Spray-dried composite particles of lactose and sodium alginate for direct tabletting and controlled releasing

A novel composite particle suitable for the filler of controlled-release matrix tablets was prepared by spray-drying an aqueous solution of a-lactose monohydrate and sodium alginate. The spray-dried (SD) particles had an excellent flowing property due to their spherical shape and sharp particle size distribution. When the SD particles were compressed into a tablet in a compressing pressure range of 100-400 MPa using an Instron-type hydraulic press, the tensile strength of compacts was much higher than that of a commercial lactose for direct tabletting and a physical mixture of lactose and sodium alginate particles with the same formulating ratio as for the SD particles. The improvement in compressibility of the SD particles was attributed to an increased deformability of particles with a decrease in crystallinity of lactose. Thermal stability of amorphous form of lactose in the SD particles determined by differential scanning calorimetry was dramatically enhanced with the presence of sodium alginate in the particles. It was assumed that sodium alginate interacted with lactose molecules in SD particles. The drug release from the matrix tablet prepared with the SD particles and acetaminophen in JPXIII No. 1 medium (pH 1.2) was more prolonged than that of a physically mixed tablet of lactose, sodium alginate and the drug, because of the improved gel forming property of sodium alginate formulated in the SD particles. (C) 1998 Elsevier Science B.V. All rights reserved.