Preparation and characterization of albendazole beta-cyclodextrin complexes

The Use of Cyclodextrin Inclusion Complexes to Increase the Solubility and Pharmacokinetic Profile of Albendazole

Albendazole is the preferred deworming drug and has strong insecticidal effects on human and animal helminth parasites, showing remarkable activity against hepatocellular carcinoma and colorectal cancer cells. However, it is classified as being in class II in the Biopharmaceutics Classification System due to its poor water solubility (0.2 mg/L) and high permeability, which make the clinical application of albendazole impractical. Through complexation with methyl-β-cyclodextrin, as the best result so far, albendazole's water solubility was increased by 150,000 times, and albendazole could be 90% released during the first 10 min. In an in vivo pharmacokinetic study, the Cmax and Tmax of the active metabolized sulfoxide were changed from 2.81 µg/mL at 3 h to 10.2 µg/mL at 6 h and the AUC0-48 was increased from 50.72 h⁎μg/mL to 119.95 h⁎μg/mL, indicating that the inclusion complex obtained can be used as a new oral therapeutic anti-anthelmintic and anti-tumor agent formulation.

Recent Advances in the Pharmaceutical and Biomedical Applications of Cyclodextrin-Capped Gold Nanoparticles

The real problem in pharmaceutical preparation is drugs' poor aqueous solubility, low permeability through biological membranes, and short biological t_1/2. Conventional drug delivery systems are not able to overcome these problems. However, cyclodextrins (CDs) and their derivatives can solve these challenges. This article aims to summarize and review the history, properties, and different applications of cyclodextrins, especially the ability of inclusion complex formation. It also refers to the effects of cyclodextrin on drug solubility, bioavailability, and stability. Moreover, it focuses on preparing and applying gold nanoparticles (AuNPs) as novel drug delivery systems. It also studies the uses and effects of cyclodextrins in this field as novel drug carriers and targeting devices. The system formulated from AuNPs linked with CD molecules combines the advantages of both CD and AuNPs. Cyclodextrins benefit in increasing aqueous drug solubility, loading capacity, stability, and size control of gold NPs. Also, AuNPs are applied as diagnostic and therapeutic agents because of their unique chemical properties. Plus, AuNPs possess several advantages such as ease of detection, targeted and selective drug delivery, greater surface area, high loading efficiency, and higher stability than microparticles. In the present article, we tried to present the potential pharmaceutical applications of CD-derived AuNPs in biomedical applications including antibacterial, anticancer, gene-drug delivery, and various targeted drug delivery applications. Also, the article highlighted the role of CDs in the preparation and improvement of catalytic enzymes, the formation of self-assembling molecular print boards, the fabrication of supramolecular functionalized electrodes, and biosensors formation.

Improvement of Antialveolar echinococcosis efficacy of novel Albendazole-Bile acids Derivatives with Enhanced Oral Bioavailability

Alveolar echinococcosis (AE) is a chronic and fatal infectious parasitic disease, which has not been well-researched. Current recommended therapies for AE by the World Health Organization include complete removal of the infected tissue followed by two years of albendazole (ABZ), administered orally, which is the only effective first-line anti-AE drug. Unfortunately, in most cases, complete resection of AE lesions is impossible, requiring ABZ administration for even longer periods. Only one-third of patients experienced complete remission or cure with such treatments, primarily due to ABZ's low solubility and low bioavailability. To improve ABZ bioavailability, albendazole bile acid derivative (ABZ-BA) has been designed and synthesized. Its structure was identified by mass spectrometry and nuclear magnetic resonance. Its physicochemical properties were evaluated by wide-angle X-ray diffraction, differential scanning calorimetry, scanning electron microscopy, and polarizing microscopy; it was compared with ABZ to assess its solubilization mechanism at the molecular level. To avoid the effects of bile acid on the efficacy of albendazole, the inhibitory effect of ABZ-BA on protoscolex (PSCs)s was observed in vitro. The inhibitory effect of ABZ-BA on PSCs was evaluated by survival rate, ultrastructural changes, and the expression of key cytokines during PSC apoptosis. The results showed that ABZ-BA with 4-amino-1-butanol as a linker was successfully prepared. Physicochemical characterization demonstrated that the molecular arrangement of ABZ-BA presents a short-range disordered amorphous state, which changes the drug morphology compared with crystalline ABZ. The equilibrium solubility of ABZ-BA was 4-fold higher than ABZ in vitro. ABZ-BA relative bioavailability (Frel) in Sprague-Dawley (SD) rats was 26-fold higher than ABZ in vivo. The inhibitory effect of ABZ-BA on PSCs was identical to that of ABZ, indicating that adding bile acid did not affect the efficacy of anti-echinococcosis. In the pharmacodynamics study, it was found that the ABZ-BA group had 2.7-fold greater than that of Albenda after 1 month of oral administration. The relative bioavailability of ABZ-BA is significantly better than ABZ due to the transformation of the physical state from a crystalline state to an amorphous state. Furthermore, sodium-dependent bile acid transporter (ASBT) expressed in the apical small intestine has a synergistic effect through the effective transport of bile acids. Therefore, we concluded that the NC formulation could potentially be developed to improve anti-AE drug therapy.

Nanocrystal Suspensions for Enhancing the Oral Absorption of Albendazole

Albendazole (ABZ), an effective benzimidazole antiparasitic drug is limited by its poor solubility and oral bioavailability. In order to overcome its disadvantages, ABZ nanocrystals were prepared using a novel bottom-up method based on acid-base neutralization recrystallization with high-speed mixing and dispersing. The cosolvent, stabilizer and preparation temperature were optimized using single factor tests. The physicochemical properties, solubility and pharmacokinetics of the optimal ABZ nanocrystals were evaluated. The high-performance liquid chromatography (HPLC), differential scanning calorimetry (DSC) and X-ray powder diffraction (XRD) showed that ABZ had no structural and crystal phase change after nanocrystallization. The saturated solubility of ABZ nanocrystals in different solvents was increased by 2.2-118 fold. The oral bioavailability of the total active ingredients (ABZ and its metabolites of albendazole sulfoxide (ABZSO) and albendazole sulfone (ABZSO2)) of the nanocrystals in rats was enhanced by 1.40 times compared to the native ABZ. These results suggest that nanocrystals might be a promising way to enhance the solubility and oral bioavailability of ABZ and other insoluble drugs.

