Poor solubility of drug compounds is a great issue in drug industry today and decreasing particle size is one efficient and simple way to overcome this challenge. Drug nanocrystals are solid nanosized drug particles, which are covered by a stabilizer layer. In nanoscale many physical properties, like compound solubility, are different from the solubility of bulk material, and due to this drug nanocrystals can reach supersaturation as compared to thermodynamic solubility. The most important effect of the smaller particle size is that dissolution rate is highly enhanced mainly due to the increased surface area. In this review the most important properties of nano crystalline drug compounds are presented, with multiple examples of the development and characterization of nanocrystalline drug formulations.
Nanosizing is simple and straightforward way to improve solubility properties of poorly soluble drug materials, and often even very small changes in particle size are enough for acceptable product performance. The most important property of drug nanocrystal is increased dissolution rate due to the smaller particle size, but in nanoscale physical properties like solubility are also different from thermodynamic solubility value. These two important properties of drug nanocrystals can be utilized in order to reach higher bioavailability with nanocrystal formulations, and drug nanocrystals are one versatile option for improving solubility properties of BCS class II and in some cases also class IV drugs. There are already a lot of studies and marketed products with different formulations in various administration routes based on drug nanocrystals. In the future the research will be headed more on functional properties of the stabilizers utilized in drug nanocrystals, role of supersaturation and QbD approach in formulation design, and drug targeting applications for example in cancer therapeutics or theranostics through the attachment of protecting layers and targeting ligands on the surfaces of the nanosystems.
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