleagues at the University of Alberta, Edmonton. Each version (adult, child and likely an infant shortly to come) captures the aerosol deposition characteristics of the highly complex anatomic geometry in a simplified pathway that can be manufactured easily, in much the same way as is done for the standardized right-angle bend Ph.Eur./USP throat. Importantly, in the context of achieving better harmony between laboratory and clinical data, each idealized throat is an age-appropriate model that is a much better representation of reality than the pharmacopeial throat.
Then closer to home, there are the ADAM (Anatomic Delivery of Aerosol Model) soft faces with realistic upper airways that we have developed for the past 10 years at TMI and which I hope will be commercially available one day. The third generation of models completes the picture in terms of simulating reality associated with the testing of inhalers with facemasks. This is because we have realized the mechanically responsive nature of the skin surface where the mask ‘lands’ when applied, as well as simulating a close realization of the underlying soft tissues in addition to the introduction of some supporting bone structure at relevant locations.
Furthermore, we have combined each face with its age-appropriate upper airway so that as well as being able to determine the API mass emitted from the inhaler, we can accurately establish the mass delivered to the carinal region. This is getting about as close to reality in the laboratory as is possible to do without the use of volunteers to inhale the aerosolized medication, with a filter at the mouth/nose to collect the particulate for assay and prevent it entering the respiratory tract of the volunteer.
This is still a work-in-progress but I am confident that the ADAM-III approach uses appropriate technology that has only recently become available for creating replicas. I’ve also talked to a number of people who see that approach of mimicking the skin and the underlying soft tissues as being the right way to go. So these are exciting developments that I think will actually move the field forward.