Floating Ricobendazole Delivery Systems: A 3D Printing Method by Co-Extrusion of Sodium Alginate and Calcium Chloride

At present, the use of benzimidazole drugs in veterinary medicine is strongly limited by both pharmacokinetics and formulative issues. In this research, the possibility of applying an innovative semi-solid extrusion 3D printing process in a co-axial configuration was speculated, with the aim of producing a new gastro-retentive dosage form loaded with ricobendazole. To obtain the drug delivery system (DDS), the ionotropic gelation of alginate in combination with a divalent cation during the extrusion was exploited. Two feeds were optimized in accordance with the printing requirements and the drug chemical properties: the crosslinking ink, i.e., a water ethanol mixture containing CaCl₂ at two different ratios 0.05 M and 0.1 M, hydroxyethyl cellulose 2% w/v, Tween 85 0.1% v/v and Ricobendazole 5% w/v; and alginate ink, i.e., a sodium alginate solution at 6% w/v. The characterization of the dried DDS obtained from the extrusion of gels containing different amounts of calcium chloride showed a limited effect on the ink extrudability of the crosslinking agent, which on the contrary strongly influenced the final properties of the DDS, with a difference in the polymeric matrix toughness and resulting effects on floating time and drug release.

Cyclodextrin Dispersion of Mebendazole and Flubendazole Improves In Vitro Antiproliferative Activity

Mebendazole and flubendazole are antihelmintic drugs that have re-entered the research spotlight due to their exhibited anticancer effects, thus making them strong candidates as repurposed drugs. However, these benzimidazole derivatives exhibit poor solubility in water and various organic solvents, which limits their bioavailability. With the aim of obtaining an improved drug solubility and increased biological effect, mebendazole and flubendazole were complexed with 2-hydroxypropyl-β-cyclodextrin (HPBCD). The binary 1:1 conjugates were physicochemically evaluated by X-ray diffraction, thermal analysis, and FTIR spectroscopy, revealing the formation of physical mixtures. The increased aqueous solubility of the binary 1:1 conjugates vs. pure benzimidazole compounds was demonstrated by performing dissolution tests. The in vitro antiproliferative activity of mebendazole and flubendazole, as well as their combination with HPBCD, was tested on two cancer cell lines, human melanoma—A375 and pulmonary adenocarcinoma—A549 by the MTT assay. The cytotoxic activity manifested in a dose-dependent manner while the presence of HPBCD increased the antiproliferative activity against the targeted cells. Treatment of A375 and A549 cell lines with the binary conjugates induced a significant inhibition of mitochondrial respiration, as revealed by high-resolution respirometry studies. Molecular docking analysis showed that one of the mechanisms related to MEB and FLU cytotoxic activity may be due to the inhibition of MEK/ERK proteins.

Improvement of the Bioavailability and Anti-hepatic Alveolar Echinococcosis Effect of Albendazole-Isethionate/Hypromellose Acetate Succinate (HPMC-AS) Complex

Maximizing the pharmacodynamics of albendazole (ABZ), which is used to treat echinococcoses, is essential for the long-term treatment of echinococcosis patients. ABZ is a weak base whose solubility depends on the pH value of the solvent. After it has been orally administered, its solubility drops sharply from when it is in gastric juices (pH 1.4) to when it is in intestinal juices (pH 6.5) and is subsequently absorbed in the ileum and jejunum. This results in low solubility and poor bioavailability of the drug. In this study, we developed an orally administered albendazole-isethionate (ABZ-HES)/hypromellose acetate succinate (HPMC-AS) complex tablet (T_ABZ-HES-H) with improved solubility and bioavailability. Previous studies demonstrated that ABZ-HES has a higher intrinsic dissolution rate under pH 1.4 than the ABZ free base used in the commercial product Albenda and that HPMC-AS can effectively inhibit ABZ crystallization, which could be due to the hydrophobic interaction between ABZ and HPMC-AS in an aqueous environment. In this study, the dissolution behavior of T_ABZ-HES-H in vitro was studied by the two-step pH conversion method. Our results demonstrated that the oral bioavailability of T_ABZ-HES-H was approximately 2.6 times higher than that of ABZ. More importantly, in the rat model of secondary hepatic alveolar echinococcosis, the anti-hepatic alveolar echinococcosis effect of T_ABZ-HES-H was 3.4 times higher than that of a commercial product. The improved preparation with salt and polymer has proven to be a feasible method of improving the oral bioavailability and pharmacodynamics of ABZ.

Nanosuspension coated multiparticulates for controlled delivery of albendazole

OBJECTIVE

Improving solubility and bioavailability of albendazole (ALB).

SIGNIFICANCE

ALB is a broad-spectrum anthelminthic BCS class II drug with aqueous solubility of solubility of 4.1 mg/l at 25 °C and oral bioavailability of <5%.

METHODS

ALB nanosuspensions (NSs) were prepared by evaporative antisolvent precipitation using tocopherol polyethylene glycol succinate (TPGS) and polyvinyl pyrrolidone (PVP) as stabilizers and characterized for particle size, polydispersity index, and zeta potential. 3² factorial design was used to investigate effect of stabilizer concentration and speed of stirring on particle size. Concentration of TPGS was varied from 0.03 to 0.05% w/v and PVP K-30 was constant at 0.04% w/v. Stirring speed range was 1000-3000 rpm. Optimized NS was loaded on Espheres and coated with Eudragit S10& L100 and studied for friability, surface morphology and release kinetics.

