Enhancing Giardicidal Activity and Aqueous Solubility through the Development of "RetroABZ", a Regioisomer of Albendazole: In Vitro, In Vivo, and In Silico Studies

Parasitic diseases, including giardiasis caused by Giardia lamblia (G. lamblia), present a considerable global health burden. The limited effectiveness and adverse effects of current treatment options underscore the necessity for novel therapeutic compounds. In this study, we employed a rational design strategy to synthesize retroalbendazole (RetroABZ), aiming to address the limitations associated with albendazole, a commonly used drug for giardiasis treatment. RetroABZ exhibited enhanced in vitro activity against G. lamblia trophozoites, demonstrating nanomolar potency (IC50 = 83 nM), outperforming albendazole (189 nM). Moreover, our in vivo murine model of giardiasis displayed a strong correlation, supporting the efficacy of RetroABZ, which exhibited an eleven-fold increase in potency compared to albendazole, with median effective dose (ED50) values of 5 µg/kg and 55 µg/kg, respectively. A notable finding was RetroABZ's significantly improved water solubility (245.74 µg/mL), representing a 23-fold increase compared to albendazole, thereby offering potential opportunities for developing derivatives that effectively target invasive parasites. The molecular docking study revealed that RetroABZ displays an interaction profile with tubulin similar to albendazole, forming hydrogen bonds with Glu198 and Cys236 of the β-tubulin. Additionally, molecular dynamics studies demonstrated that RetroABZ has a greater number of hydrophobic interactions with the binding site in the β-tubulin, due to the orientation of the propylthio substituent. Consequently, RetroABZ exhibited a higher affinity compared to albendazole. Overall, our findings underscore RetroABZ's potential as a promising therapeutic candidate not only for giardiasis but also for other parasitic diseases.

Giardia duodenalis: Flavohemoglobin is involved in drug biotransformation and resistance to albendazole

Giardia duodenalis causes giardiasis, a major diarrheal disease in humans worldwide whose treatment relies mainly on metronidazole (MTZ) and albendazole (ABZ). The emergence of ABZ resistance in this parasite has prompted studies to elucidate the molecular mechanisms underlying this phenomenon. G. duodenalis trophozoites convert ABZ into its sulfoxide (ABZSO) and sulfone (ABZSOO) forms, despite lacking canonical enzymes involved in these processes, such as cytochrome P450s (CYP450s) and flavin-containing monooxygenases (FMOs). This study aims to identify the enzyme responsible for ABZ metabolism and its role in ABZ resistance in G. duodenalis. We first determined that the iron-containing cofactor heme induces higher mRNA expression levels of flavohemoglobin (gFlHb) in Giardia trophozoites. Molecular docking analyses predict favorable interactions of gFlHb with ABZ, ABZSO and ABZSOO. Spectral analyses of recombinant gFlHb in the presence of ABZ, ABZSO and ABZSOO showed high affinities for each of these compounds with Kd values of 22.7, 19.1 and 23.8 nM respectively. ABZ and ABZSO enhanced gFlHb NADH oxidase activity (turnover number 14.5 min-1), whereas LC-MS/MS analyses of the reaction products showed that gFlHb slowly oxygenates ABZ into ABZSO at a much lower rate (turnover number 0.01 min-1). Further spectroscopic analyses showed that ABZ is indirectly oxidized to ABZSO by superoxide generated from the NADH oxidase activity of gFlHb. In a similar manner, the superoxide-generating enzyme xanthine oxidase was able to produce ABZSO in the presence of xanthine and ABZ. Interestingly, we find that gFlHb mRNA expression is lower in albendazole-resistant clones compared to those that are sensitive to this drug. Furthermore, all albendazole-resistant clones transfected to overexpress gFlHb displayed higher susceptibility to the drug than the parent clones. Collectively these findings indicate a role for gFlHb in ABZ conversion to its sulfoxide and that gFlHb down-regulation acts as a passive pharmacokinetic mechanism of resistance in this parasite.

Quantitative Analysis of Abamectin, Albendazole, Levamisole HCl and Closantel in Q-DRENCH Oral Suspension Using a Stability-Indicating HPLC-DAD Method

Combination therapy of many anthelmintic drugs has been used to achieve fast animal curing. Q-DRENCH is an oral suspension, containing four different active drugs against GIT worms in sheep, commonly used in Australia and New Zeeland. The anti-parasitic drugs are Albendazole (ALB), Levamisole HCl (LEV), Abamectin (ABA), and Closantel (CLO). The main purpose of this study is to present a new simultaneous stability-indicting HPLC-DAD method for the analysis of the four drugs. The recommended liquid system was 1 mL of Triethylamine/L water, adjusting the pH to 3.5 by glacial acetic acid: acetonitrile solvent (20:80, v/v). Isocratic elusion achieved the desired results of separation at a 2 mL/min flow rate using Zorbax C-18 as a stationary phase. Detection was performed at 210 nm. The linearity ranges were 15.15 to 93.75 μg/mL for ALB, 25 to 150 μg/mL for LEV, 30 to 150 μg/mL for ABA, and 11.7 to 140.63 μg/mL for CLO. Moreover, the final greenness score was 0.62 using the AGREE tool, which reflects the eco-friendly nature. Moreover, the four drugs were determined successfully in the presence of their stressful degradation products. This work presents the first chromatographic method for simultaneous analysis for Q-DRENCH oral suspension drugs in the presence of their stressful degradation products.

Elimination of Giardia duodenalis BIV in vivo using natural extracts in microbiome and dietary supplements

In this study, a combination therapy of several natural products was evaluated in vivo in the Giardia duodenalis infection model. G. duodenalis infected mice were treated as follows: distilled water (infected control C+), BIOintestil® (BIO; natural products of Cymbopogon martinii and Zingiber officinale), MicrobiomeX® (MBX; extract of Citrus sinensis and Citrus paradisi), MBX + BIO, Camellia sinensis tea (CPR; black tea). These natural compounds were administered in a dose of 100 mg/day and were compared to G. duodenalis-infected mice treated with albendazole (ALB; 50 mg/Kg/day) and metronidazole (MET; 500 mg/Kg/day), the conventional therapies used to this day. One group remained un-infected and untreated as our control group (C-). Treatment started 8 days after infection, and after 5 days of treatment (7 days for MET), all animals were followed for 15 days. We continuously checked for the presence of G. duodenalis by Faust method, in association with detection of the parasite by PCR from feces, as well for the presence of trophozoites in the intestinal mucosa after sacrifice. Animals treated with MBX, BIO and MBX + BIO presented an undetectable parasitic load until the 15th day of monitoring, while animals treated with CPR, MET and ALB continued to release cysts. Animals in the MBX, MBX + BIO, ALB groups consumed lower feed, MBX, CPR, MET had greater weight and MBX, MBX + BIO, BIO, CPR, C- consumed more water when compared to infected-group control. MBX and BIO alone or associated eliminated G. duodenalis without apparent adverse effects and animals of these groups showed better clinical performance in relation to those with high parasitic load. MET, ALB and CPR only decreased the number of cysts, indicating limitations and therapeutic failure.

Solid Polymeric Nanoparticles of Albendazole: Synthesis, Physico-Chemical Characterization and Biological Activity

Albendazole is a benzimidazole derivative with documented antitumor activity and low toxicity to healthy cells. The major disadvantage in terms of clinical use is its low aqueous solubility which limits its bioavailability. Albendazole was incorporated into stable and homogeneous polyurethane structures with the aim of obtaining an improved drug delivery system model. Spectral and thermal analysis was used to investigate the encapsulation process and confirmed the presence of albendazole inside the nanoparticles. The in vitro anticancer properties of albendazole encapsulated in polyurethane structures versus the un-encapsulated compound were tested on two breast cancer cell lines, MCF-7 and MDA-MB-231, in terms of cellular viability and apoptosis induction. The study showed that the encapsulation process enhanced the antitumor activity of albendazole on the MCF-7 and MDA-MB-23 breast cancer lines. The cytotoxic activity manifested in a concentration-dependent manner and was accompanied by changes in cell morphology and nuclear fragmentation.

