Chem. Pharm. Bull. 53(1) 37—41 (2005)

polyvinylpyrrolidone (PVP) can markedly enhance the dissolution of poorly water-soluble drugs. The mechanism responsible for such enhanced dissolution has been the subject of debate. Some authors have proposed that the increased drug dissolution rate is due to the formation of a high-energy amorphous drug phase. Several water-soluble polymer carrier systems, such as polyethylene glycol (PEG), PVP, and hydroxypropylcellulose (HPC), have been used in fast-release preparations. The interaction mechanisms between the drug and the carrier in solid dispersions have been studied. Previous studies of naproxen-a-lactose monohydrate solid dispersions, prepared using melting methods, supported the existence of a high-energy amorphous drug phase in systems containing more than 50% a-lactose monohydrate. The dissolution data suggested that the dissolution rate of this phase was 7—20-fold greater than the crystalline drug. Recently, a spray-drying technique has yielded an amorphous form of such crystalline drugs as cimeditine that becomes amorphous when spray-dried with chitosan, as reported by He et al. This indicates that a solid dispersion was formed when cimeditine was dispersed in the chitosan molecules by spray drying. Corrigan et al. tried to make an amorphous drug by spray drying using PVP as a carrier. Generally, the dissolution rate of a drug increases when a solid dispersion is formed using a polymer as a carrier, as described above. However, only a few studies have investigated the slow release of a drug after the formation of a solid dispersion using spray-drying. Shaikh et al. performed spraydrying using acetaminophen (Act) and ethylcellulose (EC) and tried to achieve a sustained release of Act. Their results demonstrated that it is possible to form a solid dispersion by dispersing Act using a spray-drying technique with EC molecules in a molecular state. They concluded that the sustained release of Act from this solid dispersion was caused by an increase in the viscosity of EC. In this study, we designed matrix particles to slowly release Act by changing the mixture ratio of chitosan and Act. Slow release in the digestive tract is attempted in this formation by using chitosan powder (Cht) as a carrier and the solid dispersion in Cht and between drugs. As expected, the absorbability of the drug from the mucosa increased, because Cht easily harmonizes with biological membrane. In addition, the dosage form design of the administration to the lung is also possible, because fine particles are prepared by a spray-drying technique. Then, the design of the particles for the slow release of the drug was tried by forming a solid dispersion by a spray-drying technique that used chitosan as the carrier.