Improvement in solubility and dissolution rate of 1, 2-dithiole-3-thiones upon complexation with beta-cyclodextrin and its hydroxypropyl and sulfobutyl ether-7 derivatives

Solubilization of drugs using beta-cyclodextrin: Experimental data and modeling

Many drug candidates fail to complete the entire drug development process because of poor physicochemical properties. Solubility is an important physicochemical property which plays a vital role in various stages of drug discovery and development. Several methods have been proposed to enhance the solubility of drugs, and complex formation with cyclodextrins is among them. Beta-cyclodextrin (βCD) is a common excipient for solubilization of drugs. The aim of this study is to develop the mechanistic QSPR models to predict the solubility enhancement of a drug in the presence of βCD. In this study, the solubility enhancement of some drugs in the presence of 10mM βCD at 25°C was experimentally determined or collected from the literature. Two different models to predict the solubilization by βCD were developed by binary logistic regression using structural properties of drugs with more than 80% accuracy. Polar surface area and excess molar refraction are the main parameters for estimating solubilization by βCD. Moreover, other descriptors related to hydrophobicity and the capability of hydrogen bonding formation of molecules could improve the accuracy of the established models.

Improvement of the Ocular Bioavailability of Econazole Nitrate upon Complexation with Cyclodextrins

Econazole nitrate (EC) is an active, imidazole antifungal agent. However, low aqueous solubility and dissolution rate of EC has discouraged its usage for the treatment of ophthalmic fungal infection. In this study, inclusion complexes of EC with cyclodextrins were prepared to enhance its solubility, dissolution, and ocular bioavailability. To achieve this goal, EC was complexed with β-CyD/HP-β-CyD using kneading, co-precipitation, and freeze-drying techniques. Phase-solubility studies were performed to investigate the complexes in the liquid form. Additionally, the complexes in the solid form were characterized with Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), powder X-ray diffraction (PXRD), and transmission electron microscopy (TEM). Furthermore, different eye drops containing EC-CyD complexes were prepared using different polymers and then characterized regarding their drug contents, pH, viscosity, mucoadhesive strength, and in vitro release characteristics. The results showed that stable EC-CyD complexes were formed in 1:1 molar ratio as designated by B_S-type diagram. Econazole nitrate water solubility was significantly increased in about three- and fourfold for β-CyD and HP-β-CyD, respectively. The results showed that the prepared complexes were spherical in shape having an average particle diameter from 110 to 288.33 nm with entrapment efficiency ranging from 64.24 to 95.27%. DSC investigations showed the formation of real inclusion complexes obtained with co-precipitation technique. From the in vitro studies, all eye drops containing co-precipitate complexes exhibited higher release rate than that of other complexes and followed the diffusion-controlled mechanism. In vivo study proved that eye drops containing EC-CyD complexes showed higher ocular bioavailability than EC alone which indicated by higher AUC, C_max, and relative bioavailability values.

Effects of the Preparation Method on the Formation of True Nimodipine SBE-β-CD/HP-β-CD Inclusion Complexes and Their Dissolution Rates Enhancement

The aims of this study were to enhance the solubility and dissolution rate of nimodipine (ND) by preparing the inclusion complexes of ND with sulfobutylether-b-cyclodextrin (SBE-β-CD) and 2-hydroxypropyl-b-cyclodextrin (HP-β-CD) and to study the effect of the preparation method on the in vitro dissolution profile in different media (0.1 N HCl pH 1.2, phosphate buffer pH 7.4, and distilled water). Thus, the inclusion complexes were prepared by kneading, coprecipitation, and freeze-drying methods. Phase solubility studies were conducted to characterize the complexes in the liquid state. The inclusion complexes in the solid state were investigated with differential scanning calorimetry (DSC), X-ray diffractometry (X-RD), and Fourier transform infrared spectroscopy (FT-IR). Stable complexes of ND/SBE-β-CD and ND/HP-β-CD were formed in distilled water in a 1:1 stoichiometric inclusion complex as indicated by an AL-type diagram. The apparent stability constants (Ks) were 1334.4 and 464.1 M(-1) for ND/SBE-β-CD and ND/HP-β-CD, respectively. The water-solubility of ND was significantly increased in an average of 22- and 8-fold for SBE-β-CD and HP-β-CD, respectively. DSC results showed the formation of true inclusion complexes between the drug and both SBE-β-CD and HP-β-CD prepared by the kneading method. In contrast, crystalline drug was detectable in all other products. The dissolution studies showed that all the products exhibited higher dissolution rate than those of the physical mixtures and ND alone, in all mediums. However, the kneading complexes displayed the maximum dissolution rate in comparison with drug and other complexes, confirming the influence of the preparation method on the physicochemical properties of the products.