RESULTS

Factorial experiments revealed pronounced effect of TPGS on particle size. Optimized batch had particle size of 251 ± 7.2 nm and zeta potential -16.2 ± 2.68 mV. Saturation solubility showed increase of 16-fold in water whereas in phosphate buffer increase was fourfold. ALB-NS secondary coated Espheres released 94.3% drug in 10 h whereas ALB-MS (microsuspension) coated Espheres showed 58% release. A 1.3-fold increase in AUC_0-10h was evident. Permeation from ALB-NS coated Espheres was 32% in 60 min while for ALB-MS coated Espheres it was 20%. Permeation increase occurred due to presence of TPGS which acts as a permeation enhancer.

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.

Improvement of Antialveolar Echinococcosis Efficacy of Albendazole by a Novel Nanocrystalline Formulation with Enhanced Oral Bioavailability

Alveolar echinococcosis (AE) is a chronic infectious parasitic disease that is fatal and still being neglected. Currently, the AE treatment recommended by the WHO is complete excision of the lesions, followed by the oral administration of albendazole (ABZ), the only effective first-line anti-AE drug, for two years. Unfortunately, complete excision of AE lesions is impossible in most cases, leaving the long-term use of ABZ as the only alternative. However, only about one-third of patients experience complete remission or cure with such treatments, largely because of the low oral bioavailability of ABZ caused by its very low solubility. To improve the oral bioavailability of ABZ, a novel nanocrystalline (NC) formulation of ABZ was obtained by spray-drying ABZ with a triblock copolymer poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (Poloxamer 188), and its physical structure was confirmed by scanning electron microscopy (SEM), small-angle X-ray scattering (SAXS), wide-angle X-ray diffraction (WAXRD), and polarized optical microscopy (POM). The significantly reduced ABZ crystallite size coupled with prolonged ABZ supersaturation significantly improved the drug dissolution performance compared with that of the commercial ABZ oral product (Albenda), and the NC formulation showed an approximately 4.2-fold higher AUC than Albenda in a pharmacokinetic comparison in Beagle dogs as measured by the plasma concentration of albendazole sulfoxide, the active antiparasitic metabolite. Even more encouragingly, after 30 days of once-daily oral administration of the NC and Albenda formulations to SD rats with hepatic alveolar echinococcosis, the NC formulation demonstrated a cyst inhibition effect 3.7-fold greater than that of Albenda. We therefore conclude that the NC formulation could potentially be developed into an improved anti-AE drug therapy.

Chitosan coated nanostructured lipid carriers for enhanced in vivo efficacy of albendazole against Trichinella spiralis

The study investigated chitosan coated nanostructured lipid carriers (NLCs) for oral delivery of albendazole in treatment of trichinellosis. NLCs comprised precirol and oleic acid with Tween and Span 80. Dicetylphosphate was used as charging agent to allow chitosan coating. Trichinella spiralis infected mice were used and albendazole suspension, coated or uncoated NLCs were orally administered at different stages of infection. NLCs were spherical with size of 188 and 200 nm for coated and uncoated NLC, respectively. Treatment during intestinal phase reduced worm count with NLCs showing better rank. This was reflected further by reduced larvae count and improved histopathological features. Starting treatment in the migrating phase reduced larval count by 62.9, 99.6 and 89.5 % after administration of suspension, coated and uncoated NLCs, respectively. The same rank was recorded for the encysted phase. NLCs enhanced the efficacy of albendazole against Trichinella spiralis compared with suspension with chitosan coated NLCs being superior.

Study on the Role of the Inclusion Complexes with 2-Hydroxypropyl-β-cyclodextrin for Oral Administration of Amiodarone

The aim of this study was to improve the solubility of amiodarone hydrochloride (AMD) and the drug release using its inclusion complexes with 2-hydroxypropyl-β-cyclodextrin (HP-β-CD). The inclusion complexes were prepared by coprecipitation and freeze-drying. The solubility enhancement of AMD/HP-β-CD inclusion complexes by 4–22 times was evaluated by the phase solubility method. The inclusion complexes were studied both in solution and in solid state by spectroscopic methods, dynamic light scattering (DLS) and zeta potential analysis, SEM, and DSC. The formulations of AMD/HP-β-CD inclusion complexes both as powdered form and as matrix tablets showed superior pharmacokinetic performance in improving loading and release properties in respect of those of the insoluble AMD drug. In vitro kinetic study reveals a complex mechanism of release occurring in three steps: the first one being attributed to a burst effect and the other two to different bonding existing in inclusion complexes. An in vivo test on matrix tablets containing Kollidon® and chitosan also reveals a multiple (at least two) peaks release diagram because of both structures of the inclusion complexes and also of different sites of absorption in biological media (digestive tract).

Enhanced Oral Bioavailability and Anti-Echinococcosis Efficacy of Albendazole Achieved by Optimizing the "Spring" and "Parachute"

Maximizing the pharmacological efficacy of albendazole (ABZ), an anti-echinococcosis drug, is essential in the long-term treatment of patients with echinococcosis. As a weakly alkaline drug, ABZ has a pH-dependent solubility that decreases dramatically from gastric fluid (pH 1.4) to intestinal fluid (pH 6.5), where it is absorbed. In this study, we endeavored to develop an optimized tablet formulation of ABZ to improve its dissolution and oral bioavailability from two aspects: a faster initial dissolution in the gastric pH condition (i.e., the "spring") and a more prolonged drug supersaturation in the intestinal pH condition (i.e., the "parachute"). To achieve this goal, ABZ-HCl salt was selected first, which demonstrated a higher intrinsic dissolution rate under pH 1.4 compared with the ABZ free base that is used in the commercial product Albenda. Second, by comparing the ABZ supersaturation kinetics under pH 6.5 in the presence of various polymers including poly(vinylpyrrolidone) (PVP), PVP/VA, hydroxypropyl methylcellulose (HPMC), and HPMC acetate succinate (HPMC-AS), HPMC-AS was found to be the most effective crystallization inhibitor for ABZ, likely due to the hydrophobic interaction between ABZ and HPMC-AS in an aqueous environment. The newly designed tablet formulation containing ABZ-HCl and HPMC-AS showed ∼3 times higher oral bioavailability compared with that of Albenda in Beagle dogs. More significantly, the anti-echinococcosis efficacy of the improved formulation was 2.4 times higher than that of Albenda in a secondary hepatic alveolar echinococcosis Sprague-Dawley rat model. The strategy of simultaneously improving the spring and parachute of an oral formulation of ABZ, by using a highly soluble salt and an effective polymeric crystallization inhibitor, was once again proven to be a viable and readily translatable approach to optimize the unsatisfactory oral medicines due to solubility and bioavailability limitations.

