The unexpected increase of clotrimazole apparent solubility using randomly methylated β-cyclodextrin

Effect of temperature and propylene glycol as a cosolvent on dissolution of clotrimazole

Herein, the solubility study of clotrimazole was performed in a propylene glycol+water system. The solubility values were fitted to various cosolvency equations. The model accuracies were studied with the computation of the mean relative deviations. The thermodynamic behavior was investigated according to the van't Hoff and Gibbs equations for clotrimazole in the propylene glycol+water system. Furthermore, the density data for clotrimazole were determined in mixtures of propylene glycol+water and fitted to the Jouyban-Acree equation.

Mucoadhesive Poloxamer-Based Hydrogels for the Release of HP-β-CD-Complexed Dexamethasone in the Treatment of Buccal Diseases

Oral lichen planus (OLP) is an ongoing and chronic inflammatory disease affecting the mucous membrane of the oral cavity. Currently, the treatment of choice consists in the direct application into the buccal cavity of semisolid formulations containing a corticosteroid molecule to decrease inflammatory signs and symptoms. However, this administration route has shown various disadvantages limiting its clinical use and efficacy. Indeed, the frequency of application and the incorrect use of the preparation may lead to a poor efficacy and limit the treatment compliance. Furthermore, the saliva clearance and the mechanical stress present in the buccal cavity also involve a decrease in the mucosal exposure to the drug. In this context, the design of a new pharmaceutical formulation, containing a steroidal anti-inflammatory, mucoadhesive, sprayable and exhibiting a sustained and controlled release seems to be suitable to overcome the main limitations of the existing pharmaceutical dosage forms. The present work reports the formulation, optimization and evaluation of the mucoadhesive and release properties of a poloxamer 407 thermosensitive hydrogel containing a poorly water-soluble corticosteroid, dexamethasone acetate (DMA), threaded into hydroxypropyl-beta-cyclodextrin (HP-β-CD) molecules. Firstly, physicochemical properties were assessed to ensure suitable complexation of DMA into HP-β-CD cavities. Then, rheological properties, in the presence and absence of various mucoadhesive agents, were determined and optimized. The hydration ratio (0.218-0.191), the poloxamer 407 (15-17 wt%) percentage and liquid-cyclodextrin state were optimized as a function of the gelation transition temperature, viscoelastic behavior and dynamic flow viscosity. Deformation and resistance properties were evaluated in the presence of various mucoadhesive compounds, being the sodium alginate and xanthan gum the most suitable to improve adhesion and mucoadhesion properties. Xanthan gum was shown as the best agent prolonging the hydrogel retention time up to 45 min. Furthermore, xanthan gum has been found as a relevant polymer matrix controlling drug release by diffusion and swelling processes in order to achieve therapeutic concentration for prolonged periods of time.

Preparation and Biophysical Characterization of Quercetin Inclusion Complexes with β-Cyclodextrin Derivatives to be Formulated as Possible Nose-to-Brain Quercetin Delivery Systems

Quercetin (Que) is a flavonoid associated with high oxygen radical scavenging activity and potential neuroprotective activity against Alzheimer's disease. Que's oral bioavailability is limited by its low water solubility and extended peripheral metabolism; thus, nasal administration may be a promising alternative to achieve effective Que concentrations in the brain. The formation of Que-2-hydroxypropylated-β-cyclodextrin (Que/HP-β-CD) complexes was previously found to increase the molecule's solubility and stability in aqueous media. Que-methyl-β-cyclodextrin (Que/Me-β-CD) inclusion complexes were prepared, characterized, and compared with the Que/HP-β-CD complex using biophysical and computational methods (phase solubility, fluorescence and NMR spectroscopy, differential scanning calorimetry (DSC), and molecular dynamics simulations (MDS)) as candidates for the preparation of nose-to-brain Que's delivery systems. DSC thermograms, NMR, fluorescence spectroscopy, and MDS confirmed the inclusion complex formation of Que with both CDs. Differences between the two preparations were observed regarding their thermodynamic stability and inclusion mode governing the details of molecular interactions. Que's solubility in aqueous media at pH 1.2 and 4.5 was similar and linearly increased with both CD concentrations. At pH 6.8, Que's solubility was higher and positively deviated from linearity in the presence of HP-β-CD more than with Me-β-CD, possibly revealing the presence of more than one HP-β-CD molecule involved in the complex. Overall, water solubility of lyophilized Que/Me-β-CD and Que/HP-β-CD products was approximately 7-40 times and 14-50 times as high as for pure Que at pH 1.2-6.8. In addition, the proof of concept experiment on ex vivo permeation across rabbit nasal mucosa revealed measurable and similar Que permeability profiles with both CDs and negligible permeation of pure Que. These results are quite encouraging for further ex vivo and in vivo evaluation toward nasal administration and nose-to-brain delivery of Que.