Anthelmintic Activity of Yeast Particle-Encapsulated Terpenes

Soil-transmitted nematodes (STN) infect 1-2 billion of the poorest people worldwide. Only benzimidazoles are currently used in mass drug administration, with many instances of reduced activity. Terpenes are a class of compounds with anthelmintic activity. Thymol, a natural monoterpene phenol, was used to help eradicate hookworms in the U.S. South circa 1910. However, the use of terpenes as anthelmintics was discontinued because of adverse side effects associated with high doses and premature stomach absorption. Furthermore, the dose-response activity of specific terpenes against STNs has been understudied. Here we used hollow, porous yeast particles (YPs) to efficiently encapsulate (>95%) high levels of terpenes (52% w/w) and evaluated their anthelmintic activity on hookworms (Ancylostoma ceylanicum), a rodent parasite (Nippostrongylus brasiliensis), and whipworm (Trichuris muris). We identified YP-terpenes that were effective against all three parasites. Further, YP-terpenes overcame albendazole-resistant Caenorhabditis elegans. These results demonstrate that terpenes are broad-acting anthelmintics. Terpenes are predicted to be extremely difficult for parasites to resist, and YP encapsulation provides water-suspendable terpene materials without surfactants and sustained terpene release that could lead to the development of formulations for oral delivery that overcome fast absorption in the stomach, thus reducing dosage and toxic side effects.

Antitumor Effect of Albendazole on Cutaneous Squamous Cell Carcinoma (SCC) Cells

Drug repurposing and/or repositioning is an alternative method to develop new treatment for certain diseases. Albendazole was originally developed as an anthelmintic medication, and it has been used to treat a variety of parasitic infestations. In this study, we investigated the antitumor effect of albendazole and putative action mechanism. Results showed that albendazole dramatically decreased the cell viability of SCC cell lines (SCC12 and SCC13 cells). Albendazole increased apoptosis-related signals, including cleaved caspase-3 and PARP-1 in a dose-dependent fashion. The mechanistic study showed that albendazole induced endoplasmic reticulum (ER) stress, evidenced by increase of CHOP, ATF-4, caspase-4, and caspase-12. Pretreatment with ER stress inhibitor 4-PBA attenuated albendazole-induced apoptosis of SCC cells. In addition, albendazole decreased the colony-forming ability of SCC cells, together with inhibition of Wnt/β-catenin signaling. These results indicate that albendazole shows an antitumor effect via regulation of ER stress and cancer stemness, suggesting that albendazole could be repositioned for cutaneous SCC treatment.

In Vitro Assessment of Supersaturation/Precipitation and Biological Membrane Permeation of Poorly Water-Soluble Drugs: A Case Study With Albendazole and Ketoconazole

This study aimed to elucidate the relationship between supersaturation and precipitation and the effect of a supersaturated state on drug membrane permeation. Stock solutions of albendazole (ALB) and ketoconazole (KTZ) dissolved in dimethyl sulfoxide (0.1-50 mg/mL) were diluted 100-fold with buffer solution (pH 6.8, 37°C). In the case of ALB, a supersaturated state and immediate precipitation were observed at 10 μg/mL or less and 20 μg/mL or higher, respectively. When KTZ was used, at an initial concentration of 200 μg/mL or higher, precipitation was observed, although the dissolved concentration remained at approximately 120 μg/mL for at least 30 min. These dissolved concentrations of ALB and KTZ related to approximately 10-fold and 14-fold over the saturated solubility from respective bulk powder. An in vitro permeation study implied that the rate of drug permeation across a biological membrane increased with increasing supersaturation. These results suggested favorable strategies for development of a supersaturable formulation could depend on the precipitation properties of the drug. Immediate- and controlled-release forms might be suitable for supersaturable formulations for KTZ and ALB, respectively.

Novel Findings of Anti-Filarial Drug Target and Structure-Based Virtual Screening for Drug Discovery

Lymphatic filariasis and onchocerciasis caused by filarial nematodes are important diseases leading to considerable morbidity throughout tropical countries. Diethylcarbamazine (DEC), albendazole (ALB), and ivermectin (IVM) used in massive drug administration are not highly effective in killing the long-lived adult worms, and there is demand for the development of novel macrofilaricidal drugs affecting new molecular targets. A Ca2+ binding protein, calumenin, was identified as a novel and nematode-specific drug target for filariasis, due to its involvement in fertility and cuticle development in nematodes. As sterilizing and killing effects of the adult worms are considered to be ideal profiles of new drugs, calumenin could be an eligible drug target. Indeed, the Caenorhabditis elegans mutant model of calumenin exhibited enhanced drug acceptability to both microfilaricidal drugs (ALB and IVM) even at the adult stage, proving the roles of the nematode cuticle in efficient drug entry. Molecular modeling revealed that structural features of calumenin were only conserved among nematodes (C. elegans, Brugia malayi, and Onchocerca volvulus). Structural conservation and the specificity of nematode calumenins enabled the development of drugs with good target selectivity between parasites and human hosts. Structure-based virtual screening resulted in the discovery of itraconazole (ITC), an inhibitor of sterol biosynthesis, as a nematode calumenin-targeting ligand. The inhibitory potential of ITC was tested using a nematode mutant model of calumenin.

Oxidative transformation kinetics and pathways of albendazole from reactions with manganese dioxide

Albendazole (ABZ) is a benzimidazole-based veterinary anthelmintic used extensively in the treatment of intestinal parasites. Due to its high hydrophobicity, ABZ tends to accumulate in soils and sediments in the environment. This study aims to investigate ABZ's possible degradation by manganese oxides. Minor effects from ionic strength and metal cations on ABZ degradation were observed. By contrast, decrease of pH greatly enhanced the reaction rate. Surface complexation between ABZ and MnO₂ was indicated to be the dominant control in the reaction kinetics. Suppression by the presence of co-solvents was negatively proportional to the solvent polarities (suppression from high to low: diethyl ether ～ n-butanol > ethanol > methanol > acetonitrile). Humic acid was found to cause significant inhibition due to the reductive dissolution of MnO₂. Four hydrolysis and six oxidative products were identified. ABZ and its hydrolysis products containing the propylthio side chain underwent the same oxidative transformation to form their corresponding sulfoxide compounds. Dehydrogenative coupling reaction between sulfoxide products and hydrolysis products could occur to generate dimers. All hydrolysis and oxidative products were eluted faster than ABZ in liquid chromatogram, suggesting that the spreading out of ABZ will be significantly enhanced if reacting with MnO₂.

Sorption of albendazole in sediments and soils: Isotherms and kinetics

Albendazole is a broad-spectrum anthelmintic drug effective against gastrointestinal parasites in humans and animals. Despite the fact that it has been detected in environment (water, sediment and soil), there is no information on its fate in the environment. So, in order to understand the sorption process of albendazole in environment, the sorption mechanism and kinetic properties were investigated through sorption equilibrium and sorption rate experiments. For that purpose, batch sorption of albendazole on five sediment samples and five soil samples from Croatia's region with different physico-chemical properties was investigated. Except physico-chemical properties of used environmental solid samples, the effects of various parameters such as contact time, initial concentration, ionic strength and pH on the albendazole sorption were studied. The K_d parameter from linear sorption model was determined by linear regression analysis, while the Freundlich and Langmuir sorption models were applied to describe the equilibrium isotherms. The estimated K_d values varied from 29.438 to 104.43 mLg^-1 at 0.01 M CaCl₂ and for natural pH value of albendazole solution (pH 6.6). Experimental data showed that the best agreement was obtained with the linear model (R² > 0.99), while the rate of albendazole sorption is the best described with the kinetic model of pseudo-second-order. Obtained results point to a medium or even strong sorption of albendazole for soil or sediment particles, which is particularly dependent on the proportion of organic matter, pH, copper and zinc in them.

