Potential interaction between zinc ions and a cyclodextrin-based diclofenac formulation

Complexes of diclofenac sodium (DF-Na) with hydroxypropyl betacyclodextrin (HPβCD) were prepared by co-evaporation in a 1:1 ratio and characterized in light of previously reported data. Phase solubility diagrams were obtained for DF-Na with HPβCD in the presence and absence of zinc ions. Dissolution profiles were obtained for DF-Na and its HPβCD complex at acidic (pH 1.2) as well as in phosphate buffer (pH 6.8), in the presence and absence of zinc. HPβCD, as expected, was shown to improve the dissolution of DF-Na in acidic medium but not in phosphate buffer (pH 6.8). The presence of zinc ions decreased the in vitro dissolution of DF-HPβCD complex in acidic medium (pH 1.2) but not in phosphate buffer (pH 6.8). It was confirmed that the precipitate that was formed by zinc ions in the presence of HPβCD and DF-Na contained no cyclodextrin and most likely it was a mixture of the complexes: DF2-Zn and DF-Zn with some molecules of water. In vivo experiments on rats have shown that HPβCD has no statistically significant effect on absorption or bioavailability of DF-Na in spite of the observed improvement of its in vitro dissolution by HPβCD. Moreover, zinc ions were shown to decrease the absorption rate of DF-Na in rats model but did neither significantly alter the absorption nor bioavailability of DF-HPβCD complex. The zinc induced precipitates of DF were shown to have significantly different crystalline properties when HPβCD was present. Therefore, the pharmaceutical details of a DF-Na preparation should be considered when designing the formulation and predicting possible interaction between DF-Na (or other potential NSAIDs) and zinc metal.

Inclusion Complexes of β-Cyclodextrin with Ionic Liquid Surfactants

The three kinds of ionic liquid (IL) surfactants, 1-dodecyl-3-methylimidazolium hexafluorophosphate (C(12)mimPF(6)), 1-tetradecyl-3-methylimidazolium hexafluorophosphate (C(14)mimPF(6)), and 1-hexadecyl-3-methylimidazolium hexafluorophosphate (C(16)mimPF(6)), were used to form the inclusion complexes (ICs) with beta-cyclodextrin (beta-CD). The surface tension measurements revealed that there were two kinds of inclusion formations, 1:1 and 1:2 (beta-CD/IL) stoichiometry for beta-CD-C(12)mimPF(6) and beta-CD-C(14)mimPF(6) ICs, and only 1:1 stoichiometry for beta-CD-C(16)mimPF(6) ICs. These inclusion compounds were further characterized by XRD, (13)C CP/MAS NMR, (1)H NMR, rotating frame nuclear Overhauser effect spectroscopy (ROESY), and thermogravimetry (TGA). The results showed that these ICs were fine crystalline powder. The host-guest system presented a channel-type structure, and each glucose unit of beta-CD was in a similar environment. It was suggested that hydrophobicity played a crucial role in supporting the formation of ICs. The decomposition temperature of these ICs was lower than those of their precursors. Furthermore, the possible inclusion structures were also speculated. These inclusion behaviors are likely to be used to recover ILs in the process of their preparation.

Preparation and Characterization of Inclusion Complexes of β-Cyclodextrin with Ionic Liquid

The solubilities of beta-cyclodextrin (beta-CD), ionic liquid (IL) 1-butyl-3-methylimidazolium hexafluorophosphate (bmimPF6), and their mixture in water were determined, and the conductivity of these aqueous solutions was measured. It was demonstrated that beta-CD and bmimPF6 could enhance the solubility of each other, and the solubility curves of each were linear with gradients of about 1. The conductivity decreased remarkably with increasing beta-CD concentration, and a discernible break in the conductivity curve could be observed when beta-CD and bmimPF6 were equimolar in the solution. The solubility and conductivity results indicated that inclusion complexes (ICs) of 1:1 stoichiometry were formed. The inclusion compounds were further characterized by using powder X-ray diffraction (XRD) analysis, 13C CP/MAS (cross-polarization magic-angle spinning) NMR and 1H NMR spectroscopy, and thermogravimetric analysis (TGA). The results showed that the ICs were a fine crystalline powder. The host-guest system exhibited a channel-type structure and each glucose unit of beta-CD was in a similar environment. The decomposition temperature of the ICs was lower than that of bmimPF6 and beta-CD individually.

A Raman spectroscopic study of the diclofenac sodium–β-cyclodextrin interaction

The inclusion complex of diclofenac sodium (DCFNa) and beta-cyclodextrin (betaCD) was prepared and analyzed by using Raman and SERS spectroscopy. The interaction between DCFNa and betaCD molecules was evidenced by monitoring the change in the peak positions and the widths of some guest molecule bands relative to those observed in the spectra of the free compound and 1:1 DCFNa-betaCD physical mixture. Raman data have shown that the interaction between the guest and host molecules in the 1:1 DCFNa-betaCD complex is maintained both through the dichlorophenyl ring and the phenylacetate group. SER spectra revealed that depending on the pH value of the solution different isomeric forms of the 1:1 guest-host complex are preferentially adsorbed on the silver surface via the nonbonding electrons of the oxygen atom. The orientation of the adsorbed species with respect to the metal surface was also elucidated.

Cyclodextrin complexes of salts of acidic drugs. Thermodynamic properties, structural features, and pharmaceutical applications

The objective of this mini-review is to summarize the findings concerning the physicochemical properties and the pharmaceutical applications of acidic drugs whose performances have been modified by simultaneous complexation with cyclodextrins and salt formation. Particular attention is paid to the approaches undertaken for increasing the solubility of the drugs by proper choice of the type of counterion analogously to what has been reported for complexes of basic drugs in the presence of hydroxy acids.

Evidence of the Existence of 2:1 Guest–Host Complexes between Diclofenac and Cyclodextrins in D2O Solutions. A 1H and 13C NMR Study on Diclofenac/β-Cyclodextrin and Diclofenac/2-Hydroxypropyl-β-cyclodextrin Systems

The interaction of diclofenac sodium salt (DCFNa) and two cyclodextrins, β-cyclodextrin (βCD) and 2-hydroxypropyl-β-cyclodextrin (HPβCD), studied in D2O solution with different NMR techniques (1H, 13C NMR, ROESY experiments, NMR titrations), shows the existence of multiple equilibria involving 1:1 and 2:1 guest–host complexes.

FT-IR and X-ray spectroscopic investigations of Na-diclofenac-cyclodextrins interactions

The association of DCF-Na (the salt of the 2-[(2,6-dichlorophenyl)amino]-phenyl-acetic acid) with beta-CD (cyclodextrin) in some therapeutic formulas can contribute to the optimisation of the physico-chemical and pharmaceutical properties of the parent drug. The understanding of the interaction between DCF with beta-CD represents the objective of this study. FT-IR spectroscopy is one of the methods which clarify the nature of these interactions in complexes of such type. Therefore the changes in FT-IR spectra of binary dispersed systems DCF/beta-CD in physical mixture and coprecipitate from methanol (molar ratios: 1/1, 1/2, 2/3, 3/4, 7/4) were analysed. The analysis of the broadening of the X-ray powder diffraction line has been applied to investigate the average effective crystallite size, the mean square of the microstrain caused by distortions within beta-CD crystallite and the fault probability in the binary dispersed DCF/beta-CD coprecipitate system.