Irbesartan (IBS),an angiotensin Ⅱ receptor antagonist,is a poorly water-soluble drug.To enhance the dissolution rate,IBS nanocomposite particles were produced via an anti-solvent precipitation combined with a spray drying process.Four pharmaceutically acceptable excipients,including three different polymers and one charged surfactant,were evaluated as stabilizers to control the particle size and to prevent the agglomeration of particles.The experiment results indicated that polyvinylpyrrolidone (PVP) combined with sodium dodecyl sulfate (SDS) significantly decreased the particle size and enhanced the stability of drug nanoparticles.As a result,we finally obtained stable IBS nanoparticles with an average size of approximately 55 nm.In the dissolution test,the IBS nanocomposite particles showed a significantly enhanced dissolution rate and 100％ of the drug dissolved within 20 min.In contrast,the physical mixture with the same recipe as the IBS nanocomposite particles and the raw IBS reached only 8％ and 40％ of drug dissolved in 20 min,respectively,and both of them did not dissolve completely,even after 120 min.