Chemical Imaging by Raman Spectroscopy: A Powerful Analytical Technique for Surface Morphology Investigation of Inhaled Products

Lluis Pausas, Memory Jiri, Daniel Ross & Mridul Majumder

M2M Pharmaceuticals Ltd., The Gateway Building, 1 Collegiate Square, Thames Valley Science Park (TVSP) Reading RG2 9LH, UK


Pulmonary disorders are a growing healthcare problem that are expected to worsen as the population ages. Regular use of inhaled bronchodilators to prevent and relieve symptoms is the mainstay of many pulmonary disorders. Inhalers may contain drugs either alone or combined with other Active Pharmaceutical Ingredients (API), for example, the long-acting beta 2-agonist and corticosteroid inhaler, which is mainly used for exacerbated chronic obstructive pulmonary disease (COPD)[i].

Particle interactions are of great importance where the dispersion of API particles from carrier particles is critical for lung deposition. Poor API homogeneity is undesirable since homogenous drug content is essential to achieve consistent emitted dose of the drug during inhalation2. Moreover, not only must the force of adhesion be strong enough to maintain the blend homogeneity during manufacturing process, but it must also allow the detachment on inhalation to effectively deposit API into the deep lung. Thus, blending API with carrier is a critical stage that determines the blend homogeneity and is the first step towards obtaining the final quality of the powder blend3. Raman spectroscopy and its powerful chemical imaging capability enables understanding of many of these key attributes for inhaled formulations4.

In this study, two marketed inhaler products, used for the treatment of exacerbated COPD, were compared by chemical imaging using Raman spectroscopy.

Key Message

Chemical imaging by Raman spectroscopy might be a suitable technique for the analysis and monitoring of inhalation formulations, especially the distribution in the matrix, percentage of each component present in the formulation and particle size distribution of each component. This could be applied as an analytical technique for inhaled product development.