Monograph: |
BETA CYCLODEXTRINS
Cyclodextrins are cyclic oligosaccharides, composed of glucopyradase units, with a cavity in the centre. Different types of cyclodextrins, namely alpha, beta, gamma, delta and substituted (methylated, hydroxy, oxylated are available. Beta cyclodextrins are most widely used in pharmaceutical industry because of its cavity size, efficiency of drug complexation, availability in pure form and relatively low cost. Cyclodextrins are gaining a bit of importance as excipients in increasing the solubility, dissolution and diffusion of various hydrophobic drugs. For the first time, monographs of cyclodextrins were in the European pharmacopoeia. Currently about seventy drugs contain cyclodextrins and more than half among them contain natural beta-cyclodextrin.
Cyclodextrins are mainly used to increase the aqueous solubility, stability and bioavailability of the drug and they can also be used to convert liquid drugs into microcrystalline powders. It prevent drug-drug or drug-excipient interaction and to reduce drug irritation after oral or topical administration. Beta-cyclodextrin is used in industry for modifying the physico-chemical properties of the drug, stabilizing the volatile materials and flavours, providing protection against oxidation and uv degradation during storage and to increase the solubility of the water insoluble materials. All the above characters of beta-cyclodextrins are because of its ability to form monomolecular inclusion complexes with different drugs.
Inclusion complexes : The structures of cyclodextrins assume a truncated cone or torus shape . The interior of this cavity is hydrophobic, whereas the entrance of the cavity is hydrophilic in nature. The lipophilic cavity of cyclodextrin molecule provides a microenvironment into which an appropriately sized non-polar drug molecule, or more often non-polar moieties of the drug molecule can enter to form inclusion complexes. Among cyclodextrins alpha-cyclodextrin has the smallest cavity , whereas beta and gamma cyclodextrins have larger internal diameters.
The cyclodextrin complexes are known to improve the diffusion, penetration , permeability and bioavailability of the drugs.
Use of cyclodextrin in cosmetic industry : beta-cyclodextrin is utilized in tooth pastes containing triclosan. Triclosan is an antibacterial agent, which is commonly used in tooth-pastes to prevent plaque formation, but the aqueous solubility of triclosan is very low , which is the limiting factor for its availability in oral cavity . The availability of triclosan in enhanced by complex formation with beta-cyclodextrin.
Stability of various drugs at elevated temperatures , higher relative humidities has been improved by complexion with beta-cyclodextrin.
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