ABSTRACT
The bioavailability of solid drugs and the efficacy of their delivery systems are often constrained by size, morphology, and size distribution, since these factors decide the solubilities of the drugs in the aqueous media of our body fluid systems. The lower the particle size of these solid drugs, the higher their dissolution rates and their bioavailability in the body fluids. Micronized drugs with uniform size and morphology are functionally most effective for controlled delivery to the target organs such as heart, lung, tissues, and bones. The pharmaceutical industry today needs a promising method of producing micronized drugs with a narrow size distribution for utilizing the new drug delivery routes, such as dry powder inhalers, needle-free injections, and controlledrelease devices. Like micronization, two other processes, microimpregnation and microencapsulation of the drugs, are also adopted for improvement of functional and aesthetic values. There is great potential for utilizing supercritical carbon dioxide (scCO2) as the medium in all these processes, because the pharmaceutical compounds are thermally labile and the micronized drugs should be free from any organic solvent residues and artifacts. Investigators consider scCO2 to be an attractive solvent or antisolvent in these processes owing to the tunability of its solvent power with small variations in pressure and temperature and to its excellent transport properties (e.g., viscosity and diffusivity); in addition, scCO2 in nontoxic, nonflammable, and environmentally benign.