Electrochemical Determination of Albendazole at Glassy Carbon Electrode

In this article, the electrochemical behavior on a glassy carbon electrode (GCE) was investigated and the electrochemical parameters of albendazole (ALB) were calculated. ALB effectively accumulated on the GCE surface and caused a pair of redox peaks at around 1.095 V and 1.028 V and an oxidation peak at 0.844 V (versus saturated calomel electrode) in 0.2 M phosphate buffer solution (pH 3.0). Under optimized conditions, the anodic peak current was linear to the ALB concentration the range of 1.5 × 10^-7 M to 4.0 × 10^-5 M. The regression equation was: Ipa (10^-6 A) = 0.79 [ALB] (μM) + 0.84 (R2 = 0.982). The detection limit 6.08 × 10^-8 M was obtained. The proposed method was successfully used to determine ALB content in tablet samples, with satisfactory results.

Phenolic Metabolites of Dalea ornata Affect Both Survival and Motility of the Human Pathogenic Hookworm Ancylostoma ceylanicum

Hookworms are ubiquitous human parasites, infecting nearly one billion people worldwide, and are the leading cause of anemia and malnutrition in resource-limited countries. Current drug treatments rely on the benzimidazole derivatives albendazole and mebendazole, but there is emerging resistance to these drugs. As part of a larger screening effort, using a hamster-based ex vivo assay, anthelmintic activity toward Ancylostoma ceylanicum was observed in the crude extract of aerial parts of Dalea ornata. These studies have led to the isolation and characterization of phenolic metabolites 1-10. The structures were determined by 1D and 2D NMR spectroscopy, and the absolute configuration of 1 was assigned using electronic circular dichroism data. The new compound, (2S)-8-(3-methylbut-2-en-1-yl)-6,7,4'-trihydroxyflavanone (1), was weakly active at 7.3 μM, with 17% reduction in survival of the hookworms after 5 days. The rotenoids deguelin (9) and tephrosin (10), predictably perhaps, were the most active, with complete worm mortality observed by day 4 (or earlier) at 6.3 and 6.0 μM, respectively. The effects of 1-10 on hookworm motility and on toxicity to hamster splenocytes were also explored as important measures of treatment potential.

Evaluation of the Impact of Excipients and an Albendazole Salt on Albendazole Concentrations in Upper Small Intestine Using an In Vitro Biorelevant Gastrointestinal Transfer (BioGIT) System

An in vitro biorelevant gastrointestinal transfer (BioGIT) system was assessed for its ability to mimic recently reported albendazole concentrations in human upper small intestine after administration of free base suspensions to fasted adults in absence and in presence of supersaturation promoting excipients (hydroxypropylmethylcellulose and lipid self-emulsifying vehicles). The in vitro method was also used to evaluate the likely impact of using the sulfate salt on albendazole concentrations in upper small intestine. In addition, BioGIT data were compared with equilibrium solubility data of the salt and the free base in human aspirates and biorelevant media. The BioGIT system adequately simulated the average albendazole gastrointestinal transfer process and concentrations in upper small intestine after administration of the free base suspensions to fasted adults. However, the degree of supersaturation observed in the duodenal compartment was greater than in vivo. Albendazole sulfate resulted in minimal increase of albendazole concentrations in the duodenal compartment of the BioGIT, despite improved equilibrium solubility observed in human aspirates and biorelevant media, indicating that the use of a salt is unlikely to lead to any significant oral absorption advantage for albendazole.

A novel hot-melt extrusion formulation of albendazole for increasing dissolution properties

The main aim of the research focused on the production of hot-melt extrusion (HME) formulations with increased dissolution properties of albendazole (ABZ). Therefore, HME was applied as a continuous manufacturing technique to produce amorphous solid dispersions of the poorly water soluble drug ABZ combined with the polymer matrix polyvinylpyrrolidone PVP K12. HME formulations of ABZ-PVP K12 comprised a drug content of 1%, 5% and 10% w/w. The main analytical characterisation techniques used were scanning electron microscopy (SEM), micro-computed tomography (μ-CT), X-ray powder diffraction (XRPD), differential scanning calorimetry (DSC) and dissolution profile studies. The application of SEM, XRPD and DSC evidenced drug physical transformation from crystalline to amorphous state and therefore, the achievement of an amorphous solid dispersion. The introduction of a novel technique, μ-CT, to characterise the internal structure of these materials revealed key information regarding materials distribution and void content. Dissolution profile studies evidenced a high increase in drug release profile compared to pure ABZ. These promising results can lead to a great enhancement of the oral bioavailability of ABZ dosage forms. Therefore, HME is a potential continuous manufacturing technique to overcome ABZ poor solubility properties and lead to a significant increase in the therapeutic effect.

Assessment of Efficacy and Quality of Two Albendazole Brands Commonly Used against Soil-Transmitted Helminth Infections in School Children in Jimma Town, Ethiopia

Background

There is a worldwide upscale in mass drug administration (MDA) programs to control the morbidity caused by soil-transmitted helminths (STHs): Ascaris lumbricoides, Trichuris trichiura and hookworm. Although anthelminthic drugs which are used for MDA are supplied by two pharmaceutical companies through donation, there is a wide range of brands available on local markets for which the efficacy against STHs and quality remain poorly explored. In the present study, we evaluated the drug efficacy and quality of two albendazole brands (Bendex and Ovis) available on the local market in Ethiopia.

Methodology/Principal Findings

A randomized clinical trial was conducted according to the World Health Organization (WHO) guidelines to assess drug efficacy, by means of egg reduction rate (ERR), of Bendex and Ovis against STH infections in school children in Jimma, Ethiopia. In addition, the chemical and physicochemical quality of the drugs was assessed according to the United States and European Pharmacopoeia, encompassing mass uniformity of the tablets, amount of active compound and dissolution profile. Both drugs were highly efficacious against A. lumbricoides (>97%), but showed poor efficacy against T. trichiura (~20%). For hookworms, Ovis was significantly (p < 0.05) more efficacious compared to Bendex (98.1% vs. 88.7%). Assessment of the physicochemical quality of the drugs revealed a significant difference in dissolution profile, with Bendex having a slower dissolution than Ovis.

Conclusion/Significance

The study revealed that differences in efficacy between the two brands of albendazole (ABZ) tablets against hookworm are linked to the differences in the in-vitro drug release profile. Differences in uptake and metabolism of this benzimidazole drug among different helminth species may explain that this efficacy difference was only observed in hookworms and not in the two other species. The results of the present study underscore the importance of assessing the chemical and physicochemical quality of drugs before conducting efficacy assessment in any clinical trials to ensure appropriate therapeutic efficacy and to exclude poor drug quality as a factor of reduced drug efficacy other than anthelminthic resistance. Overall, this paper demonstrates that “all medicines are not created equal”.

Soil-transmitted helminths (STHs) infect millions of children worldwide. To fight STH, large-scale de-worming programs are implemented in which anthelmintic drugs (either albendazole (ABZ) or mebendazole (MEB)) are administered. However, there is a wide range of other brands, which are even more accessible, but for which the efficacy and quality remain poorly explored. We evaluated efficacy against STHs and quality of two ABZ brands commonly available on the local markets in Ethiopia (Bendex and Ovis). Both brands showed high efficacy against roundworm infections and poor efficacy against whipworms. However, for hookworm infections, Bendex was significantly less efficacious than Ovis. In terms of drug quality, a significant difference was observed in the dissolution profile, with Bendex having a significantly slower dissolution rate than Ovis. Since dissolution behavior is critical for a drug to be appropriately absorbed into the helminth (through host-blood and/or parasite-cuticle) and produce therapeutic efficacy, the poor dissolution of Bendex compared to Ovis can explain the observed difference in efficacy against hookworms. Our results emphasize the importance of periodically assessing of drug quality to ensure appropriate therapeutic efficacy and to exclude poor drug quality as a potential factor of reduced drug efficacy other than drug resistance.

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.