A novel oral delivery system consisting in "drug-in cyclodextrin-in nanostructured lipid carriers" for poorly water-soluble drug: vinpocetine

The purpose of this study was to develop a new delivery system based on drug cyclodextrin (CD) complexation and loading into nanostructured lipid carriers (NLC) to improve the oral bioavailability of vinpocetine (VP). Three different CDs and three different methods to obtain solid vinpocetine-cyclodextrin-tartaric acid complexes (VP-CD-TA) were contrasted. The co-evaporation vinpocetine-β-cyclodextrin-tartaric acid loaded NLC (VP-β-CD-TA COE-loaded NLC) was obtained by emulsification ultrasonic dispersion method. VP-β-CD-TA COE-loaded NLC was suitably characterized for particle size, polydispersity index, zeta potential, entrapment efficiency and the morphology. The crystallization of drug in VP-CD-TA and NLC was investigated by differential scanning calorimetry (DSC). The in vitro release study was carried out at pH 1.2, pH 6.8 and pH 7.4 medium. New Zealand rabbits were applied to investigate the pharmacokinetic behavior in vivo. The VP-β-CD-TA COE-loaded NLC presented a superior physicochemical property and selected to further study. In the in vitro release study, VP-β-CD-TA COE-loaded NLC exhibited a higher dissolution rate in the pH 6.8 and pH 7.4 medium than VP suspension and VP-NLC. The relative bioavailability of VP-β-CD-TA COE-loaded NLC was 592% compared with VP suspension and 92% higher than VP-NLC. In conclusion, the new formulation significantly improved bioavailability of VP for oral delivery, demonstrated a perspective way for oral delivery of poorly water-soluble drugs.

Pharmacokinetic delivery and metabolizing rate of nicardipine incorporated in hydrophilic and hydrophobic cyclodextrins using two-compartment mathematical model

The dispersion routes of cyclodextrin complexes with nicardipine (NC), such as hydrophilic hydroxypropyl-β-cyclodextrin (NC/HPβCD) and hydrophobic triacetyl-β-cyclodextrin (NC/TAβCD), through the body for controlled drug delivery and sustained release have been examined. The two-compartment pharmacokinetic model described the mechanisms of how the human body handles with ingestion of NC-cyclodextrin complexes in gastrointestinal tract (GI), distribution in plasma, and their metabolism in the liver. The model showed that drug bioavailability was significantly improved after oral administration of cyclodextrin complexes. The mathematical significance of this study to predict nicardipine delivery using pharmacokinetic two-compartment mathematical model with linear ordinary differential equations (ODE) approach represents a valuable tool to emphasize its effectiveness and metabolizing rate and diminish the side effects.

Strategies to address low drug solubility in discovery and development

Drugs with low water solubility are predisposed to low and variable oral bioavailability and, therefore, to variability in clinical response. Despite significant efforts to "design in" acceptable developability properties (including aqueous solubility) during lead optimization, approximately 40% of currently marketed compounds and most current drug development candidates remain poorly water-soluble. The fact that so many drug candidates of this type are advanced into development and clinical assessment is testament to an increasingly sophisticated understanding of the approaches that can be taken to promote apparent solubility in the gastrointestinal tract and to support drug exposure after oral administration. Here we provide a detailed commentary on the major challenges to the progression of a poorly water-soluble lead or development candidate and review the approaches and strategies that can be taken to facilitate compound progression. In particular, we address the fundamental principles that underpin the use of strategies, including pH adjustment and salt-form selection, polymorphs, cocrystals, cosolvents, surfactants, cyclodextrins, particle size reduction, amorphous solid dispersions, and lipid-based formulations. In each case, the theoretical basis for utility is described along with a detailed review of recent advances in the field. The article provides an integrated and contemporary discussion of current approaches to solubility and dissolution enhancement but has been deliberately structured as a series of stand-alone sections to allow also directed access to a specific technology (e.g., solid dispersions, lipid-based formulations, or salt forms) where required.

Preparation and characterization of mosapride citrate inclusion complexes with natural and synthetic cyclodextrins

The aim of this work was to investigate the inclusion complexes between mosapride citrate and SBE7β-CD in comparison with the natural β-CD to enhance its bioavailability by improving the solubility and dissolution rate. The complexation efficiency value of SBE7β-CD was higher than that for β-CD. Solid binary systems of mosapride citrate with CDs were prepared by physical mixing, kneading and freeze-drying techniques at molar ratio of 1:1(drug:CD). Physicochemical characterization of the prepared systems was studied using X-ray diffractometry, differential scanning calorimetry, Fourier-transform infrared spectroscopy and scanning electron microscopy (SEM). Amorphous drug was detectable to large extent in inclusion complexes prepared using the freeze-drying technique. From the dissolution study of different inclusion complexes in simulated saliva solution (pH 6.8), we could concluded that irrespective of the preparation technique, the systems prepared using SBE7β-CD showed better performance than the corresponding ones prepared using β-CD. In addition, the freeze-drying technique showed superior dissolution enhancement than other methods especially when combined with the SBE7β-CD.

An examination of the potential effect of lipids on the first-pass metabolism of the lipophilic drug anethol trithione

In this study, an examination of the potential effect of lipids on the first-pass metabolism of anethol trithione (ATT) was investigated. ATT is metabolized rapidly and extensively in liver into 4-hydroxy-anethole trithione (ATX), which was confirmed using the rat intestinal perfusion with the mesenteric cannulation model. Male Sprague-Dawley rats were orally administered of the lipid-based formulations (prepared by medium chain triglycerides (MCT)), the cyclodextrin formulation and the suspension formulation, respectively. For 6.75 mg/kg groups, ATX/ATT area under the plasma concentration-time curve (AUC) ratio decreased by 87% and 76% after administration of the MCT-based formulations and the cyclodextrin formulation, when compared with the suspension formulation (p < 0.05), respectively; for 2.25 mg/kg groups, it decreased by 53% in the MCT group when compared with the cyclodextrin group (p < 0.05). The saturation of pre-system metabolism of ATT was observed after administration of the MCT-based formulations and the cyclodextrin formulation, likely as a result of enhanced absorption and therefore presentation of higher drug concentrations to liver, when compared with the suspension formulation. A trend toward lower systemic metabolite to parent ratios was evident after administration of the lipid formulations, when compared with the cyclodextrin formulation; however, this was not statistically significant. Further studies on the potential for lipids to inhibit hepatic metabolism are therefore warranted.