Synthesis and characterization of a new cyclodextrin derivative with improved properties to design oral dosage forms

This work aimed to synthesize a novel β-cyclodextrin derivative, itaconyl-β-cyclodextrin to evaluate whether albendazole inclusion complexes with the new β-cyclodextrin derivative-improved albendazole dissolution efficiency and its anthelminthic activity. The new derivative was thoroughly evaluated and characterized, and an average degree of substitution of 1.4 per cyclodextrin molecule was observed. Albendazole:itaconyl-β-cyclodextrin complexes were prepared by spray drying procedures and investigated using phase solubility diagrams, dissolution efficiency, X-ray diffraction, differential scanning calorimetry, Fourier transform infrared, scanning electronic microscopy, mass spectrometry, and nuclear magnetic resonance spectroscopy. Phase solubility diagrams and mass spectrometry studies showed that the inclusion complex was formed in an equimolar ratio. Stability constant values were 602 M^-1 in water, and 149 M^-1 in HCl 0.1 N. Nuclear magnetic resonance experiments of the inclusion complex showed correlation signals between the aromatic and propyl protons of albendazole and the itaconyl-β-cyclodextrin inner protons. The studies indicated solid structure changes of albendazole included in itaconyl-β-cyclodextrin. The maximum drug release was reached at 15 min, and the inclusion complex solubility was 88-fold higher than that of the pure drug. The in vitro anthelmintic activity assay showed that the complex was significantly more effective than pure albendazole.

Mucoadhesive Cyclodextrin-Modified Thiolated Poly(aspartic acid) as a Potential Ophthalmic Drug Delivery System

Thiolated poly(aspartic acid) is known as a good mucoadhesive polymer in aqueous ophthalmic formulations. In this paper, cyclodextrin-modified thiolated poly(aspartic acid) was synthesized for the incorporation of prednisolone, a lipophilic ophthalmic drug, in an aqueous in situ gellable mucoadhesive solution. This polymer combines the advantages of cyclodextrins and thiolated polymers. The formation of the cyclodextrin-drug complex in the gels was analyzed by X-ray powder diffraction. The ocular applicability of the polymer was characterized by means of physicochemical, rheological and drug diffusion tests. It was established that the chemical bonding of the cyclodextrin molecule did not affect the complexation of prednisolone, while the polymer solution preserved its in situ gellable and good mucoadhesive characteristics. The chemical immobilization of cyclodextrin modified the diffusion profile of prednisolone and prolonged drug release was observed. The combination of free and immobilized cyclodextrins provided the best release profile because the free complex can diffuse rapidly, while the bonded complex ensures a prolonged action.

Inclusion complex and nanoclusters of cyclodextrin to increase the solubility and efficacy of albendazole

Albendazole (ABZ), a benzimidazole widely used to control gastrointestinal parasites, is poorly soluble in water, resulting in variable and incomplete bioavailability. This has favored the appearance ABZ-resistant nematodes and, consequently, an increase in its clinical ineffectiveness. Among the pharmaceutical techniques developed to increase drug efficacy, cyclodextrins (CDs) and other polymers have been extensively used with water-insoluble pharmaceutical drugs to increase their solubility and availability. Our objective was to prepare ABZ formulations, including β-cyclodextrin (βCD) or hydroxypropyl-β-cyclodextrin (HPβCD), associated or not to the water-soluble polymer polyvinylpyrrolidone (PVP). These formulations had their solubility and anthelmintic effect both evaluated in vitro. Also, their anthelmintic efficacy was evaluated in lambs naturally infected with gastrointestinal nematodes (GIN) through the fecal egg count (FEC) reduction test. In vitro, the complex ABZ/HPβCD had higher solubility than ABZ/βCD. The addition of PVP to the complexes increased solubility and dissolution rates more effectively for ABZ/HPβCD than for ABZ/βCD. In vivo, 48 lambs naturally infected with GIN were divided into six experimental groups: control, ABZ, ABZ/βCD, ABZ/βCD-PVP, ABZ/HPβCD, and ABZ/HPβCD-PVP. Each treated animal received 10 mg/kg of body weight (based on the ABZ dose) for three consecutive days. After 10 days of the last administered dose, treatment efficacy was calculated. The efficacy values were as follows: ABZ (70.33%), ABZ/βCD (85.33%), ABZ/βCD-PVP (82.86%), ABZ/HPβCD (78.37%), and ABZ/HPβCD-PVP (43.79%). In vitro, ABZ/HPβCD and ABZ/HPβCD-PVP had high solubility and dissolution rates. In vivo, although the efficacies of ABZ/βCD, ABZ/βCD-PVP, and ABZ/HPβCD increased slightly when compared to pure ABZ, this increase was not significant (P > 0.05).

