Particle engineering to stabilise microsuspensions via electrostatic and conventional spray drying

Formulating suspensions that will remain stable throughout their shelf-life without changes in particle size is critical for pharmaceutical products. Suspension instability impacts the final product quality, hence methods to enhance the stability of pharmaceutical suspensions over their storage period at room temperature are sought after. In this investigation, two drying techniques – electrostatic spray drying (ESD) and conventional spray drying (SD) – are evaluated as potential methods to enhance the stability of two pharmaceutical suspensions: an indomethacin suspension and an API D suspension, throughout their shelf-life, in powder form, at room temperature. This may provide an alternative pathway to stabilising suspensions for reconstitution, potentially bringing down cost of goods due to improved stabilisation at room temperature and thereby eliminating the need for cold storage. Process optimisations were performed and the reconstituted suspensions were analysed to determine whether their properties were retained and comparable to the original suspensions. The results showed that the optimised ESD and SD parameters produced samples with a moisture content of less than 0.4 % w /w and the purity of the optimised samples from both techniques was within 95–105 % w/w. Upon reconstitution, both SD and ESD suspensions had comparable PSD, to each other, and to the original milled suspension. Furthermore, this investigation showed that ESD and SD were successful in producing spray dried powder of two pharmaceutical suspensions, which remained stable for 1 month at 25 °C/60 % RH, and could be resuspended whilst retaining the original suspension properties.