Biotransformation of benzimidazole anthelmintics in reed (Phragmites australis) as a potential tool for their detoxification in environment

Benzimidazole anthelmintics, the drugs against parasitic worms, are widely used in human as well as veterinary medicine. Following excretion, these substances may persist in the environment and impact non-target organisms. In order to test phytoremediation as a possible tool for detoxification of anthelmintics in environment, the biotransformation pathways of albendazole (ABZ) and flubendazole (FLU) were studied in reed (Phragmites australis) in vitro. Reed cells were able to uptake and biotransform both anthelmintics. Ten ABZ metabolites and five FLU metabolites were found. Some atypical biotransformation reactions (formation of glucosylglucosides, acetylglucosides and xylosylglucosides), which have not been described previously, were identified. Based on the obtained results, the schemes of metabolic pathways of ABZ and FLU in reed were proposed. Most of ABZ and FLU metabolites can be considered as anthelmintically less active; therefore uptake and biotransformation of these anthelmintics by reed could be useful for decrease of their toxicity in environment.

Salt screening and characterization for poorly soluble, weak basic compounds: case study albendazole

In preclinical development, salt forms are often screened to assess their ability to improve drug candidate properties. In this study albendazole was used as a model for poorly soluble, weak basic compounds typical of current drug discovery programs. Four salts, the hydrochloride, mesylate, sulfate und tosylate, were prepared and characterized with respect to their physicochemical properties. Identity was confirmed by 1H NMR spectroscopy, ion chromatography and vibrational spectroscopy. The solid state forms of the albendazole salts were examined by scanning electron microscopy (SEM), X-ray powder diffraction (XRPD), laser diffraction measurement of particle size distribution (PSD), B.E.T. measurement of the specific surface area and 13C solid state NMR spectroscopy. Thermal behaviour and hygroscopicity were assessed by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), dynamic vapour sorption (DVS), Karl Fischer titration (KFT) and by variable temperature XRPD. Additionally, solubility and dissolution experiments were carried out in water and buffers. The different salt forms show pronounced differences in their physicochemical behaviour, especially with respect to hygroscopicity (sulfate > hydrochloride > tosylate > mesylate) and dissolution (rank order is pH dependent, all better than the free base). A salt form with highly improved physicochemical properties, the mesylate, was identified. The results demonstrate that extensive physicochemical characterization is needed to select the salt form most appropriate for further pharmaceutical development.

Complexation of albendazole with hydroxypropyl-β-cyclodextrin significantly improves its pharmacokinetic profile, cell cytotoxicity and antitumor efficacy in nude mice

BACKGROUND

Albendazole (ABZ) is a microtubule depolymerizing agent with a remarkable activity against a variety of tumor cells in vitro and in vivo. However, the lack of water solubility limits its application. Therefore, the aim of this study was to formulate ABZ with acetic acid/2-hydroxypropyl-β-cyclodextrin (HPβCD) with the view of improving its aqueous solubility and therefore, its antitumor efficacy.

MATERIALS AND METHODS

ABZ was dissolved in acetic acid and 25% HPβCD (w/v). Mice received a single dose of ABZ/HPβCD or a conventional suspension in hydroxypropyl methyl cellulose (HPMC) over 24 h and the concentration of ABZ and its metabolites in plasma were measured by HPLC. The antitumor efficacy of the two formulations were then evaluated and compared in nude mice bearing HCT-116 colorectal cancer xenografts.

RESULTS

Ionization with acetic acid together with complexation with hydroxylpropyl-β-cyclodextrin (HPβCD) dramatically improved the solubility of ABZ. The area under the curve (AUC) of ABZ and its active metabolite, ABZ sulfoxide (ABZSO) were approximately 2.3- and 7.3-folds higher in mice that received ABZ/HPβCD in comparison with animals that were treated with ABZ/HPMC. Additionally, the peak plasma concentration (C(max)) of ABZSO was nearly 18-times higher in mice that received ABZ/HPβCD. Furthermore, a significant delay in tumor growth that led to longer survival in mice was observed in the ABZ/HPβCD-treated group as compared to the ABZ/HPMC group.

CONCLUSION

These findings demonstrate that the combination of acetic acid and HPβCD significantly improves the solubility, pharmacokinetic profile and antitumor efficacy of ABZ. This newly-developed formulation of ABZ may be suitable for parenteral administration.

Spectroscopic and spectrofluorimetric studies on the interaction of albendazole and trimethoprim with iodine

Raman, UV-vis, FT-IR, and fluorescence spectral techniques were employed to investigate the mechanism of interaction of albendazole (ALB) and trimethoprim (TMP) drugs with iodine. Interactions of ALB and TMP with iodine yields triiodide ion and its formation was confirmed by electronic and Raman spectra. The peaks appeared in Raman spectra of the isolated products are at around 145, 113 and 82 cm(-1) are assigned to ν(as)(I-I), ν(s)(I-I) and δ(I(3)(-)) respectively, confirmed the presence of I(3)(-) ion. Formation constant (K), molar extinction coefficient (ɛ) and thermodynamic properties ΔH(#), ΔS(#) and ΔG(#) were determined and discussed. Fluorescence quenching studies indicated that the interaction between the ALB, TMP with iodine are spontaneous and the TMP-iodine interaction is found to be stronger than that the other system. Solvent variation studies indicated that the binding constant increased with an increase in polarity of the medium.

Spectroscopic investigation on the mechanism of formation of molecular complexes of albendazole and trimethoprim with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone

UV-vis, (1)H NMR, FT-IR, mass and fluorescence spectral techniques were employed to investigate the mechanism of interaction of albendazole and trimethoprim with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) and to characterize the reaction products. The interaction of DDQ with trimethoprim (TMP) and albenadazole (ALB) were found to proceed through the formation of donor-acceptor complex, containing DDQ radical anion and its conversion to the product. Fluorescence quenching studies indicated that the interaction between the donors and the acceptor are spontaneous and the interaction of TMP-DDQ (binding constant=2.9×10(5)) is found to be stronger than that the ALB-DDQ (binding constant=3×10(3)) system. Also, the binding constant increased with an increase in polarity of the medium indicating the involvement of radical anion as intermediate.

Development of a method to determine albendazole and its metabolites in the muscle tissue of yellow perch using high-performance liquid chromatography with fluorescence detection

An HPLC method was developed for the determination of albendazole (ABZ) and its metabolites, a sulfoxide (ABZSO), a sulfone (ABZSO2), and albendazole-2-aminosulfone (ABZ-2-NH2SO2), from yellow perch muscle tissue with adhering skin. The muscle tissue samples were made alkaline with potassium carbonate and extracted with ethyl acetate, followed by a series of liquid-liquid extraction steps. After solvent evaporation, the residue was reconstituted in the initial mobile phase combination of the gradient. The mobile phase consisted of a buffer, 50 mM ammonium acetate (pH = 4.0) in 10% methanol-water, and 100% acetonitrile. The gradient was from 20% acetonitrile to 85% acetonitrile. The analytes were chromatographed on an RP Luna C18(2) column and detected by fluorescence with excitation and emission wavelengths of 290 and 330 nm, respectively. The average recoveries from fortified muscle tissue for ABZ (20-100 ppb), ABZ-SO (20-200 ppb), ABZSO2 (8-100 ppb), and ABZ-2-NH2SO2 (20-100 ppb) were 85, 95, 101, and 86%, respectively, with corresponding CV values of 9, 3, 6, and 4%, respectively. Their LOQ values were 10, 10, 1, and 10 ppb, respectively. The procedure was applied to determine ABZ and its major metabolites in the incurred muscle tissue of yellow perch obtained after orally dosing the fish with ABZ.

Spectral, thermal, kinetic, molecular modeling and eukaryotic DNA degradation studies for a new series of albendazole (HABZ) complexes

This work represents the elaborated investigation for the ligational behavior of the albendazole ligand through its coordination with, Cu(II), Mn(II), Ni(II), Co(II) and Cr(III) ions. Elemental analysis, molar conductance, magnetic moment, spectral studies (IR, UV-Vis and ESR) and thermogravimetric analysis (TG and DTG) have been used to characterize the isolated complexes. A deliberate comparison for the IR spectra reveals that the ligand coordinated with all mentioned metal ions by the same manner as a neutral bidentate through carbonyl of ester moiety and NH groups. The proposed chelation form for such complexes is expected through out the preparation conditions in a relatively acidic medium. The powder XRD study reflects the amorphous nature for the investigated complexes except Mn(II). The conductivity measurements reflect the non-electrolytic feature for all complexes. In comparing with the constants for the magnetic measurements as well as the electronic spectral data, the octahedral structure was proposed strongly for Cr(III) and Ni(II), the tetrahedral for Co(II) and Mn(II) complexes but the square-pyramidal for the Cu(II) one. The thermogravimetric analysis confirms the presence or absence of water molecules by any type of attachments. Also, the kinetic parameters are estimated from DTG and TG curves. ESR spectrum data for Cu(II) solid complex confirms the square-pyramidal state is the most fitted one for the coordinated structure. The albendazole ligand and its complexes are biologically investigated against two bacteria as well as their effective effect on degradation of calf thymus DNA.