Development of machine learning models of β-cyclodextrin and sulfobutylether-β-cyclodextrin complexation free energies

A new set of 142 experimentally determined complexation constants between sulfobutylether-β-cyclodextrin and diverse organic guest molecules, and 78 observations reported in literature, were used for the development of the QSPR models by the two machine learning regression methods - Cubist and Random Forest. Similar models were built for β-cyclodextrin using the 233-compound dataset available in the literature. These results demonstrate that the machine learning regression methods can successfully describe the complex formation between organic molecules and β-cyclodextrin or sulfobutylether-β-cyclodextrin. In particular, the root mean square errors for the test sets predictions by the best models are low, 1.9 and 2.7kJ/mol, respectively. The developed QSPR models can be used to predict the solubilizing effect of cyclodextrins and to help prioritizing experimental work in drug discovery.

Preparation of meloxicam-β-cyclodextrin-polyethylene glycol 6000 ternary system: characterization, in vitro and in vivo bioavailability

Ternary complexes of meloxicam (ML), a poorly water-soluble anti-inflammatory drug, with β-cyclodextrin (βCD) and polyethylene glycol (PEG) 6000 were prepared from an equimolar (ML-βCD) and 10% of PEG. Characterization of the ternary complex was carried out by differential scanning calorimetry and X-ray diffractometry. The solubility of ML increased as a function of increasing the concentration of βCD and PEG 6000. Ternary system increased significantly ML solubility in water. Ternary complexes improved drug release compared with ML and ML-βCD. The oral bioavailability of ML-βCD-PEG was investigated by administration to rat and compared with ML and ML-βCD. The results confirmed that the oral bioavailability of ML was significantly improved by complexation with βCD in the presence of PEG.

Water-soluble organic solubilizers for in vitro drug delivery studies with respiratory epithelial cells: selection based on various toxicity indicators

The aim of this study was to use different toxicity indices to investigate the effect of N, N-Dimethylacetamide (DMA), Polyethylene glycol 400 (PEG 400), Methyl-Pyrrolidone/aromatic hydrocarbon (MPH), Cremophor((R)) EL, and Dimethylsulfoxide (DMSO) on Calu-3 cells. Membrane perturbation and cytotoxicity were investigated using lactate dehydrogenase (LDH), 3-[4, 5-Dimethylthiazol-2-yl]-2, 5-diphenyl tetrazolinium bromide (MTT), transepithelial electrical resistance (TEER) assessment, sodium fluorescein (SF) permeation, and phalloidin actin staining. The MDH activity of cells treated with DMSO (<or= 4.0 v/v), Cremophor EL (<or= 10% v/v), and PEG 400 (<or= 10% v/v) was not significantly altered (p > 0.5). Similarly, DMSO (<or= 8.0% v/v), Cremophor((R)) EL (<or= 16.0% v/v) and PEG 400 (<or= 32.0% v/v) had no significant effect on LDH (p > 0.05). Conversely, MPH and DMA at very low concentrations (<or= 0.25% v/v) induced cell toxicity. However, up to 2.0% v/v MPH and (DMA) had no effect on TEER and SF permeation. No obvious change in actin staining was observed for DMSO (15%), Cremophor((R)) EL (15%), and MPA (1%). However, the actin architecture for cells treated with DMA (1%) and PEG 400 (15%) appeared significantly different from control. Based on this study Cremophor (<or= 10%), PEG 400 (<or= 5%), and DMSO (<or= 5%), and low concentrations of DMA and MPA (<or= 0.25%) were suitable for in vitro studies with Calu-3 cells.

Effect of auxiliary substances on complexation efficiency and intrinsic dissolution rate of gemfibrozil-beta-CD complexes

The studies reported in this work are aimed to elucidate the ternary inclusion complex formation of gemfibrozil (GFZ), a poorly water-soluble drug, with beta-cyclodextrin (beta-CD) with the aid of auxiliary substances like different grades of povidone(s) (viz. PVP K-29/32, PVP K-40, Plasdone S-630, and Polyplasdone XL), organic base (viz. triethanolamine), and metal ion (viz. MgCl(2).6H(2)O), by investigating their interactions in solution and solid state. Phase solubility studies were carried out to evaluate the solubilizing power of beta-cyclodextrin, in association with various auxiliary substances, to determine the apparent stability constant (K (C)) and complexation efficiency (CE) of complexes. Improvement in K (C) values for ternary complexes clearly proves the benefit of the addition of auxiliary substances to promote CE. Of all the approaches used, the use of polymer Plasdone S-630 was found to be the most promising approach in terms of optimum CE and K (C). GFZ-beta-CD (1:1) binary and ternary systems were prepared by kneading and lyophilization methods. The ternary systems clearly signified superiority over binary systems in terms of CE, solubility, K (C), and reduction in the formulation bulk. Optimized ternary system of GFZ-beta-CD-Plasdone S-630 prepared by using lyophilization method indicated a significant improvement in intrinsic dissolution rate when compared with ternary kneaded system. Differential scanning calorimetry, X-ray diffraction, Fourier transform infrared, scanning electron microscopy, and proton nuclear magnetic resonance were carried out to characterize the binary and optimized ternary complex. The results suggested the formation of new solid phases, eliciting strong evidences of ternary inclusion complex formation between GFZ, beta-CD, and Plasdone S-630, particularly for lyophilized products.

