Conclusion
The possibility of tailoring release profiles of OIP formulations for more controlled
in vivo
delivery brings with it the need for dissolution testing for inhaled actives. Researchers at the University of Texas have
developed a possible solution to meet this need that involves collection of a suitable dose using an NGI followed by dissolution
testing with standard USP method 5 equipment (paddle over disc). Subsequent development into a commercially available product
provides a solution for exploration of the solubility of OIP formulations. The NGI dissolution cup enables capture of that
fraction of the emitted dose of interest for dissolution studies; the associated membrane holder presents the sample in an
ideal form for "paddle over disc" testing.
Using this novel apparatus, experimental studies were carried out to investigate the influence of different parameters on
the measured dissolution profiles of BD and AS. These tests highlight the ability of the technique to sensitively differentiate
the different solubility characteristics of OIP formulations, but also underline the importance of considering variables such
as drug loading and dissolution media composition in the development of appropriate test procedures.
* Statistical differences between release rates were compared using a similarity factor. This is an established, relatively
simple technique for comparing the similarity of different dissolution profiles. While the authors have not included a full
description of the method here, reference 15 provides significant detail. Generally speaking, a similarity factor of between
50 and 100 indicates sameness of equivalence in the two curves. Figures of less than 50 suggest a marked difference.
Acknowledgement
This article has been developed using figures in a paper published in
Dissolution Technologies
. The authors would like to thank the editorial advisory board of Dissolution Technologies for permission to use material from the paper, available at
http://www.dissolutiontech.com/.
Mark Copley is Sales Director at Copley Scientific, Colwick, Nottingham UK NG4 2JY.Tel. +44 (0)115 961 6229 m.copley@copleyscientific.co.uk
Yoen-Ju Son is Visiting Research Scientist at College of Pharmacy, University of Texas at Austin (TX, USA).
Jason McConville is Assistant Professor, Director of InstrUcTex, at College of Pharmacy, University of Texas at Austin (TX, USA)
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