NMR diffusion coefficient study of steroid–cyclodextrin inclusion complexes

Cameron, Kenneth S.; Fielding, Lee A.

doi:10.1002/mrc.1083

Cited by 54 publications

(35 citation statements)

References 9 publications

(7 reference statements)

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“…The densities and particle sizes were taken to be those of a typical solid particulate material. Drug molecular weight was assumed to be 350 g/mol, and diffusivity was assumed to be 5.0EÀ6 cm 2 /s, a typical value for a small molecular weight drug molecule (Cameron and Fielding, 2002;Carrier et al, 2007). The properties of CD were taken to be those of b-CD (Cameron and Fielding, 2002); molecular weight and solubility were obtained from SciFinder 1 .…”

Section: Numerical Solution To the Ncpm Model Equationsmentioning

confidence: 99%

“…Drug molecular weight was assumed to be 350 g/mol, and diffusivity was assumed to be 5.0EÀ6 cm 2 /s, a typical value for a small molecular weight drug molecule (Cameron and Fielding, 2002;Carrier et al, 2007). The properties of CD were taken to be those of b-CD (Cameron and Fielding, 2002); molecular weight and solubility were obtained from SciFinder 1 . Other input parameters were assigned representative ''low'' and ''high'' values, including drug solubility, absorption constant, dose, binding constant, molar ratio of CD:drug; and the volume of the intestinal lumen.…”

Section: Numerical Solution To the Ncpm Model Equationsmentioning

confidence: 99%

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Modeling the influence of cyclodextrins on oral absorption of low‐solubility drugs: I. Model development

Gamsiz

Miller

Thombre

et al. 2009

Biotech & Bioengineering

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The ability to quantitatively predict the influence of a solubilization technology on oral absorption would be highly beneficial in rational selection of drug delivery technology and formulation design. Cyclodextrins (CDs) are cyclic oligosaccharides which form inclusion complexes with a large variety of compounds including drugs. There are many studies in the literature showing that complexation between CD and drug enhances oral bioavailability and some demonstrating failure of CD in bioavailability enhancement, but relatively little guidance regarding when CD can be used to enhance bioavailability. A model was developed based upon mass transport expressions for drug dissolution and absorption and a pseudo-equilibrium assumption for the complexation reaction with CD. The model considers neutral compound delivered as a physical mixture with CD in both immediate release (IR) and controlled release (CR) formulations. Simulation results demonstrated that cyclodextrins can enhance, have no effect, or hurt drug absorption when delivered as a physical mixture with drug. The predicted influence depends on interacting parameter values, including solubility, drug absorption constant, binding constant, CD:drug molar ratio, dose, and assumed volume of the intestinal lumen. In general, the predicted positive influence of dosing as a physical mixture with CD was minimal, alluding to the significance of dosing as a preformed complex. The model developed enabled examination of which physical and chemical properties result in oral absorption enhancement for neutral drug administered as a physical mixture with CD, demonstrating the utility of modeling the influence of a drug delivery agent (e.g., CD) on absorption for rational dosage form design.

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Section: Numerical Solution To the Ncpm Model Equationsmentioning

confidence: 99%

Section: Numerical Solution To the Ncpm Model Equationsmentioning

confidence: 99%

Modeling the influence of cyclodextrins on oral absorption of low‐solubility drugs: I. Model development

Gamsiz

Miller

Thombre

et al. 2009

Biotech & Bioengineering

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“…Changes in relaxation times have also been measured [128,129], but the interpretation of the data is model dependent and less straightforward than data from self-diffusion measurements, which are conceptually easier and often nowadays experimentally easy to obtain. NMR diffusometry has been used to study inclusion complexes between cyclodextrin and different substrates [130][131][132][133]. The selfdiffusion measurements are in principle applicable to any systems as long as the free and complexed guests (please note that on account of the rapid exchange on the NMR time scale, average diffusion coefficients for both the guest and for the CD are obtained)…”

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confidence: 99%

The formation of host–guest complexes between surfactants and cyclodextrins

Valente

Söderman

2014

Advances in Colloid and Interface Science

181

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Cyclodextrins are able to act as host molecules in supramolecular chemistry with applications ranging from pharmaceutics to detergency. Among guest molecules surfactants play an important role with both fundamental and practical applications. The formation of cyclodextrin/surfactant host-guest compounds leads to an increase in the critical micelle concentration and in the solubility of surfactants. The possibility of changing the balance between several intermolecular forces, and thus allowing the study of, e.g., dehydration and steric hindrance effects upon association, makes surfactants ideal guest molecules for fundamental studies. Therefore, these systems allow for obtaining a deep insight into the host-guest association mechanism. In this paper, we review the influence on the thermodynamic properties of CD-surfactant association by highlighting the effect of different surfactant architectures (single tail, double-tailed, gemini and bolaform), with special emphasis on cationic surfactants. This is complemented with an assessment of the most common analytical techniques used to follow the association process. The applied methods for computation of the association stoichiometry and stability constants are also reviewed and discussed; this is an important point since there are significant discrepancies and scattered data for similar systems in the literature.In general, the surfactant-cyclodextrin association is treated without reference to the kinetics of the process. However, there are several examples where the kinetics of the process can be investigated, in particular those where volumes of the CD cavity and surfactant (either the tail or in special cases the head group) are similar in magnitude.This will also be critically reviewed.

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“…[14] Receptor 4 was named dalexabe because this compound is made up of [ [17,18] in the presence of a molecule with similar size, daxacyan (which is well-known to not form a dimer), [15] confirmed that in diluted solutions receptor 4 stands as a monomer, as the diffusion coefficients differed by less than 10 %.…”

Section: Resultsmentioning

confidence: 94%

A Highly Enantioselective Receptor for Carbamoyl Lactic Acid

Muñiz¹,

Simón²,

Alcázar

et al. 2009

Eur J Org Chem

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A new receptor based on a 9,9‐dimethylxanthene framework was synthesized. Owing to its suitable oxyanion hole structure, this receptor is able to associate carboxylic acids and anions. The introduction of a chiral center provides enantioselective properties to this receptor as a result of its different interactions with both enantiomers of the substrate. The combination of this skeleton with a fluorescent unit such as dansyl allows the detection of small amounts of carboxylic acids by making use of fluorescent techniques.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

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NMR diffusion coefficient study of steroid–cyclodextrin inclusion complexes

Cited by 54 publications

References 9 publications

Modeling the influence of cyclodextrins on oral absorption of low‐solubility drugs: I. Model development

Modeling the influence of cyclodextrins on oral absorption of low‐solubility drugs: I. Model development

The formation of host–guest complexes between surfactants and cyclodextrins

A Highly Enantioselective Receptor for Carbamoyl Lactic Acid

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