Super Aqueous Solubility of Albendazole in β-Cyclodextrin for Parenteral Application in Cancer therapy

Poor aqueous solubility of anticancer drug, albendazole (ABZ), prevents parenteral application. Here, we demonstrate how to increase the aqueous solubility of ABZ to 6- 8 mg/ml using sulfobutylether - β-cyclodextrin (SBE-β-CD) or Hydroxypropyl- β-cyclodextrin (HP- β-CD) by manipulation of complexation parameters such as the physical state of ABZ (ionized in acetic acid), the concentration of ionised ABZ, agitation time and temperature. Solubility was first examined with suspension of excess ABZ powder in cyclodextrin (CD) solutions at pH (2.3, 4.0 & 7.0), subsequently with excess ionised ABZ [ABZ] at pH. 2.3 with the determination of optimal quantity of [ABZ] use for maximal complexation. Complexation time, temperature effect, stability of formulation, with in vitro and in vivo cytotoxicity of [ABZ]-SBE-β-CD was assessed. Suspended ABZ formulation at pH 2.3 showed maximum solubilisation of 2.29 & 1.72 mg/ml, whilst excess addition of [ABZ] showed poor complexation (1.26 & 1.20 mg/ml) in SBE-β-CD & HP- β-CD, respectively. The addition of 8.0 mg/ml and 7.0 mg/ml of [ABZ] to 40% CD solutions at 25ºC showed maximum complexation with SBE-β-CD & HP- β-CD, respectively, at three days, with 2 weeks stability. [ABZ] complexed with SBE-β-CD showed potent cytotoxicity (in vitro & in vivo) in ovarian tumour cells. Hence, the current method may be used for solubilising ABZ for parenteral use.

Characterization of albendazole-randomly methylated-β-cyclodextrin inclusion complex and in vivo evaluation of its antihelmitic activity in a murine model of Trichinellosis

Albendazole is a benzimidazole carbamate extensively used in oral chemotherapy against intestinal parasites, due to its broad spectrum activity, good tolerance and low cost. However, the drug has the disadvantage of poor bioavailability due to its very low solubility in water; as a consequence, a very active area of research focuses on the development of new pharmaceutical formulations to increase its solubility, dissolution rate, and bioavailability. The primary objective of this study was to prepare randomly methylated β-cyclodextrins inclusion complexes to increase albendazole dissolution rate, in order to enhance its antiparasitic activity. This formulation therapeutic efficacy was contrasted with that of the pure drug by treating Trichinella spiralis infected mice during the intestinal phase of the parasite cycle, on days five and six post-infection. This protocol significantly decreased muscle larval burden measured in the parenteral stage on day 30 post-infection, when compared with the untreated control. Thus, it could be demonstrated that the inclusion complexes improve the in vivo therapeutic activity of albendazole.

Modified β-cyclodextrin inclusion complex to improve the physicochemical properties of albendazole. complete in vitro evaluation and characterization

The potential use of natural cyclodextrins and their synthetic derivatives have been studied extensively in pharmaceutical research and development to modify certain properties of hydrophobic drugs. The ability of these host molecules of including guest molecules within their cavities improves notably the physicochemical properties of poorly soluble drugs, such as albendazole, the first chosen drug to treat gastrointestinal helminthic infections. Thus, the aim of this work was to synthesize a beta cyclodextrin citrate derivative, to analyze its ability to form complexes with albendazole and to evaluate its solubility and dissolution rate. The synthesis progress of the cyclodextrin derivative was followed by electrospray mass spectrometry and the acid-base titration of the product. The derivative exhibited an important drug affinity. Nuclear magnetic resonance experiments demonstrated that the tail and the aromatic ring of the drug were inside the cavity of the cyclodextrin derivative. The inclusion complex was prepared by spray drying and full characterized. The drug dissolution rate displayed exceptional results, achieving 100% drug release after 20 minutes. The studies indicated that the inclusion complex with the cyclodextrin derivative improved remarkably the physicochemical properties of albendazole, being a suitable excipient to design oral dosage forms.

In vitro-in vivo correlation of the effect of supersaturation on the intestinal absorption of BCS Class 2 drugs

The aim of this study was to establish an in vitro method for evaluating the effect of supersaturation on oral absorption of poorly water-soluble drugs in vivo. Albendazole, dipyridamole, gefitinib, and ketoconazole were used as model drugs. Supersaturation of each drug was induced by diluting its stock solution by fasted state simulated intestinal fluid (FaSSIF) (solvent-shift method), then dissolution and precipitation profile of the drug was observed in vitro. The crystalline form of the precipitate was checked by differential scanning calorimetry (DSC). For comparison, control suspension was prepared by suspending a drug powder directly into FaSSIF (powder-suspending method). In vivo intestinal absorption of the drug was observed in rats by determined the plasma concentration after intraduodenal administration of drug suspensions. For all drugs, suspensions prepared by solvent-shift method showed significantly higher dissolved concentration in vitro than that prepared by powder-suspending method, clearly indicated the induction of supersaturation. DSC analysis revealed that crystalline form of the precipitate profoundly affects the extent and the duration of supersaturation. A rat in vivo study confirmed that the supersaturation of these drugs increased the fraction absorbed from the intestine, which corresponded well to the in vitro dissolution and precipitation profile of drugs except for ketoconazole. For ketoconazole, an in vivo absorption study was performed in rats pretreated with 1-aminobenzotriazole, a potent inhibitor of CYP mediated metabolism. CYP inhibition study suggested that the high luminal concentration of ketoconazole caused by supersaturation saturated the metabolic enzymes and further increased the systemic exposure of the absorbed drug. The additional effects of supersaturation on the absorption of ketoconazole are consistent with previous studies in humans under differing gastric pH conditions. In conclusion, effects of supersaturation on the intestinal absorption of poorly water-soluble drugs could be predicted from in vitro dissolution and a precipitation study. However if supersaturation affects the pharmacokinetic profiles of drugs, such as a first-pass metabolism, a combination with in vivo study should be required to evaluate its impact on oral bioavailability.

Effect of β-cyclodextrin complexation on solubility and enzymatic hydrolysis rate of icariin

Objective:

The aim of this work was to investigate the effect of β-cyclodextrin complexation on the solubility and hydrolysis rate of icariin.

Material and Methods:

The inclusion complex of icariin at the molar ratio of 1:1 was obtained by the dropping method and was characterized by differential scanning calorimetry. The solubility of icariin complex in water at 37°C was 36 times greater than that of free icariin. Enzymatic hydrolysis conditions were tested for the bioconversion of icariin by mono-factor experimental design.

