• Jagdeep Shur, Harshal A Kubavat, Graham Ruecroft, David Hipkiss, and Robert Price.
• Pharmaceutical Surface Science Research Group, Department of Pharmacy and Pharmacology, University of Bath, Bath, UK.
• J. Pharm. Pharmacol. 2012 Sep 1; 64 (9): 1326-36.

ObjectivesThis study aimed to investigate the relationship between the mechanical properties of anhydrous and monohydrate ipratropium bromide (IB) crystals, their processing behaviour upon air-jet micronisation and aerosolisation performance in dry powder inhaler (DPI) formulations.MethodsIB monohydrate and anhydrous crystals were produced from seed crystals and supercritical carbon dioxide crystallisation, respectively. Young's modulus of anhydrous and monohydrate IB crystals was determined using nanoindentation. For air-jet micronised crystals, the physicochemical and surface interfacial properties via the cohesive-adhesive balance (CAB) approach were investigated. These data were correlated to in-vitro aerosolisation performance of carrier-based DPI formulations containing either anhydrous or monohydrate IB.Key FindingsParticle size and Young's modulus of both crystals were similar and this was reflected in their similar processing upon micronisation. Particle size of micronised anhydrous and monohydrate crystals were similar. CAB measurements of the micronised particles of monohydrate or anhydrous forms of IB with respect to lactose were 0.70 (R² = 0.998) and 0.77 (R² = 0.999), respectively. These data suggested that both samples had similar adhesion to lactose, which correlated with their similar in-vitro aerosolisation performance in DPI formulations.ConclusionsMonohydrate and anhydrous crystals of IB exhibited similar mechanical properties and interfacial properties upon secondary processing. As a result, the performance of the DPI formulations were similar.© 2012 The Authors. JPP © 2012 Royal Pharmaceutical Society.

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