Bottom-up approaches for preparing drug nanocrystals: formulations and factors affecting particle size.

The solubility dependent bioavailability problem has become a major hurdle in drug development processes. Drug nanocrystals have been widely accepted by the pharmaceutical industry to improve the bioavailability of poorly water-soluble compounds. Top-down and bottom-up technologies are the two primary technical approaches of drug nanocrystal production. Though the top-down approach has been hugely successful on the commercial front, it has some inherent drawbacks that necessitate the emergence of alternate approaches. The bottom-up approach has not yet been established as a successful commercial technology. However, it has the potential to produce small size drug nanocrystals with less energy demanding processes. The bottom-up approach is commonly known as precipitation technique. It would be possible to stabilize particles at an early stage of precipitation and to generate drug nanocrystals. In the first part of this review article, we have discussed various bottom-up technologies that are currently in use. This has been followed by description and analysis of various process parameters that can affect the final particle size of the drug nanocrystals.