Improved albendazole dissolution rate in pluronic 188 solid dispersions

Solids dispersions (SDs) have been proposed as an alternative to improve the dissolution rate of low solubility drugs. SDs containing albendazole (ABZ; 5, 10, 25, and 50% w/w) and Pluronic 188 (P 188) as hydrophilic carrier were formulated. The obtained SDs were assessed in comparison to physical mixtures (PMs). Drug-polymer interactions in solid state were investigated using Fourier-transform infrared spectroscopy, scanning electron microscopy, and X-ray diffraction analysis. No chemical interaction was found between ABZ and poloxamer. The dissolution profiles indicated that ABZ incorporated in SDs and PMs was rapidly released, reaching rapidly the steady state. Increased dissolution rates are usually observed at the highest polymer proportions. However, an opposite effect for SDs as well as for PMs was observed in the assays described here. The systems with the lowest P 188 percentages (SD4, SD3; PM4, PM3) tended to be more effective in increasing the ABZ dissolution rate. Such a result can be attributed to the fact that concentrated aqueous solutions of Poloxamer may form thermo-reversible gels. The physical-mechanical properties indicated that SDs possess improved flow and compacting properties compared to PMs. Thus, ABZ SDs would be more convenient for solid dosage form design and manufacture.

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.

[In vitro observation on albendazole sulfoxide and its enantiomers against Echinococcus granulosus protoscolex]

OBJECTIVE

To investigate in vitro anti-hydatid efficacy on Echinococcus granulosus protoscolex (EgPSC) by using albendazole sulfoxide (ASOX) and its two enantiomeric antipodes, L-ASOX and D-ASOX.

METHODS

Eg protoscoleces were divided into eight groups and cultured in the DMEM culture media under two concentrations(50 microg/ml and 100 microg/ml) of ASOX, L-ASOX and D-ASOX respectively. The appropriate controls included (i) a culture containing an equal amount of DMSO and (ii) a culture medium alone. The mortality of EgPSC in each group was daily counted until 100% EgPSC death in some groups.

RESULTS

Significant difference of EgPSC mortality was found among the three drugs with various concentrations compared to control group (P < 0.01), and a significant difference between L-ASOX group and D-ASOX group (P < 0.05). There were no statistical difference between ASOX group and D-ASOX group (P > 0.05), but between ASOX group and L-ASOX group (P < 0.05). On the 9th day of culture, the mortality of protoscoleces with the concentration of 50 microg/ml was 93.6%, 56.2% and 99.0% in ASOX, L-ASOX and D-ASOX groups respectively, and those under the concentration of 100 microg/ml were 100%, 74.5% and 100% respectively. The mortality was 19.1% and 22.5% respectively in the control and solvent groups.

CONCLUSION

ASOX, L-ASOX and D-ASOX demonstrate significant effect of anti- Eg protoscolex in vitro. D-ASOX shows stronger effect than L-ASOX.

Albendazole-cyclodextrin complex: enhanced cytotoxicity in ovarian cancer cells

BACKGROUND

Over recent years, we have identified a potentially new indication for albendazole (ABZ) namely that of an anticancer agent. Our recent data indicate that besides regional use, the drug is quite likely to be useful as a systemic anticancer agent. However, with extremely low solubility, ABZ has to be prepared in a biocompatible solubilized form before any systemic evaluation is possible. The present study aimed at preparing soluble ABZ and evaluating its in vitro antiproliferative efficacy and toxicity.

EXPERIMENTAL DESIGN

Using beta-cyclodextrins (CDs), various formulations of ABZ were prepared and tested in cell culture for antiproliferative efficacy, cell integrity and cell toxicity against human ovarian cancer cell lines 1A9, OVCAR-3 and SKOV-3. Hepatocytes isolated from patients undergoing liver tumor resection were used for toxicity evaluations.

RESULTS

Treatment of tumor cells with ABZ-CD + citric acid (CA) solution led to dose-dependent inhibition of cell proliferation. Compared to an ethanolic solution of ABZ, ABZ-CD + CA increased the antiproliferative efficacy of ABZ. Furthermore, in contrast to the ethanolic solution, ABZ-CD-CA complex profoundly (p<0.001) reduced the number of OVCAR-3 colonies formed. Fresh human hepatocytes exposed for 3 days to the highest ABZ concentration used in the study (1 microM), revealed no drug toxicity.

CONCLUSION

Complexation of ABZ with beta-cyclodextrin leads to the formation of an ABZ solution with potent antiproliferative effects. This solution may find clinical value as an intravenous anticancer agent.

Membrane-water partitioning, membrane permeability, and baseline toxicity of the parasiticides ivermectin, albendazole, and morantel

A comparative hazard assessment of the antiparasitics ivermectin, albendazole, and morantel was performed, with a particular focus on bioavailability and uptake into biological membranes. The experimentally determined liposome-water distribution ratio at pH 7 (D(lipw) (pH 7)) of the positively charged morantel was 100 L/kg lipid. The D(lipw) (pH 7) of albendazole was 3,000 L/kg lipid. The membrane permeability determined with the parallel artificial membrane permeability assay was consistent with predictions from a quantitative structure-activity relationship (QSAR) for morantel but 14-fold lower than predicted for albendazole, which can be rationalized because neutral albendazole is, in fact, zwitterionic and the large dipole moment hinders permeation through hydrophobic membranes. An unusually large molecule, ivermectin was suspected to show decreased bioaccumulation because of its bulkiness, but experimental determination of solubility showed that it was 40-fold less soluble than expected from a QSAR between solubility and the octanol-water partition coefficient. In contrast, its membrane permeability appeared to be typical for a compound of the given hydrophobicity, but it was not possible to determine the membrane-water partition coefficient because of its low solubility and high affinity to the dialysis membrane of the experimental device. The D(lipw) (pH 7) for ivermectin of 2,700 L/kg lipid was calculated with a QSAR model. Morantel and albendazole were baseline toxicants in the bioluminescence inhibition test with Vibrio fischeri and a test for inhibition of photosynthesis in green algae. Only ivermectin exhibited a specific effect toward algae, but the excess toxicity was not very pronounced and might be biased by the uncertainty of the estimated hydrophobicity descriptor. Overall, we did not find any unexpected effect on nontarget endpoints.

Room temperature ionic liquids and their mixtures: potential pharmaceutical solvents

Room temperature ionic liquids (RTILs) are organic salts which are liquids at ambient temperature. Composed of relatively large asymmetric organic cations and inorganic or organic anions, they have generated interest as 'green' solvents. Here we report on the solvency of alkyl imidazolium salts (PF(6)(-)Br(-)Cl(-)) for poorly water-soluble model drugs, albendazole and danazol, indicating their potential application as pharmaceutical solvents/cosolvents. The solubility of albendazole, for example, is increased by more than 10,000 times by 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim]PF(6)(-)). Ionic liquids can be water-miscible or water-immiscible. The aqueous miscibility of a poorly water-miscible RTIL such as of [bmim]PF(6)(-) can be improved by the inclusion of a second more miscible RTIL (e.g. 1-hexyl-3-methylimidazolium bromide ([hmim]Br(-))). The extent of improvement in water miscibility was found to correlate with the hydrophilicity of the second RTIL. This ability to modulate RTILs' aqueous miscibility increases their usefulness as pharmaceutical solvents.

