Phase behavior of ketoprofen-poly(lactic acid) drug particles formed by rapid expansion of supercritical solutions.

The present contribution investigates whether it is possible to form stable amorphous particles of ketoprofen-poly(lactic acid), naproxen-poly(lactic acid), and indomethacin-poly(lactic acid). Amorphization and micronization of these poorly water-soluble drugs offer a combined way to improve the solubility and enhance the dissolution rate. The particles were formed by pulsed rapid expansion of supercritical CO(2) solutions and characterized in the aerosol phase with rapid-scan infrared spectroscopy and after collection with scanning electron microscopy and X-ray diffraction. None of the three drug-poly(lactic acid) mixtures showed long-term stability on the order of weeks against the reversion from the amorphous to the crystalline state. Ketoprofen was the only drug that formed mixed amorphous particles with at least short-term stability. The long-term products turned out to be submicrometer- to micrometer-sized particles with a crystalline drug core and an amorphous poly(lactic acid) shell. Moreover, we found that the poly(lactic acid) coating stabilizes the particles against agglomeration.