Enhancement of oral bioavailability of cilostazol by forming its inclusion complexes

The study was designed to investigate the effect of cyclodextrins (CDs) on the solubility, dissolution rate, and bioavailability of cilostazol by forming inclusion complexes. Natural CDs like beta-CD, gamma-CD, and the hydrophilic beta-CD derivatives, DM-beta-CD and HP-beta-CD, were used to prepare inclusion complexes with cilostazol. Phase solubility study was carried out and the stability constants were calculated assuming a 1:1 stoichiometry. Solid cilostazol complexes were prepared by coprecipitation and kneading methods and compared with physical mixtures of cilostazol and cyclodextrins. Prepared inclusion complexes were characterized by Fourier transform infrared spectroscopy, differential scanning calorimetry (DSC), and X-ray diffraction (XRD) studies. In vitro dissolution study was performed using phosphate buffer pH 6.4, distilled water, and HCl buffer pH 1.2 as dissolution medium. The optimized inclusion complex was studied for its bioavailability in rabbit and the results were compared with those of pure cilostazol and Pletoz-50. Phase solubility study showed dramatic improvement in the solubility of drug by formation of complexes, which was further increased by pH adjustment. The dissolution rate of cilostazol was markedly augmented by the complexation with DM-beta-CD. DSC and XRD curves showed sharp endothermic peaks indicating the reduction in the microcrystallinity of cilostazol. Selected inclusion complex was also stable at ambient temperature up to 6 months. The in vivo study revealed that DM-beta-CD increased the bioavailability of cilostazol with low variability in the absorption. Among all cilostazol-cyclodextrins complexes, cilostazol-DM-beta-CD inclusion complex (1:3) prepared by coprecipitation method showed 1.53-fold and 4.11-fold increase in absorption along with 2.1-fold and 2.97-fold increase in dissolution rate in comparison with Pletoz-50 and pure cilostazol, respectively.

Effect of PVP K30 and/or L-arginine on stability constant of etoricoxib-HPbetaCD inclusion complex: preparation and characterization of etoricoxib-HPbetaCD binary system

The effect of polyvinyl pyrrolidone (PVP) K30 and/or L-arginine on etoricoxib-HPbetaCD complex was investigated. The phase solubility profiles were classified as A(L)-type, both in absence or presence of auxiliary substances used. The apparent stability constant (K(c)) of binary complex obtained at room temperature, 371.80 +/- 2.61 M(-1), was decreased with the addition of PVP and arginine indicating no benefit of addition of auxiliary substances to promote higher complexation efficiency. Therefore, solid etoricoxib-HPbetaCD binary systems were prepared and characterized by proton nuclear magnetic resonance spectroscopy (1HNMR), X-ray powder diffractometry, Fourier transformation-infrared spectroscopy, and dissolution studies. Among all binary systems, a lyophilized product showed superior performance in enhancing dissolution of etoricoxib.

Physicochemical characterization of efavirenz-cyclodextrin inclusion complexes

Efavirenz (EFV) is an oral antihuman immunodeficiency virus type 1 drug with extremely poor aqueous solubility. Thus, its gastrointestinal absorption is limited by the dissolution rate of the drug. The objective of this study was to characterize the inclusion complexes of EFV with beta-cyclodextrin (beta-CD), hydroxypropyl beta-CD (HPbetaCD), and randomly methylated beta-CD (RMbetaCD) to improve the solubility and dissolution of EFV. The inclusion complexation of EFV with cyclodextrins in the liquid state was characterized by phase solubility studies. The solid-state characterization of various EFV and CD systems was performed by X-ray diffraction, differential scanning calorimetry, and scanning electron microscopy analyses. Dissolution studies were carried out in distilled water using US Pharmacopeia dissolution rate testing equipment. Phase solubility studies provided an A(L)-type solubility diagram for beta-CD and A(P)-type solubility diagram for HPbetaCD and RMbetaCD. The phase solubility data enabled calculating stability constants (K (s)) for EFV-betaCD, EFV-HPbetaCD, and EFV-RMbetaCD systems which were 288, 469, and 1,073 M(-1), respectively. The physical and kneaded mixtures of EFV with CDs generally provided higher dissolution of EFV as expected. The dissolution of EFV was substantially higher with HPbetaCD and RMbetaCD inclusion complexes prepared by the freeze drying method. Thus, complexation with HPbetaCD and RMbetaCD could possibly improve the dissolution rate-limited absorption of EFV.

Inclusion complexes of tadalafil with natural and chemically modified beta-cyclodextrins. I: preparation and in-vitro evaluation