Comparative plasma disposition of fenbendazole, oxfendazole and albendazole in dogs

The plasma disposition of fenbendazole (FBZ), oxfendazole (OFZ) and albendazole (ABZ); and the enantiospecific disposition of OFZ, and ABZSO produced were investigated following an oral administration (50 mg/kg) in dogs. Blood samples were collected from 1 to 120 h post-administration. The plasma samples were analysed by high performance liquid chromatography (HPLC). The plasma concentration of FBZ, OFZ, ABZ and their metabolites were significantly different from each other and depended on the drug administered. The sulphone metabolite (FBZSO2) of FBZ was not detected in any plasma samples and the parent molecule ABZ did not reach quantifiable concentrations following FBZ and ABZ administration, respectively. OFZ and its sulphone metabolite attained a significantly higher plasma concentration and remained much longer in plasma compared with FBZ and ABZ and their respective metabolites. The maximum plasma concentrations (Cmax), area under the concentration time curve (AUC) and mean residence time (MRT) of parent OFZ were more than 30, 68 and 2 times those of FBZ, respectively. The same parameters for ABZSO were also significantly greater than those of FBZSO. The ratio for total AUCs of both the parent drug and the metabolites were 1:42:7 for following FBZ, OFZ and ABZ administration, respectively. The enantiomers were never in racemic proportions and (+) enantiomers of both OFZ and ABZSO were predominant in plasma. The AUC of (+) enantiomers of OFZ and ABZSO was, respectively more than three and seven times larger than that of (-) enantiomers of both molecules. It is concluded that the plasma concentration of OFZ was substantially greater compared with FBZ and ABZ. The data on the pharmacokinetic profile of OFZ presented here may contribute to evaluate its potential as an anthelmintic drug for parasite control in dogs.

Pharmacokinetics of albendazole sulfoxide enantiomers administered in racemic form and separately in rats

The pharmacokinetic behaviour of albendazole sulfoxide (ABZSO) enantiomers was studied in rats after the oral administration of 10 mg/kg of rac-ABZSO, 5 mg/kg of (-)-ABZSO or 5 mg/kg of (+)-ABZSO. The disposition profiles of ABZSO enantiomers were similar in all treatments, but the calculated area under the curve for the (-)-ABZSO was higher in all cases compared with (+)-ABZSO. The results suggest that there is no chiral inversion of ABZSO enantiomers. After the administration of rac-ABZSO, 17.2% of the total dose was recovered in urine as albendazole ABZ (0.1%), albendazole sulfone ABZSO(2) (0.3%), albendazole 2-aminosulfone (ABZ-SO(2)NH(2)) (3.1%) and ABZSO (13.7%). The ratio (+) to (-) was similar in urine (1.6) and blood (1.7).

Mouflon (Ovis musimon) dicrocoeliosis: Effects of parasitosis on the activities of biotransformation enzymes and albendazole metabolism in liver

Parasitic infections can modify the host's ability to metabolize drugs and other xenobiotics by altering the biotransformation enzymes; these changes may have various pharmacological, toxicological or physiological consequences. In our study, several activities of liver biotransformation enzymes and in vitro metabolism of albendazole (ABZ) were tested and compared in non-infected mouflons (Ovis musimon) and in mouflons infected by lancet fluke (Dicrocoelium dendriticum). Subcellular fractions of liver homogenates were isolated from 5+5 mouflon rams (1-year-old) parasitologically negative or naturally infected by fluke. From the eight enzyme activities that were assayed, only two activities significantly differ in the case of Dicrocoelium-infected versus non-infected animals. In infected mouflons, a significant increase (53%) of thiobenzamide-S-oxidase (TBSO) activity, corresponding mainly to the activity of flavine monooxygenase (FMO), and significant decrease (60%) of glutathione-S-transferase (GST) activity was observed. In addition, dicrocoeliosis caused the enhancement of ABZ hepatic biotransformation. The velocity of the formation of (+)-ABZ sulfoxide and ABZ sulfone was significantly increased. However, the shifts in ABZ biotransformation were very mild that undesirable alterations in ABZ pharmacokinetic are not expected. From this point of view, the use of ABZ in the therapy of mouflon dicrocoeliosis in young animals can be recommended. The treatment of the same mouflons by other drugs that are mainly conjugated with glutathione, seems to be more problematic; hence, all consequences of documented reduced GST activity should be accounted.

Inhibition of albendazole crystallization in poly(vinylpyrrolidone) solid molecular dispersions

The main aim of the study was to investigate the mechanisms of the stabilizing effect of poly(vinylpyrrolidone) (PVP) on amorphous albendazole (ABZ). Solid dispersions of ABZ with PVP polymers and with a copolymer containing poly(vinylacetate) (PVP/VA) were prepared using the solvent casting method. The effects of PVP molecular weight, composition and content on the crystallization of ABZ from the amorphous state were investigated using differential scanning calorimetry. Stability of the amorphous drug with respect to isothermal crystallization was studied at different polymer concentrations and storage temperatures. Solid dispersions were found to be X-ray amorphous and exhibited a single glass transition temperature (Tg). Onset of crystallization and extent of inhibition increased with concentration and molecular weight of the homopolymer. In spite of its having a higher molecular weight, replacement of about 40% of vinylpyrrolidone monomers with vinylacetate groups (as in the copolymer) resulted in reduced inhibition of crystallization. ABZ crystallized from the amorphous state in the absence of polymer even when stored below the Tg. The solvent casting method greatly reduced the requirement for polymer to achieve X-ray amorphous solid dispersions. Such dispersions exhibited a significant increase in induction time and reduction in the rate of crystallization at polymer concentrations as low as 5% and at temperatures as high as 70 degrees C. Factors other than mobility, such as drug-polymer hydrogen bonding' were also found to be involved in crystallization inhibition.

An in vitro kinetic method for detection of precipitation of poorly soluble drugs

A simple in vitro method for the detection of precipitation using 96-well microplates and a SpectraMax Plus microtiter plate reader has been developed and described. The method requires only small amount of drug and is, therefore, potentially applicable in early pre-formulation. The method is based on opacity changes that occur with precipitation and yields several descriptive parameters, onset time (Tonset), maximum rate (Vmax) and the time to reach Vmax (Tmax). Using these parameters, potential parenteral formulations can be ranked by their tendency to precipitate on dilution. We report use of this method and ranking of potential formulations of ricobendazole (RBZ), a poorly soluble anthelmintic, in various solvent systems. Detection at 500 nm was more sensitive than a wavelength of 550 nm and increased temperature (37 degrees C compared with 25 degrees C) accelerated precipitation. Results demonstrated the method was simple, descriptive and objective in the detection of precipitation of ricobendazole formulation on dilution and pH shift.

The use of an in vitro dissolution and absorption system to evaluate oral absorption of two weak bases in pH-independent controlled-release formulations

The aim of this study was to compare the oral absorption of two weak bases including their pH-independent controlled-release preparations using an in vitro evaluation system. This system is able to simulate dissolution of drugs, pH change and permeation of drugs through the epithelial cell membrane in the gastrointestinal tract. Albendazole-polymers solid dispersion and pH-independent sustained-release granules of dipyridamole were prepared by using a solvent method. Elution profiles and predicted absorption of these preparations in gastric pH conditions similar to those in healthy subjects and patients with achlorhydria were compared with those of a physical mixture and commercial tablets. When a physical mixture or commercial tablets were used, the elution profile and predicted absorption of both albendazole and dipyridamole were extremely pH-dependent. On the other hand, when a solid dispersion and granules were used, elution and predicted absorption were not affected by changes in pH of the flowing solution in a drug-dissolving vessel. These results are in agreement with the results of our previous in vivo study using gastric acidity-controlled rabbits. Our results suggest that this in vitro system is useful for the evaluation of oral absorption of pH-independent controlled-release preparations.