Methods:

The inclusion complex of icariin at the molar ratio of 1:1 was obtained by the dropping method and was characterized by differential scanning calorimetry. The solubility of icariin complex in water at 37°C was 36 times greater than that of free icariin. Enzymatic hydrolysis conditions were tested for the bioconversion of icariin by mono-factor experimental design.

Results:

The enzymatic hydrolysis experiment showed that icariin can be transformed into baohuoside I. The optimum conditions determined were as follows: pH 5.0, 50°C, the ratio of cellulase/substrate (0.6), the concentration of icariin 20 mg/ml, and reaction time 12 h. Under these enzymatic conditions, 98.2% transforming rate of baohuoside I from icariin in inclusion complexes was obtained.

Conclusion

The aqueous solubility and enzymatic hydrolysis rate of icariin were improved owing to the inclusion complexation.

Potential of ordered mesoporous silica for oral delivery of poorly soluble drugs

The use of ordered mesoporous silica is one of the more recent and rapidly developing formulation techniques for enhancing the solubility of poorly water-soluble drugs. Their large surface area and pore volume make ordered mesoporous silica materials excellent candidates for efficient drug loading and rapid release. While this new approach offers many promising advantages, further research is still necessary to elucidate the molecular mechanisms and to improve our scientific insight into the behavior of this system. In this review, the significant developments to date are presented and research challenges highlighted. Aspects of downstream processability are discussed in view of their special bulk powder properties and unique pore architecture. Lastly, perspectives for successful oral dosage form development are presented.

Exploring flubendazole formulations for use in sheep. Pharmacokinetic evaluation of a cyclodextrin-based solution

Background

Flubendazole (FLBZ) is a poor water solubility broad-spectrum BZD methylcarbamate anthelmintic compound. Cyclodextrins (CDs) are usually used to increase aqueous solubility of poor hydrosoluble compounds. The comparative in vitro aqueous solubility of FLBZ and other BZD anthelmintics in the presence of hydroxypropyl-β-cyclodextrin (HPβCD) was evaluated in the current work. Additionally, the comparative pharmacokinetic behaviour of FLBZ (and its metabolites) administered by the intraruminal (i.r.) or intraabomasal (i.a.) routes to sheep as either an aqueous CDs-based solution or a conventional carboximethylcellulose (CMC) suspension was assessed. Drug solubility studies involving albendazole, mebendazole, oxfendazole and FLBZ were performed in an aqueous solution (pH 1.2 or 7.4) with or without HPβCD (10%, w/v). The pharmacokinetic study involved two experiments. Experiment 1: In a crossover study, sheep received either a FLBZ-CDs solution (n = 3) or a FLBZ-CMC suspension (n = 3) by the i.r. route (3.8 mg/kg). The treatment Groups were reversed after a 21-days washout period. Experiment 2: sheep (n = 4) were treated by the i.a. route with the FLBZ-CDs solution (3.8 mg/kg). Plasma and abomasal fluid samples were collected between 0 and 72 h post-treatment. Samples were analysed by HPLC.

Results

Improvement of FLBZ aqueous solubility due to CDs resulted markedly higher than that observed for mebendazole and albendazole. However, oppositely to what was expected, the absorption-related pharmacokinetic parameters did not show any marked formulation-dependant effect. After the i.a. administration of FLBZ, the AUC and the Tmax of the parent compound were significantly (P < 0.05) reduced, which is consistent with ruminal bypass.

Conclusion

The administration of FLBZ as a CDs-based solution, does not seem to achieve great practical relevance for parasite control in sheep.

Pharmaceutical applications of cyclodextrins: effects on drug permeation through biological membranes

Objectives

Cyclodextrins are useful solubilizing excipients that have gained currency in the formulator's armamentarium based on their ability to temporarily camouflage undesirable physicochemical properties. In this context cyclodextrins can increase oral bioavailability, stabilize compounds to chemical and enzymatic degradation and can affect permeability through biological membranes under certain circumstances. This latter property is examined herein as a function of the published literature as well as work completed in our laboratories.

Key findings

Cyclodextrins can increase the uptake of drugs through biological barriers if the limiting barrier component is the unstirred water layer (UWL) that exists between the membrane and bulk water. This means that cyclodextrins are most useful when they interact with lipophiles in systems where such an UWL is present and contributes significantly to the barrier properties of the membrane. Furthermore, these principles are used to direct the optimal formulation of drugs in cyclodextrins. A second related critical success factor in the formulation of cyclodextrin-based drug product is an understanding of the kinetics and thermodynamics of complexation and the need to optimize the cyclodextrin amount and drug-to-cyclodextrin ratios. Drug formulations, especially those targeting compartments associated with limited dissolution (i.e. the eye, subcutaneous space, etc.), should be carefully designed such that the thermodynamic activity of the drug in the formulation is optimal meaning that there is sufficient cyclodextrin to solubilize the drug but not more than that. Increasing the cyclodextrin concentration decreases the formulation ‘push’ and may reduce the bioavailability of the system.

Conclusions

A mechanism-based understanding of cyclodextrin complexation is essential for the appropriate formulation of contemporary drug candidates.

Development and oral bioavailability assessment of a supersaturated self-microemulsifying drug delivery system (SMEDDS) of albendazole

OBJECTIVES

Albendazole's (ABZ) poor aqueous solubility is a major determinant of its variable therapeutic response (20-50%). The purpose of this study was to develop and optimize the composition of a self-microemulsifying drug delivery system (SMEDDS) of ABZ and assess its oral pharmacokinetics in rabbits.

METHODS

A D-optimal mixture design of experiments was used to select the levels of constraints of the formulation variables. The predicted composition was optimized using four responses: dispersion performance, droplet sizes, dissolution efficiency (DE) and time for 85% drug release (t(85%)).