The aim of this work was to investigate the inclusion complexation between tadalafil, a practically insoluble selective phosphodiesterase-5 inhibitor (PDE5), and two chemically modified beta-cyclodextrins: hydroxypropyl-beta-cyclodextrin (HP-beta-CD) and heptakis-[2,6-di-O-methyl]-beta-cyclodextrin (DM-beta-CD), in comparison with the natural beta-cyclodextrin (beta-CD) in order to improve the solubility and the dissolution rate of the drug in an attempt to enhance its bioavailability. Inclusion complexation was investigated in both the solution and the solid state. The UV spectral shift method indicated guest-host complex formation between tadalafil and the three cyclodextrins (CDs). The phase solubility profiles with all the used CDs were classified as A(p)-type, indicating the formation of higher order complexes. The complexation efficiency values (CE), which reflect the solubilizing power of the CDs towards the drug, could be arranged in the following order: DM-beta-CD>HP-beta-CD>beta-CD. Solid binary systems of tadalafil with CDs were prepared by kneading and freeze-drying techniques at molar ratios of 1:1, 1:3 and 1:5 (drug to CD). Physical mixtures were prepared in the same molar ratios for comparison. Physicochemical characterization of the prepared systems at molar ratio of 1:5 was studied using differential scanning calorimetry (DSC), X-ray diffractometry (XRD), and Fourier-transform infrared spectroscopy (FTIR). The results showed the formation of true inclusion complexes between the drug and both HP-beta-CD and DM-beta-CD using the freeze-drying method at molar ratio of 1:5. In contrast, crystalline drug was detectable in all other products. The dissolution of tadalafil from all the prepared binary systems was carried out to determine the most appropriate CD type, molar ratio, and preparation technique to prepare inclusion complexes to be used in the development of tablet formulation for oral delivery of tadalafil. The dissolution enhancement was increased on increasing the CD proportion in all the prepared systems. Both the CD type and the preparation technique played an important role in the performance of the system. Irrespective of the preparation technique, the systems prepared using HP-beta-CD and DM-beta-CD yielded better performance than the corresponding ones prepared using beta-CD. In addition, the freeze-drying technique showed superior dissolution enhancement than other methods especially when combined with the beta-CD derivatives.

Influence of sulfobutyl ether beta-cyclodextrin (Captisol) on the dissolution properties of a poorly soluble drug from extrudates prepared by hot-melt extrusion

The aim of this study was to investigate the influence of sulfobutyl ether beta-cyclodextrin (SBE(7)-beta-CD; Captisol on the dissolution properties of a poorly water-soluble drug from extrudates prepared by hot-melt extrusion. Ketoprofen was employed as a model drug. Extrudates containing the parent beta-cyclodextrin (beta-CD) were also produced for comparative evaluation to assess the benefits of SBE(7)-beta-CD. Hot-melt extrudates were produced at 100 degrees C, which was close to the melting point of ketoprofen. The physiochemical properties and the in vitro drug release properties of ketoprofen from extrudates were investigated and compared with samples prepared by physical mixing, co-grinding, freeze-drying and heat-treatment. The solubilizing effects and the interactions of ketoprofen with SBE(7)-beta-CD and beta-CD were investigated using phase solubility and NMR studies, respectively. The dissolution rate of ketoprofen from samples prepared by hot-melt extrusion with SBE(7)-beta-CD was significantly faster than both the physical mixture and the hot-melt extrudates prepared with the parent beta-CD. Moisture absorption studies revealed that the hygroscopic nature of SBE(7)-beta-CD led to particle aggregation and a corresponding decrease in drug release rate for all samples. However, the samples prepared by melt extrusion were least affected by exposure to elevated humidity.

HPLC determination of anethole trithione and its application to pharmacokinetics in rabbits

To evaluate the relative bioavailability of anethole trithione (ATT) from self-microemulsifying drug delivery system (SMEDDS) and tablet, a sensitive, accurate and reliable liquid chromatography method was developed and validated to determine ATT in rabbit plasma. Chromatographic separation was performed on a Diamonsil C18 column by using a mixture of methanol-water (90:10, v/v) delivered at a flow rate of 1.0 ml/min. The wavelength was set at 348 nm and mifepristone was used as the internal standard. A linear relationship for ATT was found in the range of 0.5-32 ng/ml. The mean extraction recoveries of ATT determined over three concentrations were 84.7+/-5.8, 92.3+/-3.4 and 89.9+/-5.1%. After administration of SMEDDS and tablets to rabbits, significant differences were found in main pharmacokinetic parameters of Tmax, Cmax and AUC(0-infinity) between these two formulations, and a 2.5-fold enhancement of relative bioavailability of ATT was observed from the SMEDDS compared with tablets.

Interaction of naproxen with ionic cyclodextrins in aqueous solution and in the solid state

The possible role of the cyclodextrin charge in the interaction with an acidic drug such as naproxen (pKa 4.8) has been evaluated. Sulfobutylether-beta-cyclodextrin (SBE-betaCyd) and trimethylammonium-beta-cyclodextrin (TMA-betaCyd) were selected as, respectively, anionically and cationically charged carriers and their performance was compared with that of the parent beta-cyclodextrin (betaCyd) and of its methyl-derivative (Me betaCyd) previously found as the best partner for the drug. Interactions in solution were investigated by phase-solubility, fluorescence and circular dichroism analyses. Equimolar drug-carrier products prepared by different techniques (blending, cogrinding, sealed-heating, colyophilization) were characterized by differential scanning calorimetry and X-ray powder diffractometry and tested for drug dissolution properties. Anionic charges of SBE-betaCyd did not negatively influence interactions in unbuffered aqueous solutions (pH approximately 5) with the acidic drug. In fact, it was a very effective carrier, exhibiting solubilizing and complexing properties considerably better than the parent betaCyd and comparable to those of Me betaCyd. On the contrary, the positive charges of TMA-betaCyd did not favour interactions with the counter-ionic drug (despite the presence of about 60% ionised drug) and it was less efficacious also than native betaCyd. Therefore, the role of the Cyd charge on the complexing and solubilizing properties towards naproxen was not important whereas other factors, such as steric hindrance effects and favourable hydrophobic interactions were significant in determining the drug affinity for the Cyd inclusion. Solid state studies evidenced similar amorphizing properties of both charged Cyds towards naproxen. On the other hand, dissolution tests, in agreement with solution studies, showed that all products with SBE-betaCyd exhibited significantly better dissolution properties than the corresponding ones with TMA-betaCyd. A clear influence of the preparation method of drug-Cyd solid systems on the performance of the end product was also observed. Colyophilization was the most effective technique, followed by the cogrinding one. Colyophilized product with SBE-betaCyd allowed a 10-times increase in drug dissolution efficiency (D.E.) (with respect to the five-times increase obtained with the corresponding coground product) and a reduction of t(50%) from about 60 min (for the coground product) to less than 2 min.