Study of electrochemical oxidation and determination of albendazole using a glassy carbon-rotating disk electrode

In this work, electrochemical oxidation of albendazole (ABZ) was carried out using a glassy carbon-rotating disk electrode. Development of electroanalytical methodology for ABZ quantification in pharmaceutical formulations was also proposed by using linear sweep voltammetric technique. Electrochemical oxidation is observed for ABZ at E(1/2)=0.99 V vs. Ag/AgCl(sat), when an anodic wave is observed. Kinetic parameters obtained for ABZ oxidation exhibited a standard heterogeneous rate constant for the electrodic process equal to (1.51+/-0.07) x 10(-5) cm s(-1), with a alphan(a) value equal to 0.76. Limiting current dependence against ABZ concentration exhibited linearity on 5.0 x 10(-5) to 1.0 x 10(-2) mol l(-1) range, being obtained a detection limit of 2.4 x 10(-5) mol l(-1). Proposed methodology was applied to ABZ quantification in pharmaceutical formulations.

Liver microsomal biotransformation of albendazole in deer, cattle, sheep and pig and some related wild breeds

Albendazole (ABZ) biotransformation was studied in vitro in liver microsomes of adult noncastrated male farm animals (ram, buck, bull and boar), castrated adult males (wether, billy and hog), and free living males (fallow buck, red deer stag, mouflon ram, roe buck and wild boar). Liver microsomal fractions were incubated with either ABZ or racemic albendazole sulphoxide (ABZSO). ABZ was extensively metabolized to the (+) and (-) enantiomers of ABZSO, whereas ABZSO underwent a slow oxidation to albendazole sulphone (ABZSO2) in all species. In all species both ABZSO enantiomers were detected. The chiral ratio, (+)-ABZSO/(-)-ABZSO, was greater than one in farm animals, mouflon and wild boar, and less than one in three species of deer. For total ABZ sulphoxidation, deer like species had lower values compared to the other species. Mouflon ram and ram had lower total sulphoxidation rates compared to wethers, as well as ABZ suphoxidation towards (+)-ABZSO. No significant difference occurred comparing ABZSO formation in mouflon ram and ram, but ABZSO2 formation rate in mouflon ram was higher than in rams and wethers. Roe deer stag, fallow buck and red deer stag did not differ in both total-ABZSO and (-)-ABZSO synthesis rates and roe deer stag and fallow buck did not differ in synthesis rates of (+)-ABZSO and ABZSO2. The bull differed from other species in all metabolites studied, except for red deer stag and boar in (-)-ABZSO synthesis rate. The extent of ABZSO sulphonation to ABZSO2 in bull microsomes was more than twice that of other species.

Physicochemical Characterization of Ricobendazole: I. Solubility, Lipophilicity, and Ionization Characteristics

The physicochemical properties of ricobendazole (RBZ) were characterized using conventional methods. Solubility in some pharmaceutical solvents, pH-solubility, ionization properties, and lipophilicity are described. The solubility of RBZ in water is 62 mug/mL and very poor in common pharmaceutical solvents, for example, oils (<0.25 mg/mL in all the tested oils) or ethanol (1.2 mg/mL) and propylene glycol (2.6 mg/mL), and slightly higher in dipolar solvents, DMSO (16.5 mg/mL). U-shaped pH-solubility profile in aqueous solutions indicates RBZ is an ampholyte. pK(a) values measured by absorbance spectroscopy and pH solubility methods were 3.45 and 3.76 for the basic group and 9.82 and 9.53 for the non-basic nitrogen, respectively. Combination of low pH and surfactant/co-solvent mixtures also improved solubility. RBZ formed a 1:1 complex with hydroxypropyl-beta-cyclodextrin (HP-beta-CD) with a binding constant (K(1:1)) of 311/M1. Apparent partition coefficients of RBZ were 14.3-15.2 at pH 6-9 and reduced at higher or lower pH. In conclusion, traditional organic co-solvents, pH-adjustment or complexation (with HP-beta-CD) approaches are unlikely to yield sufficient solubility for formulation of RBZ solutions for subcutaneous injection and novel approaches should be considered.

A possible model of benzimidazole binding to beta-tubulin disclosed by invoking an inter-domain movement

Although it is well established that benzimidazole (BZMs) compounds exert their therapeutic effects through binding to helminth beta-tubulin and thus disrupting microtubule-based processes in the parasites, the precise location of the benzimidazole-binding site on the beta-tubulin molecule has yet to be determined. In the present study, we have used previous experimental data as cues to help identify this site. Firstly, benzimidazole resistance has been correlated with a phenylalanine-to-tyrosine substitution at position 200 of Haemonchus contortus beta-tubulin isotype-I. Secondly, site-directed mutagenesis studies, using fungi, have shown that other residues in this region of the protein can influence the interaction of benzimidazoles with beta-tubulin. However, the atomic structure of the alphabeta-tubulin dimer shows that residue 200 and the other implicated residues are buried within the protein. This poses the question: how might benzimidazoles interact with these apparently inaccessible residues? In the present study, we present a mechanism by which those residues generally believed to interact with benzimidazoles may become accessible to the drugs. Furthermore, by docking albendazole-sulphoxide into a modelled H. contortus beta-tubulin molecule we offer a structural explanation for how the mutation conferring benzimidazole resistance in nematodes may act, as well as a possible explanation for the species-specificity of benzimidazole anthelmintics.

Polyoxyethylenated methyl esters of rape oil fatty acids as non-ionic surfactants in a model drug form with albendazole

Systematic research has been conducted on the applying of Rofams (oxyethylathed rape oil methyl esters) as solubilizing agents of albendazole. Homologous series of Rofams containing average amount of oxyethylene units (nTE) ranging between 20 to 60 was used for investigation. An attempt has been made to apply investigated surface active agents as an auxiliary in production of model tablets with albendazole. Basic morphological parameters of granulates (bulk density, tapped density, Carr index, angle of repose) were determined. The dissolution testing procedure, friability and standard deviation from an average tablet mass were conducted to evaluate properties of produced tablets. The solubility of albendazole increases in the presence of Rofams in the aqueous solutions. The highest amount of albendazole was solubilized in the aqueous solution of Rofam containing 20 oxyethylene units. The increase in the content of oxyethylene units in a molecule of surfactant leads to a subsequent decrease in the amount of solubilized albendazole. Studied compounds can be applied in suggested quantities in the formulation of solid dosage forms. Tablets obtained with their content obeyed standards of Polish Pharmacopoeia. Rofams are increasing the amount of albendazole liberated from the tablets what can result in increasing it's bioavailability.

Analytical and semipreparative resolution of enatiomers of albendazole sulfoxide by HPLC on amylose tris (3,5-dimethylphenylcarbamate) chiral stationary phases

Broad spectrum anthelmintic agent-albendazole sulfoxide (ABZSO) have been separated and semiprepared on amylose tris (3,5-dimethylphenylcarbamate) chiral stationary phases by HPLC using mobile phases contained with n-hexane and different alcohols. For analytical separation the influence of the nature and content of alcoholic modifiers on separation were systemically studied. Then, the analytical methods were scaled up to semipreparative loading to obtain small quantities (about 1 g) of both ABZSO enantiomers. Especially, different loading amounts were investigated for their effect on various parameters of semipreparative HPLC. In addition, optical rotation and circular dichroism (CD) of both ABZSO enantiomers collected were determined and single enantiomers were found stable in configuration for 1 year.

