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Laboratory scale spray drying of lactose: A review

best@buchi 57/2010
Best@Buchi_57_Laboratory Scale Spray Drying of Lactose - A Review

Inhalable applications

• Spray drying is able to produce stable, efficient and inhalable dry lactose powder systems for respiratory delivery with adequate particle size and shape for deep lung deposition.

Spray drying versus jet milling

• Spray drying and jet milling showed insignificant differences in fine lactose particle size of the same formulations.
• Spray dried particles showed higher dispersibility compared to jet milled particles due to spherical shape and smaller surface contact area.
• The dissolution and inhalation behaviour of spray dried powder is even more advantageous than that of mechanically micronized powder. Spray dried particles free themselves from the large lactose carrier particles as easily as mechanically micronized particles.

Aerosol properties and dispersibility

• The aerosol properties and dispersibilty of spray dried powders can be enhanced by incorporation of suitable excipients, such as NaCl salt  or amino acids before spray drying, allowing the development of stable and viable formulations for pulmonary inhalation.

Amorphous/crystalline structure

• The rapid solidification in spray drying causes lactose in suspension to become amorphous. Various polymorphic proportions can be manufactured by selection of the appropriate feed concentrations.
• Spray drying process conditions may be utilized to alter the final spray dried lactose product, where the inlet gas temperature has a significant impact on the crystallinity.
• The presence of polyethylene glycol promotes crystallization of lactose when the two components are co-spray dried.
• Crystallization is favoured by a low molecular weight and a high concentration of PEG.

Nanoparticles

• Incorporation of nanoparticles into respirable carrier particles can be a straightforward process when formulating via spray drying. Spray dried nanoparticle aggregates are capable of serving as micrometersized carriers of nanoparticulate drugs. This facilitates the nanoparticle delivery to the lung for potential inhaled drug delivery applications in Dry Power Inhalers.
• The Nano Spray Dryer B-90 provides a novel spray drying technique in laboratory scale to prepare submicron particles for pulmonary delivery dry powder formulations.