Study of the inclusion complex of atenolol with beta-cyclodextrins

Biotinylated Cyclooligosaccharides for Paclitaxel Solubilization

The poor water solubility of paclitaxel causes significant problems in producing cancer therapeutic formulations. Here, we aimed to solubilize paclitaxel using biocompatible cyclic carbohydrates. Generally recognized as safe, labeled β-cyclodextrin (β-CD), a cyclic α-1,4-glucan consisting of seven glucoses, was prepared, and bio-sourced cyclosophoraoses (CyS), which are unbranched cyclic β-1,2-glucans with 17-23 glucose units, were purified using various chromatographic methods from Rhizobium leguminosarum cultural broth. For effective targeting, CyS and β-CD were modified with a biotinyl moiety in a reaction of mono-6-amino CyS and mono-6-amino-β-CD with N-hydroxysuccinimide ester of biotinamidohexanoic acid. Interestingly, the aqueous solubility of paclitaxel was enhanced 10.3- and 3.7-fold in the presence of biotinyl CyS and biotinyl β-CD, respectively. These findings suggest that biotin-appended cyclooligosaccharides can be applied to improve the delivery of paclitaxel.

The influence of non-ionisable excipients on precipitation parameters measured using the CheqSol method

OBJECTIVES

The aim of this study was to determine the influence of non-ionisable excipients hydroxypropyl-β-cyclodextrin (HPβCD) and poloxamers 407 and 188 on the supersaturation and precipitation kinetics of ibuprofen, gliclazide, propranolol and atenolol induced through solution pH shifts using the CheqSol method.

METHODS

The drug's kinetic and intrinsic aqueous solubilities were measured in the presence of increasing excipient concentrations using the CheqSol method. Experimental data rate of change of pH with time was also examined to determine excipient-induced parachute effects and influence on precipitation rates.

KEY FINDINGS

The measured kinetic and intrinsic solubilities provide a determination of the influence of each excipient on supersaturation index, and the area under the CheqSol curve can measure the parachute capability of excipients. The excipients influence on precipitation kinetics can be measured with novel parameters; for example, the precipitation pH or percentage ionised drug at the precipitation point, which provide further information on the excipient-induced changes in precipitation performance.

CONCLUSION

This method can therefore be employed to measure the influence of non-ionisable excipients on the kinetic solubility behaviour of supersaturated solutions of ionisable drugs and to provide data, which discriminates between excipient systems during precipitation.

Supramolecular Complexation of Carbohydrates for the Bioavailability Enhancement of Poorly Soluble Drugs

In this review, a comprehensive overview of advances in the supramolecular complexes of carbohydrates and poorly soluble drugs is presented. Through the complexation process, poorly soluble drugs could be efficiently delivered to their desired destinations. Carbohydrates, the most abundant biomolecules, have diverse physicochemical properties owing to their inherent three-dimensional structures, hydrogen bonding, and molecular recognition abilities. In this regard, oligosaccharides and their derivatives have been utilized for the bioavailability enhancement of hydrophobic drugs via increasing the solubility or stability. By extension, polysaccharides and their derivatives can form self-assembled architectures with poorly soluble drugs and have shown increased bioavailability in terms of the sustained or controlled drug release. These supramolecular systems using carbohydrate will be developed consistently in the field of pharmaceutical and medical application.

Formulation and evaluation of fixed-dose combination of bilayer gastroretentive matrix tablet containing atorvastatin as fast-release and atenolol as sustained-release

The objective of the present study was to develop bilayer tablets of atorvastatin and atenolol that are characterized by initial fast-release of atorvastatin in the stomach and comply with the release requirements of sustained-release of atenolol. An amorphous, solvent evaporation inclusion complex of atorvastatin with β-cyclodextrin, present in 1 : 3 (drug/cyclodextrin) molar ratio, was employed in the fast-release layer to enhance the dissolution of atorvastatin. Xanthan gum and guar gum were integrated in the sustained-release layer. Bilayer tablets composed of sustained-release layer (10% w/w of xanthan gum and guar gum) and fast-release layer [1 : 3 (drug/cyclodextrin)] showed the desired release profile. The atorvastatin contained in the fast-release layer showed an initial fast-release of more than 60% of its drug content within 2 h, followed by sustained release of the atenolol for a period of 12 h. The pharmacokinetic study illustrated that the fast absorption and increased oral bioavailability of atorvastatin as well as therapeutic concentration of atenolol in blood were made available through adoption of formulation strategy of bilayer tablets. It can be concluded that the bilayer tablets of atorvastatin and atenolol can be successfully employed for the treatment of hypertension and hypercholesterolemia together through oral administration of single tablet.

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.

