Abstract
Cyclodextrins (CDs) are oligosaccharides widely used in the pharmaceutical field. In this review, a detailed examination of the literature of the last two decades has been made to understand the role of CDs in nasal drug delivery systems. In nasal formulations, CDs are used as pharmaceutical excipients, as solubilizers and absorption promoters, and as active ingredients due to their several biological activities (antiviral, antiparasitic, anti-atherosclerotic, and neuroprotective). The use of CDs in nasal formulations allowed obtaining versatile drug delivery systems intended for local and systemic effects, as well as for nose-to-brain transport of drugs. In vitro and in vivo models currently employed are suitable to analyze the effects of CDs in nasal formulations. Therefore, CDs are versatile pharmaceutical materials, and due to the continual synthesis of new CDs derivatives, the research on the new nasal applications is an interesting field evolving in the coming years, to which Italian research will still contribute.
Highlights
Nasal drug delivery can be a good alternative route for the administration of drugs intended for systemic and brain targeting, for drugs with low oral bioavailability due to high hepatic first-pass metabolism and/or a low permeation through the BloodBrain Barrier (BBB)
Nasal formulations obtained in the presence of CDs have been proposed for local therapy, systemic absorption, or brain targeting of the active drugs
The access of drugs in the central nervous system (CNS) after nasal administration is generally allowed by one or more of these three main pathways: (i) in the respiratory region, the drug may be absorbed into the bloodstream from which it can target the brain by crossing the BBB; (ii) in the olfactory region, the drug may directly target the cerebrospinal fluid (CSF) by permeation across the olfactory mucosa, or reach the olfactory bulb by transcellular transport via olfactory neurons; (iii) the drugs penetrating in the respiratory or olfactory mucosa can reach the portions of trigeminal neurons, and they can be transported via trigeminal nerves [24]
Summary
Nasal drug delivery can be a good alternative route for the administration of drugs intended for systemic and brain targeting, for drugs with low oral bioavailability due to high hepatic first-pass metabolism and/or a low permeation through the BloodBrain Barrier (BBB). Inclusion complexes are formed by molecular encapsulation of a drug into the hydrophobic cavity of the CD; this process, due to the formation of non-covalent bonds between the guest (drug) and host (CD), is described by the following reversible reaction showing that guest molecules are in equilibrium with free molecules in the solution:. Β-CD is the most used CD in pharmaceutical products, and it is of easy production and the least expensive between oligosaccharides Because of their very low oral bioavailability, β-CD and the other parent CDs are not toxic after oral administration, as well as most of their derivatives. In addition to the products currently on the market, it is worth mentioning the more recent investigations on nasal and intranasal formulations where the promising role of CDs is focused on their ability to increase drug solubility and permeability through nasal mucosa [20]
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