Nanocrystals for controlled delivery: state of the art and approved drug products

INTRODUCTION: Controlled/extended-release formulations offer numerous benefits over conventional especially reduced side effects, improved therapeutic outcomes, and high patient compliance. Controlled release nanocrystal is extremely versatile technology with several advantages such as very high drug loading, ease of manufacturing, avoidance of dose dumping, reproducible drug release. Usually, nanonization of drug is performed to improve dissolution rate, intrinsic solubility, and thereby bioavailability. Most of the times, this is done for immediate release dosage forms where objective is quick onset of action. However, nanocrystals can also provide a sustained, reproducible plasma concentration profile for weeks to months based on tissue microenvironment, surface coating and administration route. AREAS COVERED: This review briefly describes the methods for producing nanocrystals, summarizes preclinical research and commercial products demonstrating tremendous potential of controlled release nanocrystals. EXPERT OPINION: Lipophilic drugs are attractive candidates for the development of nanocrystal based controlled release formulations. However, constraint should be practiced while generalizing the technology for the controlled release purpose. Not all drugs fit in the requirement from the perspectives of physicochemical properties or pharmacokinetics. Additionally, technologies should be explored which can convert the nanocrystal into its final dosage form for administration yet preserves the benefits of small particle size and controlled release.