Physicochemical and structural characterization of quercetin-beta-cyclodextrin complexes

Quercetin is a bioactive flavonoid widely used as a health supplement. Being sparingly soluble and chemically unstable in aqueous intestinal fluids, quercetin is poorly absorbed orally. This study aimed to investigate the effects of three beta-cyclodextrins, namely, unsubstituted beta-cyclodextrin (beta-CD), hydroxypropyl-beta-cyclodextrin (HP-beta-CD), and sulfobutyl ether beta-cyclodextrin (SBE-beta-CD) on the chemical stability and water solubility of quercetin, and to elucidate the complexation mechanisms of these beta-CDs with quercetin. Quercetin-beta-CD complexes in solution were characterized by stability assessment, phase solubility measurements, and 1H-nuclear magnetic resonance (NMR) spectroscopy. Molecular modeling was used to help establish the mode of interaction of the beta-CDs with quercetin. Solubility enhancements of quercetin obtained with the three beta-CDs followed the rank order: SBE-beta-CD > HP-beta-CD > beta-CD. The stability of quercetin at alkaline pHs also showed substantial improvement. NMR spectroscopic analysis suggested that the B-ring, C-ring, and part of the A-ring of quercetin display favorable interaction with the hydrophobic cavity of the beta-CDs, which was confirmed by molecular dynamics (MD) simulations using a solvated model of the quercetin-beta-CD complex. An inclusion complex model has been established for explaining the observed augmentation of solubility and stability of quercetin in water by beta-CDs.

Preparation of prostaglandin E1-hydroxypropyl-β-cyclodextrin complex and its nasal delivery in rats

The potential use of hydroxypropyl-beta-cyclodextrin (HP-betaCD) in the solubilization and stabilization of prostaglandin E(1) (PGE(1)) was investigated. The solubility and chemical stability of PGE(1) were significantly improved upon complexation with HP-betaCD. The nasal delivery of PGE(1) from the complex formulation was also studied in Wistar rats and compared with intravenous administration. PGE(1) complex after nasal administration caused a rapid decrease of blood pressure and exhibited an obvious dose-efficacy relationship, showing results nearly similar to those obtained for intravenous route. The time to reach the peak effect (T(max)) was approximately 3-4 min. Except T(max), other pharmacodynamic parameter values such as the maximal percent of blood pressure decrease (E(max), %), the lasting time of effect (T(d)), and the area under the curve (AUC, blood pressure decrease % min) were increased with increasing the administered doses. The E(max), T(d), and in particular AUC values between doses were significantly different (P < 0.01), but T(max) between doses were not significantly different (P < 0.05). The AUC values per unit dose of PGE(1) for nasal administration, however, were smaller than those for intravenous route, probably due to the incomplete absorption of nasally administered PGE(1). Besides, the in vitro effect of the PGE(1) complex on nasal mucociliary movement was also investigated with a toad palate model. The PGE(1) complex formulation exerted only minor effect on nasal mucociliary movement. These results indicate that the PGE(1)-HP-betaCD complex formulation for nasal delivery is a very promising preparation with advantages such as rapid and effective absorption, good chemical stability, ease of administration, and minor nasal ciliotoxicity.

In vitro controlled release of vinpocetine-cyclodextrin-tartaric acid multicomponent complexes from HPMC swellable tablets

The objective of this study was to investigate the effect of multicomponent complexation (MCC) of vinpocetine (VP), a poorly soluble base-type drug, with beta-cyclodextrin (betaCD), sulfobutylether beta-cyclodextrin (SBEbetaCD), tartaric acid (TA), polyvinylpyrrolidone (PVP) and hydroxypropylmethylcellulose (HPMC), on the design of controlled release hydrophilic HPMC tablets and to evaluate their in vitro release profiles by a pH gradient method. Multicomponent complexation led to enhanced dissolution properties of VP both in simulated gastric and intestinal fluids, and became possible the development of HPMC tablet formulations with more independent pH dissolution profiles. Drug release process was investigated experimentally using USP apparatus 3 and by means of model-independent parameters. Responses studied included similarity of dissolution profiles, time for 60% of the drug to dissolve (T(60%)), percent of VP released after 7 h (PD(7 h)) and the dissolution efficiency parameter at 12 h (DE(12 h)). Influence of multicomponent complexation was proved to increase the release of VP from HPMC tablets and superior PD(7 h) and DE(12 h) values were obtained in formulations containing VP-CD-TA complexes. Results supported the use of HPMC matrices to provide a useful tool in retarding the release of VP and that dissolution characteristics of the drug may be modulated by multicomponent complexation in these delivery systems, suggesting an improvement on VP bioavailability.