Advanced technologies for oral controlled release: cyclodextrins for oral controlled release

Cyclodextrins (CDs) are used in oral pharmaceutical formulations, by means of inclusion complexes formation, with the following advantages for the drugs: (1) solubility, dissolution rate, stability, and bioavailability enhancement; (2) to modify the drug release site and/or time profile; and (3) to reduce or prevent gastrointestinal side effects and unpleasant smell or taste, to prevent drug-drug or drug-additive interactions, or even to convert oil and liquid drugs into microcrystalline or amorphous powders. A more recent trend focuses on the use of CDs as nanocarriers, a strategy that aims to design versatile delivery systems that can encapsulate drugs with better physicochemical properties for oral delivery. Thus, the aim of this work was to review the applications of the CDs and their hydrophilic derivatives on the solubility enhancement of poorly water-soluble drugs in order to increase their dissolution rate and get immediate release, as well as their ability to control (to prolong or to delay) the release of drugs from solid dosage forms, either as complexes with the hydrophilic (e.g., as osmotic pumps) and/or hydrophobic CDs. New controlled delivery systems based on nanotechnology carriers (nanoparticles and conjugates) have also been reviewed.

Spectroscopic investigations and crystal structure from synchrotron powder data of the inclusion complex of beta-cyclodextrin with atenolol

Inclusion complexes of atenolol with beta-cyclodextrin (beta-CD) in aqueous solution have been investigated with 1H NMR and UV-vis spectroscopy. The stoichiometry of this inclusion complex was established to be equimolar (1:1) and its stability constant was determined by UV-vis spectroscopy. The crystal structure of the beta-CD-atenolol (1:1) inclusion compound has been solved from synchrotron powder diffraction data using direct-space search techniques. The crystal structure model and 1H NMR data are in good agreement and, with support of Hyperchem MM+ molecular dynamics results, suggest which protons are likely to be involved in the inclusion process that leads to the supramolecular architecture of this guest-host complex.

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.

Physicochemical properties and dissolution studies of dexamethasone acetate-beta-cyclodextrin inclusion complexes produced by different methods

Inclusion complexes between dexamethasone acetate (DMA), a poorly water soluble drug, and beta-cyclodextrin (betaCD) were obtained to improve the solubility and dissolution rate of this drug. Phase-solubility profile indicated that the solubility of DMA was significantly increased in the presence of betaCD (33-fold) and was classified as A(L)-type, indicating the 1:1 stoichiometric inclusion complexes. Solid complexes prepared by different methods (kneading, coevaporation, freeze drying) and physical mixture were characterized by differential scanning calorimetry, thermogravimetry, infrared absorption and optical microscopy. Preparation methods influenced the physicochemical properties of the products. The dissolution profiles of solid complexes were determined and compared with those DMA alone and their physical mixture, in three different mediums: simulated gastric fluid (pH 1.2), simulated intestinal fluid (pH 7.4) and distilled water. The dissolution studies showed that in all mediums DMA presented an incomplete dissolution even in four hours. In contrast, the complexes formed presented a higher dissolution rate in simulated gastric fluid (SGF pH 1.2), which indicate that these have different ionization characteristics. According to the results, the freeze-dried and kneaded products exhibited higher dissolution rates than the drug alone, in all the mediums.

Solubility-modulated monolithic osmotic pump tablet for atenolol delivery

A method for the preparation of monolithic osmotic pump tablet was obtained by modulating atenolol solubility with acid. Tartaric acid was used as solubility promoter, sodium chloride as osmotic agent and polyvinyl pyrrolidone as retardant agent. Ethyl cellulose was employed as semipermeable membrane containing polyethylene glycol 400 as plasticizer. The formulation of atenolol monolithic osmotic pump tablet was optimized by orthogonal design and evaluated by similarity factor (f(2)). The optimal monolithic osmotic pump tablet was found to be able to deliver atenolol at the rate of approximate zero-order up to 24h, independent of release media and agitation rate. The approach of solubility-modulated by acid-alkali reaction might be used for the preparation of osmotic pump tablet of other poorly water-soluble drugs with alkaline or acid groups.

