Spontaneously Forming Nanoemulsions or Self-nanoemulsifying Drug Delivery Systems for Oral Drug Delivery
The oral route is the most convenient and preferred route of drug delivery as it offers a high degree of patient compliance. However, 50% of drugs delivered via the oral route have limited therapeutic efficacy owing to poor water solubility.[33] Furthermore, a majority of the new chemical entities being generated through drug discovery programs also exhibit poor water solubility. The problems associated with such drugs include poor oral bioavailability, erratic absorption profile, high intra- and inter-subject variability and lack of dose proportionality.[34] Furthermore, drug candidates with high water solubility and poor permeability, such as atenolol and metformin (belonging to BCS class III), also exhibit low oral bioavailability and ultimately low therapeutic efficacy. Similarly, most of the therapeutic peptides, such as insulin and calcitonin, are difficult to deliver via the oral route owing to their extreme hydrophilicity, poor permeability and instability in the gastrointestinal (GI) environment. Conventional techniques, such as salt formation, micronization and solubilization using cosolvents, use of permeation enhancers,[35] oily solutions and surfactant dispersions,[36] that were previously employed to increase the oral bioavailability have shown limited utility. Although recently developed strategies, such as solid dispersion technology[37] and inclusion complexes employing cyclodextrins,[38] exhibit good potential, they are successful in some instances and are specific to drug candidates.
The ability of nanosized emulsions or submicronic emulsions to improve the GI absorption of hydrophobic drugs was demonstrated almost three decades ago.[39] However, the use of submicronic emulsions or nanoemulsions in oral delivery was limited owing to disadvantages such as poor palatability due to their lipidic composition. Furthermore, nanoemulsions would have to be consumed in a higher volume to achieve the necessary therapeutic concentration of drugs, for example carbamazepine and quercetin, which have limited solubility in all the oils with pharmaceutical acceptability. This may severely limit patient compliance. Nanoemulsions with high water content cannot be delivered through soft gelatin, hard gelatin or hydroxypropylmethylcellulose capsules for oral delivery. The water content of nanoemulsions may promote hydrolysis and/or precipitation of certain drugs on long-term storage, which could affect their utility in oral delivery. The advent of the spontaneous nanoemulsification approach has reinstated the interest of drug delivery scientist for exploring applications of nanoemulsions for oral drug delivery.
Nanomedicine. 2010;5(10) © 2010 Future Medicine Ltd.
Cite this: Self-nanoemulsifying Drug Delivery Systems: Formulation Insights, Applications and Advances - Medscape - Dec 01, 2010.
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