A considerable interest in the development of novel drug delivery systems using nanoparticles is emerging in recent years. Nanoparticles represent a promising drug delivery system of controlled and targeted release. Though a number of formulation approaches like micronisation, solubilization using cosolvents, precipitation techniques etc., are used to overcome low solubility and bioavailability issues, still these techniques possess their own limitations. Nanosuspension technology offers novel solution for these poorly soluble drugs by offering plenty of advantages like improved efficacy, reduced toxicity, increased solubility and bioavailability, enhanced biodistribution and improved patient compliance. Nanosuspension is defined as a biphasic system consisting of poorly water soluble drug particles dispersed in a aqueous vehicle in which the diameter of the suspended particle is less than 1?m in size. Nanosuspension enhances the solubility and bioavailability,improves the physical and chemical stability of drugs, and provides a passive drug targeting. It is suitable for hydrophilic drugs, higher drug loading capacity can be achieved with a reduction in dose. The principle techniques used in recent years for preparing nanosuspensions can be classified into four basic methods: (a) wet milling, (b) homogenization, (c) emulsification-solvent evaporation and (d) supercritical fluid method. Wet milling method uses high- shear media mills or pearl mills. Homogenization involves forcing of the suspension under pressure through a valve having a narrow aperture. Emulsification-solvent evaporation technique involves preparing a solution of drug followed by its emulsification in another liquid that is a non-solvent for the drug. Evaporation of the solvent leads to precipitation of the drug. Super critical fluid technology involves expansion of the drug solution in supercritical fluid through a nozzle, which leads to loss of solvent power of the supercritical fluid resulting in precipitation of the drug as fine particles. Newer technique called nanojet technology uses a chamber where a stream of suspension is divided into two or more parts, which colloid with each other at high pressure. The high shear force produced during the process results in particle size reduction.

PHARMACEUTICAL APPLICATION: Nanosuspension showed a promising way of improving drug delivery in pulmonary (eg. Budesonide) and ocular route (eg. Cloricromene). In azithromycin oral nanosuspensions, more than 65% drug was found to get dissolved in 5 hours as compared with 20% of micronized drugs. Ketoprofen nanosuspension was successfully incorporated into pellets for the sustained release of drug over the period of 24 hours. Paclitaxel nanosuspension administered parenterally showed superiority in reducing the median tumor burden. Clofazimine nanosuspension showed an improvement in stability as well as efficacy above the liposomal clofazimine in Mycobacterium avium-infected female mice. In targeted drug delivery, these can be used for targeting antifungal, antimycobacterial, or antileishmanial drugs to macrophages, eg. aphidicolin nanosuspension. Oral administration of the gonadotrophin inhibitor Danazol as a nanosuspension showed increase absolute bioavailability compared to the conventional dispersion. Nanosuspensions greatly increases oral absorption of drugs like Amphotericin B. Also improves bioavailability of poorly soluble drugs like oleanolic acid, a hepatoprotective agent. Examples of marketed nanosuspension: Rapamune by Wyeth, Emend by Merck used as immune-suppressant and anti-emetic respectively.

Thus nanosuspension not only solves the problems of poor solubility and bioavailability but also alters the pharmacokinetics of drug and thus improves drug safety and efficacy.this technology confer a series of special characteristics to the drugs, such as the enhanced dissolution rate and saturation solubility and has obtained great success in the preparation of insoluble drugs.

Dinesh Choudhary

Final Year B.Pharm.

Tags: MET Institute of Pharmacy