Comparative hepatic and extrahepatic enantioselective sulfoxidation of albendazole and fenbendazole in sheep and cattle

The enantioselective sulfoxidation of the prochiral anthelmintic compounds albendazole (ABZ) and fenbendazole (FBZ) was investigated in liver, lung and small intestinal microsomes obtained from healthy sheep and cattle. The microsomal fractions were incubated with a 40 microM concentration of either ABZ or FBZ. Inhibition of the flavin-containing monooxygenase (FMO) system was carried out by preincubation with 100 microM methimazole (MTZ) either with or without heat pretreatment (2 min at 50 degrees C). ABZ and FBZ were metabolized to the (+) and (-) enantiomers of their sulfoxide metabolites, named albendazole sulfoxide (ABZSO) and oxfendazole (OFZ), respectively. ABZ sulfoxidation rates were higher (p < 0.001) than those observed for FBZ. The FMO-mediated liver sulfoxidation of ABZ was enantioselective (100%) toward the (+) ABZSO production in both species. Liver sulfoxidation of FBZ by FMO was also enantioselective toward (+) OFZ (sheep = 65%; cattle = 79%). Cytochrome P450 was found to be mainly involved in the production of (-) ABZSO in the liver. MTZ did not affect the sulfoxidation of ABZ by lung microsomes, which may indicate that FMO is not involved in the production of ABZSO in this tissue. A significant (p < 0.05) inhibition of (-) ABZSO production by liver microsomes was observed after ABZ incubation in the presence of erythromycin (cattle = 21%) and ketoconazole (sheep = 36%). Both CYP3A substrates induced a reduction in the production of (-) ABZSO (sheep = 67-78%, cattle = 50-78%) by lung microsomes. Overall, the results reported here contribute to the identification of the metabolic pathways involved in the biotransformation of benzimidazole anthelmintics extensively used for parasite control in ruminants.

Enantioselective renal excretion of albendazole metabolites in patients with neurocysticercosis

The present study investigates the urinary excretion of the enantiomers of (+)- and (-)-albendazole sulfoxide (ASOX) and albendazole sulfone (ASON) in 12 patients with neurocysticercosis treated with albendazole for 8 days (7.5 mg/kg/12 h). Serial blood samples (0-12 h) and urine (three periods of 8 h) were collected after administration of the last dose of albendazole. Plasma and urine (+)-ASOX, (-)-ASOX, and ASON metabolites were determined by HPLC using a chiral phase column (Chiralpak AD) with fluorescence detection. The pharmacokinetic parameters (P < 0.05) for (+)-ASOX, (-)-ASOX, and ASON metabolites are reported as means (95% CI); amount excreted (Ae) = 3.19 (1.53-4.85) vs. 0.72 (0.41-1.04) vs. 0.08 (0.03-0.13) mg; plasma concentration-time area under the curve, AUC(0-24) = 3.56 (0.93-6.18) vs. 0.60 (0.12-1.08) vs. 0.38 (0.20-0.55) microg x h/ml, and renal clearance Cl(R) = 1.20 (0.66-1.73) vs. 2.72 (0.39-5.05) vs. 0.25 (0.13-0.37) l/h. Sulfone formation capacity, expressed as the Ae ratio ASON/ASOX + ASON, was 2.21 (1.43-2.99). These data point to enantioselectivity in the renal excretion of ASOX as a complementary mechanism to the metabolism responsible for the plasma accumulation of (+)-ASOX. The results also suggest that the metabolite ASON is partially eliminated as a reaction product of the subsequent metabolism.

In vitro activity of two phenyl-carbamate derivatives, singly and in combination with albendazole against albendazole-resistant Giardia intestinalis

Giardia intestinalis is one of the most prevalent parasites in adults and children in Mexico. Benzimidazoles have been proposed as a therapeutic alternative in the treatment of giardiasis. However, high-dose related toxicity and the development of resistance have emerged in clinical trials using this therapy. In the search of alternative drugs, we found that benzimidazole-resistant strains of fungi have shown increased sensitivity to phenyl-carbamates, hence, we developed several substituted phenyl-carbamates, two of which were tested against the protozoan parasite G. intestinalis in susceptible and albendazole-resistant Giardia strains. 4-R-ethyl-phenyl-carbamates IRE-6A and IRE-7B demonstrated antigiardial, albeit modest, activity when compared with albendazole, against susceptible and albendazole-induced resistant Giardia. However, when albendazole 0.38 microg/mL (MIC(50)) was combined with each IRE compound, a significant antigiardial synergism (fractional inhibitory concentration index (FICI < 0.5)) was obtained not only with sensitive cultures but also with resistant Giardia parasites. The results described here suggest a potential role for a combined therapy with phenyl-carbamates and sub-doses of benzimidazoles in the treatment of giardiasis.

Simultaneous determination of albendazole and its major active metabolite in human plasma using a sensitive and specific liquid chromatographic–tandem mass spectrometric method

A method for the simultaneous determination of albendazole (ABZ) and its major active metabolite albendazole sulfoxide (ABZ-SO) was developed and validated. The analytes were extracted from plasma samples by liquid-liquid extraction and analyzed using liquid chromatography-tandem mass spectrometry with an electrospray ionization interface. Estazolam was used as the internal standard. The assay was linear in the concentration range 0.4-200 ng/ml for ABZ and 4.0-2000 ng/ml for ABZ-SO. The intra- and inter-run precision (R.S.D.), calculated from quality control (QC) samples was less than 7.1 and 9.4% for ABZ and ABZ-SO, respectively. The accuracy as determined from QC samples was within +/- 3% for the analytes. Recoveries of ABZ and ABZ-SO were greater than 77 and 53%, respectively, over the calibration curve range. The method developed was successfully applied to pharmacokinetic studies of ABZ and ABZ-SO after an oral dose of 400 mg albendazole to healthy volunteers.

[Influence of mobile phase composition on chiral separation of albendazole sulfoxide racemates]

A chiral stationary phase (CSP) was prepared by coating amylose-tris(3,5-dimethylphenyl carbamate) (ADMPC) onto aminopropylated spherical silica gel. Albendazole sulfoxide (ABZSO) was directly resolved on the ADMPC-CSP by normal-phase high performance liquid chromatography (HPLC) using a series of binary and ternary mobile phases. The results indicated that the retention and stereoselectivity of ABZSO on ADMPC-CSP were significantly influenced by the kinds and the contents of the alcohols in mobile phases. The use of methanol and/or ethanol as alcoholic modifier achieved better separation of ABZSO. Effective and efficient chiral resolution was obtained by using ternary mobile phases: hexane/2-propanol/methanol or hexane/ethanol/methanol.

Ex Vivo Anthelmintic Activity of Albendazole-Sulphoxide Enantiomers

The antiparasitic activity of racemic albendazole-sulphoxide (Ricobendazole = racRBZ) and its (+) and (-) enantiomers was tested in an ex vivo murine model for Trichinella spiralis infection. Larvae were isolated from the muscle of infected mice and exposed to concentrations between 0.01 and 1 microg/ml of the racemic mixture or to each of its enantiomers. The activity of each compound was then assayed by measuring the ability of the treated larvae to infect naive mice (larval viability). At a concentration of 0.5 microg/ml, all 3 compounds were highly effective in reducing the viability of the larvae, achieving reductions of 91.26% (racRBZ), 96.7% (+), and 89.2% (-), when compared with untreated controls. At lower concentrations (0.1 microg/ml), only treatment with (+)RBZ rendered a significant reduction in larval viability in comparison with controls (84.3%; P < 0.01), whereas at 0.01 microg/ml, none of the compounds altered larval viability (P > 0.05).

The effect of solubilization on the oral bioavailability of three benzimidazole carbamate drugs

The effect of solubilization by complexation with povidone on the oral bioavailability of three anthelmintic benzimidazole carbamate drugs: mebendazole (MBZ), albendazole (ABZ) and ricobendazole (RBZ), was studied in mice. The following in vitro characteristics of the initial raw materials and the drug-povidone complexes were evaluated: melting point (MP); mean dissolution time (MDT); solubility constants (Cs) in n-octanol, acid (pH 1.2) and neutral (pH 7.4) aqueous media; apparent partition coefficients (P) and capacity factors (k'W) determined by HPLC. The following in vivo parameters were also evaluated: AUC(0-infinity), C(max), T(max) and MRT. The possible relationship between in vitro characteristics and in vivo parameters was explored and it was found that an increase in solubility, especially in acidic medium, leads to an increase in AUC and C(max) and a decrease in T(max). Therefore, dissolution seems to be the absorption limiting step for these drugs. For the in vivo parameters related to the amount of absorbed drug (AUC and C(max)), the best correlation was obtained with the in vitro characteristics related to solubility which are Cs, MP and MDT. On the other hand, there were good linear correlations between T(max) which is an in vivo parameter related to the rate of drug absorption, and the lipophilia/hydrophilia (logP and log k'W) relation-parameters.