Simple circular dichroism method for selection of the optimal cyclodextrin for drug complexation

Abstract

Cyclodextrins are very important excipients in the pharmaceutical industry. Given the multitude of native and semisynthetic cyclodextrin derivatives, there is a need for a rapid and reliable method for the selection of the optimal cyclodextrins for further pharmaceutical testing. During our research, circular dichroism (CD) spectroscopy has been successfully used to describe the qualitative and quantitative complexation of model compounds with different cyclodextrins. For the appearance of a circular dichroism signal, either a chiral or a chirally perturbed chromophore is required. Achiral or racemic compounds do not have corresponding circular dichroism spectra and neither do chiral cyclodextrins due to the absence of a chromophore group. During complexation of a chromophoric guest molecule, its absorption transition becomes chirally perturbed in the proximity of a cyclodextrin molecule and an induced circular dichroism (ICD) signal appears. This phenomenon gives an inherent selectivity to the method. The sign and intensity of the induced circular dichroism signal in case of different cyclodextrins provides information about the approximate structure of the complex as well as their stability relative to each other. In this study, we report a straightforward induced circular dichroism -based approach for the rapid preselection of the optimal cyclodextrin. The distinctive features of the method were demonstrated using five azole-type antifungal drug molecules (fluconazole, miconazole, clotrimazole, bifonazole and tioconazole) along with native α-, β-, and γ-cyclodextrins, as well as dimethyl-, trimethyl-, carboxymethyl-, hydroxypropyl- and sulfobuthylether-β-cyclodextrins. In addition, with the aid of this method, 27 stability constants were determined, amongst which 16 have been unavailable in the literature previously.

Graphic abstract

Phase solubility studies and anti-Trichomonas vaginalis activity evaluations of metronidazole and methylated β-cyclodextrin complexes: Comparison of CRYSMEB and RAMEB

Metronidazole (MTZ) is a 5-nitroimidazole drug used for the treatment of Trichomonas vaginalis parasitic infection. Aqueous formulations containing MTZ are restricted because apparent solubility in water of this drug is low. In this context, two methylated-β-cyclodextrins (CRYSMEB and RAMEB) were used as a tool to increase apparent solubility of MTZ in water. CRYSMEB was limited by its own solubility in water (15% w/w, 12.59 mM), while RAMEB at a concentration of 40% w/w (300.44 mM) allowed a maximal increase of apparent solubility of MTZ (3.426% w/w, 200.19 mM). From our knowledge, this corresponds to the highest enhancement of MTZ apparent aqueous solubility ever reported in the literature using methylated cyclodextrins. In vitro evaluations showed that anti-T. vaginalis activity of MTZ formulated with CRYSMEB and RAMEB was preserved.

Strategies for Prevention and Treatment of Trichomonas vaginalis Infections

The last estimated annual incidence of Trichomonas vaginalis worldwide exceeds that of chlamydia and gonorrhea combined. This critical review updates the state of the art on advances in T. vaginalis diagnostics and strategies for treatment and prevention of trichomoniasis. In particular, new data on treatment outcomes for topical administration of formulations are reviewed and discussed.

Formulation development and systematic optimization of stabilized ziprasidone hydrochloride capsules devoid of any food effect

CONTEXT AND OBJECTIVE

The objective of the study was to develop a stable capsule formulation of ziprasidone hydrochloride which can be administered without regards to food intake.

MATERIALS AND METHODS

The unstable anhydrous form of ziprasidone hydrochloride was stabilized employing hot-melt extrusion and further optimized by 3² central composite design. The formulation was optimized after establishing acceptable ranges for response variables like disintegration time, dissolution and impurity profile. A crossover fasted and fed in vivo study was conducted in human volunteers to assess the food-effect of optimized formulation vis-à-vis the marketed brand.

RESULTS AND DISCUSSION

The optimized formulation met in-house specifications for various response variables. Further, high values of correlation coefficient vouch the adequate selection of experimental design and its high prognostic ability. In our study, no significant difference was observed between the C_max and AUC values after administration of the optimized formulation in fasted and fed states. On the contrary, there was a statistically significant increase in the C_max and AUC values after oral administration of Zeldox in fed state in comparison to fasted state.

CONCLUSIONS

The present study describes the successful development of a stable formulation of 20 mg of ziprasidone devoid of any food-effects.