Impaction force and velocity are important parameters for measuring an aerosol spray, however, they are not as well understood as other methods used in testing these devices.
Thus the US Food and Drug Administration (FDA) is now encouraging the development of new methods.
Copley Scientific has been developing a new product - Spray Force Tester (SFT) 1000 - to measure the spray force of MDIs and nasal sprays at a range of distances from the MDI mouthpiece, for research and quality control purposes.
"Control and optimisation of the spray force may prove to be an important parameter in evaluating inhaler performance," said Copley Scientific spokesperson Mark Copley.
Spray force is closely related to aerosol deposition.
Unwanted particle deposition in the throat is of major concern to inhaled drug developers as it can cause discomfort to patients.
"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," said Copley.
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.
Encouraged by this, Coley has now enlisted the help of contract analytical services firm Melbourn to generate preliminary data on the SFT 1000, which will be available for discussion at Respiratory Drug Delivery (RDD) Europe, to be held in Paris in April.
Melbourn is a specialist in the testing of inhaled products and was the first contract laboratory in the UK to offer inhaler testing with an electronic lung developed by consultants TTP.
"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," said Melbourn spokesperson Mark Hammond.
"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."