Dissolution Testing For Inhaled drugs - Pharmaceutical Technology

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Dissolution Testing For Inhaled drugs
Although there are no regulatory requirements or established pharmacopoeial techniques for the dissolution testing of inhaled drugs, such testing can potentially open up the opportunity to tailor formulation properties. The authors explain how a new technique using standard dissolution test equipment in combination with US Pharmacopeia methods for the dissolution testing of solid dosage forms can be used to differentiate the solubility of orally inhaled products.

Pharmaceutical Technology Europe
Volume 22, Issue 11


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.


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

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)


1. European Pharmacopoeia 6.0, Section 2.9.18 'Preparations for inhalation: aerodynamic assessment of fine particles' p.299 (2008).

2. V.A. Gray et al., Pharmacopeial Forum, 34(4) (2008).

3. T. Riley et al., In vitro method for determining the dissolution rate of inhalation aerosols at Respiratory Drug Delivery (May 2008; AZ, USA).

4. R.J. Mayank and M. Ambikanandhan, AAPS PharmSciTech, 2(4) article 25 (2001).

5. T.B. Patel, pharmainfo.net/, 5(4) (2007).

6. O.R. Moss, Health Physics, 36, 447–448 (1979).

7. N.M. Davies and M.R. Feddah, Int J Pharm., 255(1-2), 175–187 (2003).

8. YJ. Son and J.T. McConville, Development of a standardized dissolution test for inhalable formulations at Respiratory Drug Delivery (May 2008; AZ, USA).

9. YJ. Son and J.T. McConville, Inhalation, 2(6) (2008).

10. YJ. Son et al., Dissolution Technologies, 17(2), 6–13 (2010).

11. US Pharmacopeia Volume 1, Apparatus 5 for Dry Powder Inhalers, p.216–220 (2009).

12. European Pharmacopoeia 6.0, Section 2.9.18: Apparatus E: Procedure for powder inhalers p. 297–300 (2008).

13. V.Marple et al., Journal of Aerosol Medicine, 16(3), 301–324 (2003).

14. M. A. Launois-Surpas et al., Colloid Polym. Sci., 270(9), 901–911 (1992).

15. V.P. Shah et al., Dissolution Technologies, 15(6), 889–896 (1998). http://www.dissolutiontech.com/DTresour/899Art/DissProfile.html


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