Impaction force and velocity are important parameters for describing an aerosol plume, but are not as well understood as other methods used in testing nasal sprays and metered-dose inhalers (MDIs)
As interest grows from the US Food and Drugs Administration and others in these tests, Melbourn Scientific and Copley Scientific are to collaborate on novel research to evaluate the spray force for a range of MDIs and nasal sprays.
Spray force is closely related to aerosol deposition.
Copley Scientific has been developing a new product to measure the spray force of MDIs and nasal sprays at a range of distances from the MDI mouthpiece.
Mark Copley, sales manager of Copley Scientific, believes that industry data will be of interest to developers of inhaler devices.
He comments: "Unwanted throat deposition is of major concern to inhaled drug developers, as this is the discomfort experienced by patients due to particle impaction on the back of the throat.
"Control and optimisation of the spray force, relative to the throat geometry, may prove to be an important parameter in evaluating inhaler performance".
"The FDA division of pharmaceutical analysis has shown interest in this technique and I don't think it will be long before the FDA encourages pharmaceutical companies to generate this type of data as part of their drug submissions.
"We have developed the Spray Force Tester SFT 1000, which is a product designed to perform spray force tests for research and quality control purposes, and we will be working with Melbourn to generate preliminary data for a range of nasal sprays and MDIs".
The role of impaction force was discussed in a paper presented at the 2006 FDA Science Forum, by Guo and Doub.
The authors suggested that impaction force, which is directly related to spray velocity, may provide a better way to evaluate in vitro equivalence in support of new drug applications (NDAs) or abbreviated new drug applications (ANSAs) for orally inhaled and nasal drug products, as it is more closely related to patient sensation and aerosol deposition than the current parameters.
Melbourn Scientific provides contract analytical services to the pharmaceutical industry and has a strong track record in testing of inhaled products; it was the first contract laboratory in the country to offer inhaler testing with the electronic lung developed by consultants TTP and has continued to innovate.
Mark Hammond, business development director, comments that the company is always interested in evaluating new technologies.
"We have seen continued interest in our analytical support for the development of inhaled products, and as such we endeavour to work with new techniques and technologies which help improve our characterisation of device performance.
"We hope that the data obtained through this research will enable our clients to make informed decisions on the applicability of spray force testing for their devices".
