Controlled precipitation produced aqueous nanoparticle suspensions of a poorly water soluble drug, itraconazole (ITZ), in an amorphous state, despite unusually high potencies (drug weight/total weight) of up to 94%. Adsorption of the amphiphilic stabilizer hydroxypropylmethylcellulose (HPMC) at the particle-aqueous solution interface arrested particle growth, producing surface areas from 13 to 51 m(2)/g. Dissolution of the particles in acidic media yielded high plateau levels in supersaturation up to 90 times the equilibrium solubility. The degree of supersaturation increased with particle curvature, as characterized by the surface area and described qualitatively by the Kelvin equation. A thermodynamic analysis indicated HPMC maintained amorphous ITZ in the solid phase with a fugacity 90 times the crystalline value, while it did not influence the fugacity of ITZ in the aqueous phase. High surface areas led to more rapid and levels of supersaturation higher than those seen for low-surface area solid dispersions, which undergo crystallization during slow dissolution. The rapid generation of high levels of supersaturation with potent amorphous nanoparticles, containing small amounts of stabilizers oriented at the particle surface, offers new opportunities for improving bioavailability of poorly water soluble drugs.