Effect of Hydroxypropyl β‐Cyclodextrin on Drug Solubility in Water‐Propylene Glycol Mixtures

Combined effects of cosolvency and inclusion complexation on drug solubility were studied using a model hydrophobic compound (carbamazepine) and a model hydrophilic compound (Compound S). Propylene glycol (PG) was used as the nonaqueous solvent, and deionized water was employed for the aqueous systems. Hydroxypropyl beta-cyclodextrin (HPbetaCD) was chosen as the complexing agent and studied at concentrations up to 28% (w/v). Complex formation constants (Kc) and solubility enhancement ratios were determined for the respective compounds in various water/PG vehicles. The data suggested that the inclusion of the compounds was most favorable when water alone was used as the vehicle. However, the combined approach of cosolvency and complexation resulted in a significant increase in the total apparent solubility of carbamazepine (the hydrophobic compound). The same was not observed with Compound S (the hydrophilic model), since PG weakened the interactions between the molecule and HPbetaCD, and thus, no synergistic or additive effects were observed with the combined approach of complexation and cosolvency.

Toward the Development of an Injectable Dosage Form of Propofol: Preparation and Evaluation of Propofol–Sulfobutyl Ether 7‐β‐Cyclodextrin Complex

The objectives of the present study were to undertake activities toward the development of an aqueous-based formulation of propofol (2,6-diisopropyl phenol), using sulfobutylether 7-beta-cyclodextrin (SBECD). Preformulation studies, including high performance liquid chromatography (HPLC) method development and phase-solubility evaluation in the presence of SBECD were conducted. It was determined that equilibrium solubility has been reached by 4-day and 7-day phase-solubility analysis at 30 degrees C and 37 degrees C. The apparent binding constants and various thermodynamic parameters were calculated from this data. These results suggest that "nonclassical hydrophobic effects" are the driving forces for inclusion complex formation. Compounding and lyophilization of the formulation with 20% SBECD yielded a product with propofol concentration of 10 mg/mL. The formulation properties were probed by using techniques that included modulated differential scanning calorimetry (MDSC) and Karl Fischer analysis. MDSC showed that propofol, SBECD, and the Propofol-SBECD complex displayed thermal properties at widely varying temperatures, suggesting the formation of a new solid form. The active pharmaceutical ingredient in the liquid formulation and lyophilized product was determined by the newly developed and qualified HPLC method. Short-term stability studies of the liquid formulation showed that they were stable for a month at 4 degrees C. Short-term stability studies of the freeze-dried cakes showed that the product was stable for over a month at 4 degrees C, 37 degrees C, and 50 degrees C. Based on these preliminary results, we believe that an aqueous based injectable formulation of propofol with sulfobutylether 7-beta-cyclodextrin can be successfully developed.

Physicochemical investigation of the effects of water-soluble polymers on vinpocetine complexation with β-cyclodextrin and its sulfobutyl ether derivative in solution and solid state

The studies reported in this work aimed to elucidate the inclusion complex formation of vinpocetine (VP), a poorly water-soluble base type drug, with beta-cyclodextrin (betaCD) and its sulfobutyl ether derivative (sulfobutyl ether beta-cyclodextrin (SBEbetaCD)), with or without water-soluble polymers (PVP and HPMC), by thoroughly investigating their interactions in solution and solid state. Phase solubility studies were carried out to evaluate the solubilizing power of both cyclodextrins (CDs), in association with water-soluble polymers, towards VP and to determine the apparent stability constants (Kc) of the complexes. SBEbetaCD showed higher solubilizing efficacy toward VP than the parent betaCD due to its greater solubility and complexing abilities, what was reflected in higher Kc values. Improvement in Kc values for ternary complexes clearly proves the benefit on the addition of water-soluble polymers to promote higher complexation efficiency. VP-CDs (1:1) binary and ternary systems were prepared by physical mixing, kneading, co-evaporation, and lyophilization methods. In the solid state, drug-carrier interactions were studied by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), X-ray diffractometry (XRD) and Fourier-transform infrared spectroscopy. The results of these analysis suggested the formation of new solid phases, some of them in amorphous state, allowing to the conclusion of strong evidences of binary and ternary inclusion complex formation between VP, CD and water-soluble polymers, particularly for co-evaporated and lyophilized binary and ternary products.

Formation of fine drug particle by cogrinding with cyclodextrins

The purpose of this study was to investigate the effect of moisture condition during cogrinding process on fine drug particle formation. Cogrinding of cyclodextrins (CDs) and pranlukast (PRK) hemihydrate was performed in various moisture conditions at a mixing molar ratio of 2:1 (CDs:PRK) and the formation of PRK submicron particle was investigated. The moisture content in the cogrinding process significantly affected the fine particle formation. More than 90% of pranlukast loaded transformed to submicron particles when coground with alpha-CD, beta-CD or gamma-CD containing the specific amount of water for each CD system. Fine particle formation of PRK was considered as a particular phenomenon to cyclodextrins, since the submicron particles could not be formed when D-mannitol, lactose or microcrystalline cellulose (MCC) was used as a cogrinding additive. Moreover, the appearance and disappearance of fine particle formation was found to be reversible depending on the existence of water during the grinding process.