Enhanced bioavailability of poorly water-soluble clotrimazole by inclusion with β-cyclodextrin

Clotrimazole, a poorly water-soluble antimycotic agent, is a promising agent for various diseases including cancer and sickle cell anemia. To improve the oral bioavailability of clotrimazole, the inclusion compound of clotrimazole with beta-cyclodextrin was prepared by spray-drying method and characterized by phase solubility, differential scanning calorimetry and dissolution. Furthermore, the pharmacokinetics after oral administration in rats was then performed compared with clotrimazole powder. The solubility of clotrimazole increased linearly as a function of beta-cyclodextrin concentration, resulting in A(L) type phase solubility diagram which revealed a formation of inclusion compound in a molar ratio of 1:2, with the apparent association constant of 230.2 M(-1). The dissolution rate of clotrimazole in the inclusion compound increased greatly compared to clotrimazole powder in pH 7.4 phosphate buffer solution. The inclusion compound gave significantly higher initial plasma concentrations, Cmax and AUC of clotrimazole than did clotrimazole powder when they were administered as suspension form, indicating that the drug from inclusion compound could be more orally absorbed in rats. Thus, the oral bioavailability of clotrimazole could be improved markedly by inclusion complexation, possibly due to an increased dissolution rate.

A molecular inclusion complex of atenolol with 2-hydroxypropyl-β-cyclodextrin: The production and characterization thereof

The molecular inclusion complex of atenolol with 2-hydroxypropyl-?-cyclodextrin was synthesized using the coprecipitation method. The complex obtained was characterized by FT-IR, 1H-NMR, 13C-NMR spectroscopy, as well as by DSC and X-ray diffraction analysis. The DSC analysis confirmed the existence of the complex with the endothermic atenolol melting peak at about 155?C disappearing. The X-ray diffraction patterns of the complex and 2-hydroxypropyl-?-cyclodextrin were very similar, thus confirming the complete inclusion of the atenolol molecule within the cavity of the 2-hydroxypropyl-?-cyclodextrin. The peaks originating from atenolol were completely absent in the diffractogram of the complex. 1H-NMR and 13C-NMR spectra showed certain changes in the chemical shifts of protons and C atoms from atenolol and 2-hydroxypropyl-?-cyclodextrin, indicating that a complex had been formed and also which protons participated in the hydrogen bonds which formed the complex. The atenolol solubility in water was improved (254 mg complex cm-3, i.e., 37.5 mg atenolol cm-3), and in pH 3 HCl solution (251 mg complex cm-3, i.e., 37 mg atenolol cm-3) when compared to pure atenolol, and even when compared to the atenolol complex with ?-cyclodextrin. The increased solubility ensures greater bioavailability of the active component and, due to the low solubility, significantly corrects for the lack of the basic active substance and, simultaneously, increases its overall therapeutic effect, combined with reduced side effects. .

The physicochemical characteristics of freeze-dried scutellarin-cyclodextrin tetracomponent complexes

In an effort to improve the solubility of the insoluble drug scutellarin, a novel complexation of scutellarin with beta-cyclodextrin (beta-CD) was studied. Tetracomponent freeze-dried complex was prepared with scutellarin, beta-CD, Hydroxypropyl Methylcellulose (HPMC), and triethanolamine. To confirm complex formation, complex was characterized by Fourier transform infrared spectroscopy (FT-IR), powder X-ray diffraction, and differential scanning calorimetry (DSC). Phase-solubility analysis suggested the soluble complexes having 1:1 stoichiometry. The beta-CD solubilization of scutellarin could be improved significantly by combining water-soluble polymer and pH adjuster. Comparing the binary, ternary solid systems with tetrary systems, tetracomponent freeze-dried complex showed the best effect of solubilization. A maximal solubility of scutellarin (23.65 mg/ml) was achieved with tetracomponent freeze-dried complex, up to 148-fold increase over scutellarin solubility in water, and the solubility of scutellarin is 15.35 microg/ml (up to 6-fold) in simulated gastric fluid.

Insights into cyclodextrin interactions during sample stacking using capillary isotachophoresis with on-line microcoil NMR detection

On-line capillary isotachophoresis (cITP)-NMR experiments were used to probe the interactions of the pharmaceutical compounds S-alprenolol, S-atenolol, R-propranolol, R-salbutamol and S-terbutaline with beta-cyclodextrin (beta-CD) during cITP concentration. In cITP, ionic analytes are concentrated and separated on the basis of their electrophoretic mobility. Because neutral molecules have an electrophoretic mobility of zero, they are normally not concentrated or separated in electrophoretic experiments like cITP. Most of the analytes studied were concentrated by cITP sample stacking by a factor of around 300. For analytes that formed a strong inclusion complex, beta-CD co-concentrated during cITP sample stacking. However, once the focusing process was complete, a discrete diffusional boundary formed between the cITP-focused analyte band and the leading and trailing electrolyte, which restricted diffusion into and out of the analyte band.