KEY FINDINGS

The optimal composition of the ABZ-SMEDDS formulation, with approximately 5 mg/g drug loading of ABZ, was predicted to be Cremophor EL (30% w/w), Tween 80 (15% w/w), Capmul PG-8 (10% w/w) and acidified PEG 400 (45% w/w). An increase of 63% in the relative bioavailability compared with the commercial suspension was obtained with ABZ-SMEDDS as measured by albendazole sulfoxide (ABZSO) plasma levels. The area under the curve (AUC(0-->24h)) and the peak plasma concentration (C(max)) of ABZ-SMEDDS was higher than those obtained with the commercial suspension by 56% and 52%, respectively.

CONCLUSIONS

This study demonstrates a strategy for the development of a supersaturated SMEDDS formulation of a drug with low aqueous solubility.

Structure-based in silico model profiles the binding constant of poorly soluble drugs with β-cyclodextrin

Cyclodextrin inclusion complexation technique is the key method to enhance the solubility and absorption of poorly soluble drugs in the early development stage, and thus it is essential to predict the binding constant between drug molecules and cyclodextrin. Structure-based in silico model was constructed for a data set of 86 poorly soluble drugs and used to profile the binding constant of drug-β-cyclodextrin inclusion complex. The stepwise regression was employed to select the optimum subset of the independent variables. The in silico model was built by the multiple linear regression method and validated by the residual analysis, the normal Probability-Probability plot and Williams plot. For the entire data set, the R(2) and Q(2) of the model were 0.78 and 0.67, respectively. The results indicated that the fitted model is robust, stable and satisfies all the prerequisites of the regression models. The chemical space position and important contributors were compared between selected drug molecules and organic compounds available in the literature. It was suggested that the binding behavior of drug molecules with β-CD should differ from that of the common organic compounds. Focusing on structurally diverse drugs, the in silico model can be used as an efficient tool to rapidly screen the drug-β-cyclodextrin inclusion complex stability and to rationally design the new drug delivery system of poorly soluble drugs.

Two novel ternary albendazole-cyclodextrin-polymer systems: dissolution, bioavailability and efficacy against Taenia crassiceps cysts

The effect of two water-soluble polymers: pectin and polyvinylpyrrolidone in combination with beta-cyclodextrin, on the dissolution, bioavailability and cysticidal efficacy of albendazole was evaluated using a commercial suspension as reference product. The dissolution of the albendazole-beta-cyclodextrin-pectin formulation was slow and incomplete (44.7%). No statistical differences in C(max) and AUC were found between this formulation and the reference. Also its cysticidal efficacy (33%) was similar to the reference (38%). The albendazole-beta-cyclodextrin-polyvinylpyrrolidone formulation exhibited the highest dissolution rate (78.5%) and its bioavailability was also significantly increased (2.3-fold). In addition, the cysticidal activity of this formulation (83%) was greater than a commercial suspension. Our results suggest that the ternary system of albendazole-beta-cyclodextrin-polyvinylpyrrolidone could be a potential alternative for the treatment of systemic helmintic diseases and it is worth to continue its preclinical evaluation.

Flubendazole in cystic echinococcosis therapy: pharmaco-parasitological evaluation in mice

Cystic echinococcosis (CE) caused by the parasite Echinococcus granulosus is an important public health problem worldwide. Flubendazole has shown poor in vivo efficacy against CE in humans and mice. However, flubendazole causes marked in vitro damage on E. granulosus protoscoleces. The goals of the current work were: a) to compare the plasma pharmacokinetic behaviour of flubendazole formulated as a hydroxipropyl-beta-cyclodextrin aqueous solution or as a carboxymethyl celullose suspension, both given by the oral route to mice, b) to compare flubendazole clinical efficacy in secondary CE in mice after its administration as both formulations, c) to evaluate the flubendazole-induced morphological changes in hydatid cysts recovered from infected mice treated with both drug formulations. Flubendazole administration as a solution resulted in significantly higher plasma maximum concentration (C(max)) and area under the concentration-time curve (AUC) values compared to those obtained after the flubendazole-suspension treatment. This enhanced drug availability correlated with an increased efficacy against secondary CE in mice observed for the flubendazole-solution formulation, while the suspension formulation did not reach differences with the untreated control group. Similar ultrastructural changes were observed in cysts recovered from flubendazole (both formulations) treated mice after 3, 6 and 9months of infection, although the damage extension was greater after treatment with the flubendazole-solution formulation.

Albendazole treatment in cystic echinococcosis: pharmacokinetics and clinical efficacy of two different aqueous formulations

The pharmacokinetic (PK) behaviour and clinical efficacy of albendazole (ABZ) against hydatid cysts in mice were assessed after treatment with two different ABZ pharmaceutical formulations. BalbC mice received ABZ (0.5 mg/kg) prepared either as solution or suspension (50 microg/ml) for oral administration (PK study). Blood samples were collected up to 16 h post-treatment and processed to measure ABZ/metabolites concentrations in plasma. The clinical efficacy assessment was performed in BalbC mice infected 8 months earlier with Echinococcus granulosus protoscoleces. Infected animals were allocated into three experimental treatment groups: (a) untreated control, (b) ABZ-solution treated, (c) ABZ-suspension treated. Both treated groups received ABZ (0.5 mg/kg) administered under two different therapeutic schemes: dosing every 48 h over 30 days (regimen I) or treated every 12 h during 15 days (regimen II). Experimental mice were sacrificed 12 h after treatment, and cysts were recovered, weighed and processed for transmission electron microscopy. Enhanced ABZ sulphoxide (the main ABZ metabolite) concentration profiles were measured in animals treated with the ABZ solution. Any positive clinical response was obtained after treatment every 48 h (30 days therapy). However, consistent with the observed PK results, both ABZ formulations were clinically effective in infected mice treated with a 12-h dosing interval (15 days therapy).

