Production of spray dried salbutamol sulphate for use in dry powder aerosol formulation

Abstract

Salbutamol sulphate particles, for use in dry powder aerosol formulation, were prepared by spray drying, using a Büchi 190 mini spray dryer. The spray drying parameters were investigated in relation to particle size and yield of the resultant powder. Important factors were determined using a 2 4 factorial statistical design. The four factors investigated were pump speed, aspirator level (the rate at which the drying air is pulled through the dryer), inlet temperature and the concentration of the aqueous salbutamol sulphate solution dried. Spray drying conditions were chosen based on results from the experimental design and working knowledge of the spray dryer, to produce a batch of salbutamol sulphate powder on which further studies were performed. The physicochemical properties of spray dried salbutamol sulphate were compared to those of the micronised drug. Infrared spectroscopy, X-ray diffraction, appearance, particle size analysis (including aerodynamic diameter) and powder flow were investigated. It was found that spray drying produced spherically shaped particles of salbutamol sulphate having a mass median diameter of 4.5 μm (laser diffraction), mean Feret's diameter (image analysis) of 1.58 μm and a mass median aerodynamic diameter of 9.7 μm (cascade impaction), i.e., particles sufficiently small in diameter for use in inhalation formulation. The spray dried material was seen to perform as well as the micronised material in most cases with the exception of powder flow properties, where performance was slightly poorer.