Investigation and physicochemical characterization of vinpocetine-sulfobutyl ether beta-cyclodextrin binary and ternary complexes

The purpose of this study was to investigate the interactions between vinpocetine (VP), sulfobutyl ether beta-cyclodextrin (SBEbetaCD) and the water-soluble polymers polyvinylpyrrolidone (PVP) and hydroxypropyl methylcellulose (HPMC). The water-soluble polymers were shown to improve the complexation efficiency of SBEbetaCD, and thus less SBEbetaCD was needed to prepare solid VP-SBEbetaCD complexes in the presence of the polymers. The interactions between VP and SBEbetaCD, with or without PVP or HPMC, were thoroughly investigated in aqueous solutions using the phase-solubility method as well as in the solid state. The amount of VP solubilized in water or aqueous polymer solution increased linearly with increasing SBEbetaCD concentration, demonstrating A(L)-type plots. We estimated the apparent stability constant (K(c)) at room temperature of VP-SBEbetaCD binary complex to be 340 M(-1) and this value increased to 490 M(-1) or 390 M(-1), respectively, with the addition of PVP and HPMC, assuming a 1 : 1 VP-SBEbetaCD molar ratio. Improvement in the K(c) values for ternary complexes clearly confirmed the benefit of the addition of water-soluble polymers to promote higher complexation efficiency. Solid VP-SBEbetaCD binary and ternary systems were prepared by physical mixing, kneading, coevaporation, and lyophilization methods and fully characterized by scanning electron microscopy, differential scanning calorimetry, and X-ray diffractometry. The results obtained suggest that coevaporation and lyophilization methods yield a higher degree of amorphous entities and indicated formation of VP-SBEbetaCD binary and ternary complexes.

Spray-dried redispersible oil-in-water emulsion to improve oral bioavailability of poorly soluble drugs

A physically stabilized dry emulsion dosage form reforming the original emulsion after rehydration was developed by spray-drying a liquid oil-in-water emulsion containing maltodextrin as carrier and sodium caseinate as emulsifying agent. Several oil:water as well as maltodextrin:water ratios were tested, the homogenization and spray-drying processes and the reconstitution properties were investigated and an optimum formulation was selected for poorly soluble drug incorporation, having an identical oil:water and carrier:water ratio of 10% (w/w) and a load of solid material of 20% (w/w). Lipophilic 5-phenyl-1,2-dithiole-3-thione (5-PDTT) was selected as a model drug. 5-PDTT release from the solid state emulsion was studied using an in vitro two-phase stirred model and the relative bioavailability of 5-PDTT in the dry emulsion was obtained in the rabbit after oral administration of the reconstituted emulsion, compared to a 5-PDTT-sulfobutyl ether 7 beta-cyclodextrin complex in solution. Incorporation of 5-PDTT in the oil phase neither affects the surface morphology of the powder nor the reconstitution, the droplet size or the drug releasing properties and, furthermore, allows a 3-fold improvement of 5-PDTT relative bioavailability in rabbit after oral administration. These results indicate that dry emulsions may be considered as relevant dosage forms to improve bioavailability of poorly absorbable lipophilic drugs.

Thermal analysis and spectroscopic characterization of interactions between a naphthoquinone derivative with HP-beta-CD or PVP

The purpose of the present study was to investigate the interaction between both hydroxypropyl-beta-cyclodextrin (HP-beta-CD) and PVP-K30 with 2-hydroxy-N-(3-methyl-5-ethyl-4-isoxazolyl)-1,4-naphthoquinone-4-imina (I), a synthetic derivative of isoxazolylnaphthoquinones that has demonstrated to exhibit important biological activity against S. aureus and T. cruzi. The continuous variation plot for I-HP-beta-CD system showed a 1:1 stoichiometry for the complex. Ultraviolet absorption spectroscopy indicates that the isoxazole moiety of I is preferably incorporated in the cavity. Furthermore, proton nuclear magnetic resonance spectroscopy suggests that this incorporation is made from the primary hydroxyl group side of the cyclodextrin. The validation of this incorporation is further evidenced by thermal analysis (DSC and TGA) and infrared spectroscopy. I-PVP-K30 interactions in solid state were demonstrated by combining the infrared spectroscopy data with the results of thermal analysis (DSC, TGA). These methods suggest that drug-polymer interaction probably occurs via intermolecular hydrogen bonding between the drug hydroxyl and polymer carbonyl groups.

Physicochemical characterization and in vitro dissolution behavior of nicardipine-cyclodextrins inclusion compounds

Inclusion complexation between nicardipine hydrochloride (NC), a calcium-channel antagonist, and beta-cyclodextrin (beta-CD) or hydroxypropyl-beta-cyclodextrin (HPbetaCD) was evaluated in aqueous environment and in solid state. The phase solubility profiles with both cyclodextrins (CDs) were classified as A(L)-type, indicating the formation of 1:1 stoichiometric inclusion complexes. Stability constants (Ks) were calculated from the phase solubility diagrams and were found to be pH dependent. More stable NC:CDs complexes were formed in alkaline medium in which the drug is in its non-ionized form. Binary systems of NC with CDs, prepared experimentally by different techniques (kneading, evaporation, freeze-drying and spray-drying), were investigated by differential scanning calorimetry, Fourier transformation-infrared spectroscopy, X-ray diffractometry and scanning electron microscopy. From this analysis, evaporation, freeze-drying and spray-drying were found to produce inclusion complexes. In contrast, crystalline drug was still clearly detectable in the kneaded products. The dissolution profiles of the obtained powders were studied in order to define the most appropriate CD and preparation method to originate inclusion complexes, which will be used in the development of a new controlled release formulation of NC. Both the preparation and nature of carrier played an important role in the dissolution performance of the system. However, independently of the preparation technique, all the combinations with HPbetaCD were more effective in achieving the enhancement of the NC dissolution rate, yielding better performances than the corresponding ones with betaCD.