Development of a biorelevant dissolution method for inhalation products: Proof of concept using drugs with diverse solubilities.

Background and purpose: Due to their unique application and action, inhalation products require specific quality tests, such as Uniformity of Delivered Dose and Aerodynamic Assessment of Fine Particles. While there's no current official requirement for dissolution tests, new draft guidelines are introducing them as a supportive or required measure; however, a universally accepted methodology for such testing remains elusive. The aim of the present study was to explore the discriminatory ability and Experimental approach: The applied experimental approach to biopharmaceutical characterization of inhalation products involved developing a biorelevant method for testing the dissolution rate of the selected active substances. Seven commercially available products, formulated as pressurized metered dose inhalers, containing either salmeterol xinafoate or beclomethasone dipropionate, have been studied. The research strategy combined in vitro testing within silico simulations. Key results: The developed dissolution method did not detect significant differences in the case of products containing highly soluble salmeterol, but it did reveal differences for products containing poorly soluble beclomethasone dipropionate. Moreover, a correlation was identified between the dissolution test results and absorption constants for beclomethasone dipropionate. Conclusion: The obtained results indicated that the investigated products would not be considered bioequivalent based on the aerodynamic particle size distribution. It was demonstrated that a discriminative dissolution method can be developed through a well-established paradigm of dissolution testing, while taking into account the specificities of the inhalation route of administration.