Preformulation study of the inclusion complex warfarin-beta-cyclodextrin

Inclusion complex between warfarin and beta-cyclodextrin was obtained to improve the in vitro bioavailability of the drug in acidic media. Inclusion complexation in solution was studied by phase solubility technique. The apparent stability constant was influenced by the pH of the medium ranging from 633.26 M(-1) (at pH 1.2, where the drug was in unionised form) to 99.81 M(-1) (at pH 7.4, where the drug was in ionised form). Phase solubility study showed an AL-type diagram indicating the formation of an inclusion complex in 1:1 molar ratio. Solid binary mixtures of the drug with beta-cyclodextrin were prepared by several methods (physical mixing, kneading, co-evaporation, freeze-drying). Physicochemical characterizations were performed using differential scanning calorimetry, powder X-ray diffractometry and dissolution studies. Preparation method influenced the physicochemical properties of the binary mixtures. An inclusion complex was obtained by freeze-drying, and it showed a high solubility and drug dissolution rate. The physical stability of the complex was also studied. After one year storage in glass container at room temperature no significant changes were detected in the diffractogram, thermogram and dissolution profile of the freeze-dried product.

Effects of alpha- and beta-cyclodextrin complexation on the physico-chemical properties and antioxidant activity of some 3-hydroxyflavones

Inclusion complexes of some flavonols (3-hydroxyflavone, morin and quercetin) have been obtained with alpha- and beta-cyclodextrins, by the co-evaporation method. Different analytical techniques (DSC, XRPD, FT-IR, 1H-NMR, UV-Vis) have been employed for a throughout investigation of the structural characteristics of such supramolecular aggregates, which exhibited distinct spectroscopic features and properties from both "guest" and "host" molecules. The stoichiometric ratios and stability constants describing the extent of formation of the complexes have been determined by phase-solubility studies; in all cases type-AL diagrams have been obtained (soluble 1:1 complexes). The effect of molecular encapsulation on the flavonols antioxidant activity has been afterwards evaluated, by means of different biological assays (Bathophenanthroline test; Comet assay; Lipid peroxidation). Complexation with cyclodextrins further improved the antioxidant activity, increasing drugs solubility in the biological moiety.

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.

The effect of pH and triethanolamine on sulfisoxazole complexation with hydroxypropyl-beta-cyclodextrin

A novel complexation of sulfisoxazole with hydroxypropyl-beta-cyclodextrin (HP-beta-CD) was studied. Two systems were used: binary complexes prepared with HP-beta-CD and multicomponent system (HP-beta-CD and the basic compound triethanolamine (TEA)). Inclusion complex formation in aqueous solutions and in solid state were investigated by the solubility method, thermal analysis (differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA)), Fourier-transform infrared spectroscopy (FT-IR) and dissolution studies. The solid complexes of sulfisoxazole were prepared by freeze-drying the homogeneous concentrated aqueous solutions in molar ratios of sulfisoxazole:HP-beta-CD 1:1 and 1:2, and sulfisoxazole:TEA:HP-beta-CD 1:1:2. FT-IR and thermal analysis showed differences among sulfisoxazole:HP-beta-CD and sulfisoxazole:TEA:HP-beta-CD and their corresponding physical mixtures and individual components. The HP-beta-CD solubilization of sulfisoxazole could be improved by ionization of the drug molecule through pH adjustments. However, larger improvements of the HP-beta-CD solubilization are obtained when multicomponent systems are used, allowing to reduce the amount of CD necessary to prepare the target formulation.

Improvement of Dissolution and Bioavailability of Nitrendipine by Inclusion in Hydroxypropyl-β-cyclodextrin

A significant increase in solubility and dissolution rate of nitrendipine, a slightly soluble calcium channel blocker, was achieved by inclusion complexation with hydroxypropyl-beta-cyclodextrin (HP-beta-CD). The inclusion complex was prepared by solvent evaporation method and characterized by phase solubility method, x-ray diffractometry, infrared spectroscopy, and differential scanning calorimetry. The solubility of nitrendipine increased linearly as a function of HP-beta-CD concentration, resulting in AL-type phase solubility diagram which revealed a formation of inclusion complex in a molar ratio of 1:1, with the apparent association constant of 108.3M(-1). The in vitro dissolution rate of nitrendipine in pH 7.4 phosphate buffer was in the order of inclusion complex, physical mixture, and nitrendipine powder. These three different forms of nitrendipine were administered orally to rats with a dose of 10 mg/kg equivalent to nitrendipine. The AUC of inclusion complex was significantly larger than that of nitrendipine powder. Tmax of inclusion complex was significantly shorter and Cmax was significantly higher than those of nitrendipine powder. Cmax of physical mixture was higher than that of nitrendipine powder. Tmax of physical mixture, however, remained the same. The results indicated that the bioavailability of nitrendipine could be improved markedly by inclusion complexation, possibly due to an increased dissolution rate.