In situ intestinal absorption behaviors of tanshinone IIA from its inclusion complex with hydroxypropyl-beta-cyclodextrin

In this paper, the intestinal permeability of the inclusion complex of tanshinone IIA (TS IIA) with 2-hydroxypropyl-beta-cyclodextrin (HP-beta-CD) was investigated. The corresponding complexation of TS IIA-HP-beta-CD was obtained by coevaporation and characterized by differential scanning calorimetry and X-ray diffraction. The recirculation intestinal perfusion technique in rats was used to study the absorption behavior of free and complexed TS IIA. The change of concentration of TS IIA was separately calculated according to Michaelis-Menten and the Fick's equation to investigate its absorption rate-limiting step. Using the mathematical models above, it was concluded that the limit step to absorption of TS IIA was the dissolution process. Different concentrations of complexed TS IIA were administrated to three intestinal segments, with the intestinal permeability ranging from 3.16x10(-5) cm.s(-1) in the duodenum (50 microg.ml(-1)) to 4.11x10(-5) cm.s(-1) in the jejunum (100 microg.ml(-1)). With the increase of dosage of complex, TS IIA's absorption did not show saturated phenomenon, suggesting its transport mechanism in vivo might primary be passive transport. Besides, the permeability of TS IIA was not apparently influenced by the perfusion section studied, which indicated that there might not exist specific absorption site for TS IIA.

Investigation of the improved effects of 2-hydroxypropyl-beta-cyclodextrin on solubility, dissolution rate, and intestinal absorptive profile of tanshinone IIA in rats

In this paper, the effect of the chemically modified cyclodextrin [namely, 2-hydroxypropyl-beta-cyclodextrin, (HP-beta-CD)] on the aqueous solubility, dissolution rate, and intestinal permeability of the tanshinone IIA (TS) was investigated. The corresponding inclusion complex of TS-HP-beta-CD at the molar ratio of 1:1 was obtained by coevaporation. The solubility of complexed TS in water at 37+/-0.1 centi-degree was 17 times greater than that for the uncomplexed drug. The dissolution rate of TS was significantly increased by the complexation with HP-beta-CD, due to its solubilizing activity. The everted intestinal sac technique in rats was used to study the absorption behavior studies of TS and this complexation through the intestinal tissues. The permeability rates of TS across the intestinal epithelial membrane were enhanced by the formation of inclusion complex with HP-beta-CD about 89, 97 and 82 times of the uncomplexed TS in duodenum, jejunum and ileum, respectively. It was revealed that the absorption rate-limiting step of TS might be the dissolution process. The present results indicated the potential use of HP-beta-CD to improve the gastrointestinal tract absorption of TS.

Cyclodextrins as pharmaceutical solubilizers

Cyclodextrins are useful functional excipients that have enjoyed widespread attention and use. The basis for this popularity from a pharmaceutical standpoint, is the ability of these materials to interact with poorly water-soluble drugs and drug candidates resulting in an increase in their apparent water solubility. The mechanism for this solubilization is rooted in the ability of cyclodextrin to form non-covalent dynamic inclusion complexes in solution. Other solubilizing attribute may include the ability to form non-inclusion based complexes, the formation of aggregates and related domains and the ability of cyclodextrins to form and stabilize supersaturated drug solutions. The increase in solubility also can increase dissolution rate and thus improve the oral bioavailability of BCS Class II and IV materials. A number of cyclodextrin-based products have reached the market based on their ability to camouflage undesirable physicochemical properties. This review is intended to give a general background to the use of cyclodextrin as solubilizers as well as highlight kinetic and thermodynamic tools and parameters useful in the study of drug solubilization by cyclodextrins.

Complexation of tanshinone IIA with 2-hydroxypropyl-beta-cyclodextrin: effect on aqueous solubility, dissolution rate, and intestinal absorption behavior in rats

In this paper, the effect of 2-hydroxypropyl-beta-cyclodextrin (HP-beta-CD) on the aqueous solubility, dissolution rate, and intestinal permeability of the tanshinone IIA (TS IIA) was investigated. The corresponding inclusion complex of TS IIA/HP-beta-CD at the molar ratio of 1:1 was obtained by coevaporation and characterized by differential scanning calorimetry, and X-ray diffraction. The solubility of complexed TS IIA in water at 37+/-0.1 degrees C was 17 times greater than that for the uncomplexed drug. The dissolution rate of TS IIA was significantly increased by the complexation with HP-beta-CD, due to its solubilizing activity. The everted intestinal sac technique in rats was used to study the absorption behavior of TS IIA and this complexation through the intestinal tissues. The permeability rates of TS IIA across the intestinal epithelial membrane were enhanced by the formation of inclusion complex with HP-beta-CD about 5.2, 5.8 and 4.8 times of the uncomplexed TS IIA in duodenum, jejunum and ileum, respectively. It was revealed that the absorption rate-limiting step of TS IIA might be the dissolution process. The present results indicate the potential use of HP-beta-CD to improve the gastrointestinal tract absorption of TS IIA.

Preparation and evaluation of a Carbopol/HPMC-based in situ gelling ophthalmic system for puerarin

The purpose of this study was to develop a pH-triggered in situ gelling vehicle for ophthalmic delivery of puerarin. The effect of hydroxypropyl-beta-cyclodextrin (HP-beta-CD) on the aqueous solubility and in vitro corneal permeation of puerarin was also investigated. The puerarin solubility increased linearly and proportionally to the HP-beta-CD concentrations and 5% (w/v) HP-beta-CD enhanced its ocular permeability significantly. Carbopol 980NF was used as the gelling agent in combination with HPMC (Methocel E4M) which acted as a viscosity-enhancing agent. The optimum concentrations of Carbopol 980NF and HPMC E4M for the in situ gel-forming delivery systems were 0.1% (w/v) and 0.4% (w/v), respectively. When these two vehicles were combined, an in situ gel that had the appropriate gel strength and gelling capacity under physiological condition could be obtained. This combined solution could flow freely under non- physiological condition and showed the character of pseudoplastic fluid under both conditions. Both in vitro release studies and in vivo pharmacokinetics studies indicated that the combined polymer systems performed better in retaining puerarin than puerarin eye drops did. These results demonstrate that the Carbopol 980NF/HPMC E4M can be a viable alternative to conventional puerarin eye drops to enhance ocular bioavailability and patient compliance.