PRODUCTION OF SPRAY-DRIED SALBUTAMOL SULFATE FOR USE IN DRY POWDER AEROSOL FORMULATION

Salbutamol sulphate particles, for use in dry powder aerosol formulati on, were prepared by spray drying, using a Buchi 190 mini spray dryer. The spray drying parameters were investigated in relation to particle size and yield of the resultant powder. Important factors were determ ined using a 2(4) factorial statistical design. The four factors inves tigated were pump speed, aspirator level (the rate at which the drying air is pulled through the dryer), inlet temperature and the concentra tion of the aqueous salbutamol sulphate solution dried. Spray drying c onditions were chosen based on results from the experimental design an d working knowledge of the spray dryer, to produce a batch of salbutam ol sulphate powder on which further studies were performed. The physic ochemical properties of spray dried salbutamol sulphate were compared to those of the micronised drug. Infrared spectroscopy, X-ray diffract ion, appearance, particle size analysis (including aerodynamic diamete r) and powder now were investigated. It was found that spray drying pr oduced spherically shaped particles of salbutamol sulphate having a ma ss median diameter of 4.5 mu m (laser diffraction), mean Feret's diame ter (image analysis) of 1.58 mu m and a mass median aerodynamic diamet er of 9.7 mu m (cascade impaction), i.e., particles sufficiently small in diameter for use in inhalation formulation. The spray dried materi al was seen to perform as well as the micronised material in most case s with the exception of powder flow properties, where performance was slightly poorer.