SOLUBILIZATION OF DRUGS BY USING CYCLODEXTRINS01

SOLUBILIZATION OF DRUGS BY USING CYCLODEXTRINS : 

SOLUBILIZATION OF DRUGS BY USING CYCLODEXTRINS Submitted to ANU as a part of 1st M.pharm , 1st semester curriculum . by I.VENKATESWARLU (M.pharm ) REG NO:Y10MPH08017 Department of pharmaceutics A S N Pharmacy college, Tenali . submitted to Mr. G.V. RAMI REDDY. M.pharm (Ph.D) Department of pharmaceutics A S N Pharmacy college, Tenali.

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Cyclodextrins: Definition:- cyclodextrins are enzymatically modified starches made up of sugar molecules bound together in a ring (cyclic oligosaccharides ). A.S.N

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α -cyclodextrin : six membered sugar ring molecule β -cyclodextrin : seven membered sugar ring molecule γ -cyclodextrin : eight membered sugar ring molecule Among the above three, the mostly used one is β –cyclodextrin because the ring in β –cyclodextrin is correct size for majority of Drug molecules. A.S.N

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Methylated β –cyclodextrins are mostly commenly used, because it is having.., High activity Low toxicity A.S.N

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Description: Outer surface Hydrophilic Polar Inner surface Hydrophobic Less polar Drugs Hydrophobic Can fit into ring Owing to presence of – CH 2 –group Soluble Inclusion complexes Solubility Dissolution Bioavailability A.S.N

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Effect On Drug Bioavailability: CDs enhance the bioavailability of insoluble drugs by ing the.., drug solubility, dissolution , drug permeability. CDs increase the permeability of insoluble hydrophobic drugs, by making the drug available at the surface of the biological barrier. e.g.: skin, mucosa and the eye cornea. from where it partitions into the membrane without disrupting the lipid layers of the barrier . In such cases it is important to use just enough CD to solubilize the drug in the aqueous vehicle since excess may decrease the drug bioavailability . A.S.N

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D r u g   +   C D   ⇌   D r u g :   C D   C o m p l e x Modification of Drug structure by using Cyclodextrins: Cyclodextrins alter the drug structure to.., Aqueous solubility Improving its partition characteristics by.., Altering substituent groups, Using different Salt forms. A.S.N Mode of penetration enhancement by CDs

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Study of CD Complexation: The most widely used approach to study inclusion complexation (Figure) is the phase solubility method described by Higuchi and Connors. Phase solubility diagrams are categorized into A and B types. A type curves indicate the formation of soluble inclusion complexes . B type suggest the formation of inclusion complexes with poor solubility. A B S type response denotes complexes of limited solubility and a B I curve indicates insoluble complexes.

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β-CD often gives rise to B-type curves due to their poor water solubility . The chemically modified CDs like HP-β-CD (Hydroxypropyl-β - CD) and SBE-β-CD (Sulfobutylether-β - CD) usually produce soluble complexes and thus give A-type systems. A P (positively deviating isotherms) A A L (linear increases of drug solubility as a function of CD concentration) A N (negatively deviating isotherms)

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Advantages and disadvantages of cyclodextrins: Advantages: Cyclodextrins can increase the chemical stability of API (compared to other solubilized approaches) by protecting chemically labile regions. Certain cyclodextrins have a high aqueous solubility (>40%) and low viscosity so poorly soluble drug is satisfactory. Disadvantages: If a compound does not dissociate rapidly, the pharmacokinetics of the poorly soluble compound may be altered as release is not immediate Some of cyclodextrins cause to nephrotoxicity administered by parental route.

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REFERENCES: Aulton’s pharmaceutics the design and manufacture of medicines, Michael. E.Aulton.. Page no _ 292,366,560. Physical pharmacy, fourth edition, Alfred Martin. Page no-259, 260, 259. http://www.aapspharmscitech.org/view.asp?art=pt060243 . http://en.wikipedia.org/wiki/Cyclodextrin . http://media.wiley.com/product_data/excerpt/03/35273128/3527312803.pdf .