Pharmacokinetics and tissue residues of albendazole sulphoxide and its metabolites in donkey after intramuscular injection

BACKGROUND

Various anti-parasitic drugs are used to control donkey parasitic diseases. The abuse of donkey drugs leads to the disposition of residues in the edible parts of treated donkeys.

OBJECTIVES

The aim of this study was to (1) analyse the pharmacokinetics of ABZSO to serve as reference for the dosage regimen in donkey; and (2) calculate the withdrawal times of the ABZSO in the tissue of the donkey.

METHODS

The concentrations of ABZSO and its metabolites in plasma and tissues were determined using high-performance liquid chromatography with an ultraviolet detector. Pharmacokinetic analysis was performed by the programme 3p97.

RESULTS

The plasma concentrations of ABZSO and ABZSO2 concentration-time data in donkey conformed to the absorption one-compartment open model. Thet 1 / 2 k e ${{{t1}} \!\mathord{/ {\vphantom { {2{{k}_{\mathrm{e}}}}}}}}$ of ABZSO was 0.67 h, whereas the t1/2 k e was 12.93 h; the Cmax and the Tp were calculated as 0.58 μg mL-1 and 3.01 h. The Vd/F of ABZSO was estimated to be 10.92 L kg-1; the area under the curve (AUC) was 12.81 μg mL-1 h. The Cmax and AUC values of ABZSO were higher than those of ABZSO2; however, t1/2 K e and Vd/F were lower. Other pharmacokinetics parameters were similar between the two metabolites.

CONCLUSIONS

The results revealed that ABZSO2 was the main metabolite of ABZSO in donkey plasma. The concentrations of ABZSO and its chief metabolite (ABZSO2) were detected in liver, kidney, skin and muscle; however, ABZ-SO2NH2 was only detected in liver and kidney. The results also revealed that the depletion of ABZSO and its metabolite in donkey was longer, especially in skin.

Comparative proteomics analysis of Trichinella spiralis muscle larvae exposed to albendazole sulfoxide stress

The drug albendazole (ABZ) has a positive effect against Trichinella spiralis infection and has been used for the treatment and prevention of trichinellosis in humans and animals. However, the molecular mechanism ofthe effects of ABZ on T. spiralis remains unknown. Albendazole sulfoxide (ABZSO) is the main intermediary metabolic product of ABZ, and it is often used as a substitute for ABZ in metabolism and bioavailability research. Herein, isobaric tagging reagents for relative and absolute quantification (iTRAQ)-based LC-MS/MS analysis was used to identify the effect of ABZSO on the proteome of T. spiralis muscle larvae in vitro. 3795 proteins were quantified from 22974 unique peptides. Comparative proteomics analysis displayed that 417 proteins were remarkably differentially expressed in ABZSO-treated larvae, of which 213 proteins were up-regulated and 204 proteins were down-regulated. Quantitative real-time PCR of ten randomly-selected genes verified the proteomic data. Gene ontology annotation and KEGG pathway analysis showed that most of the differentially expressed proteins were involved in cell apoptosis, signal pathway, amino acid metabolism, protein synthesis/assembly/degradation and other biological processes. This study firstly provided the comprehensive proteomics data of T. spiralis in response to ABZSO, and would help us to deeply understand the molecular mechanism of ABZSO effects on T. spiralis.

Exposure of Heligmosomoides polygyrus and Trichuris muris to albendazole, albendazole sulfoxide, mebendazole and oxantel pamoate in vitro and in vivo to elucidate the pathway of drug entry into these gastrointestinal nematodes

Millions of people are treated with anthelmintics to control soil-transmitted helminth infections; yet, drug distribution in the plasma and gastrointestinal tract compartments and the pathway of drug uptake into gastrointestinal nematodes responsible for the pharmacological effect are unknown. We assessed the distribution and uptake of albendazole, albendazole sulfoxide, albendazole sulfone in the hookworm Heligmosomoides polygyrus in vitro and in vivo as well as the distribution and uptake of albendazole, mebendazole, and oxantel pamoate in the whipworm Trichuris muris in vitro and in vivo. Oral and intraperitoneal treatments (100 mg/kg) were studied. Drug quantities in helminths and host compartments (stomach, the contents and mucosa of the small and large intestine, and the plasma) were determined using HPLC-UV/vis and anthelmintic activities were recorded using phenotypic readout. The influence of 1-aminobenzotriazole (ABT), an irreversible and unspecific cytochrome P450 inhibitor, on albendazole disposition in mice harboring H. polygyrus was evaluated. In vivo, albendazole was found in quantities up to 10 nmol per ten H. polygyrus and up to 31 nmol per ten T. muris. ABT did not change the levels of albendazole or its metabolites in the plasma of mice harboring H. polygyrus or in H. polygyrus, whereas drug levels in the gastrointestinal tract of host mice doubled. Mebendazole and oxantel pamoate quantities per ten T. muris were as high as 21 nmol and 34 nmol, respectively. Albendazole revealed a very dynamic distribution and high rate of metabolism, hence, H. polygyrus and T. muris are exposed to albendazole and both metabolites via multiple pathways. Diffusion through the cuticle seems to be the crucial pathway of oxantel pamoate uptake into T. muris, and likely also for mebendazole. No relationship between concentrations measured in helminths and concentrations in plasma, intestinal content and mucosa of mice, or drug efficacy was noted for any of the drugs studied.

Intra-cystic concentrations of albendazole-sulphoxide in human cystic echinococcosis: a systematic review and analysis of individual patient data

Cystic echinococcosis (CE) is a widespread zoonosis caused by the species complex Echinococcus granulosus. Albendazole (ABZ)-the first-line anthelminthic drug for medical treatment of CE-is metabolized in vivo to the active derivative ABZ-sulphoxide (ABZ-SO). Target-site ABZ-SO concentrations in the hydatid cyst mediate the anthelminthic effect in CE. Primary outcome of this systematic review of individual patient data was the intra-cystic ABZ-SO concentration stratified by cyst size, location, calcification status and use of praziquantel. Studies reporting intra-cystic ABZ-SO concentrations in humans were identified by a systematic search. A pooled analysis of individual patient data was performed to assess intra-cystic concentrations. Pharmacokinetic data of 121 individual cysts were analysed. There was no correlation between plasma and intra-cystic ABZ-SO concentrations (rho = -0.03, p = 0.76). Intra-cystic drug concentrations were also not associated with sex and treatment duration. Use of praziquantel in combination with ABZ was associated with higher plasma (median 540 vs. 240 μg/L; p = 0.04) but not intra-cystic ABZ-SO concentrations (median 220 vs. 199 μg/L; p = 0.36). Relative drug concentrations in hepatic cysts were higher than in other cysts (0.8 vs. 0.4; p = 0.05). Intra-cystic concentrations were higher in calcified than non-calcified cysts (median 897 vs. 245 μg/L; p = 0.03). There was a trend towards higher intra-cystic concentrations in smaller sized cysts (β = -17.2 μg/L/cm; 95th CI, -35.9 to 1.6; p = 0.07). This study demonstrates that mean intra-cystic drug concentrations are similar to plasma concentrations on a population level. However, in individual patients plasma concentrations are not directly predictive for intra-cystic concentrations. The use of booster drugs was not associated with higher intra-cystic ABZ-SO concentrations in this analysis.

[Efficacy of albendazole chitosan microspheres against Echinococcus granulosus infection in mice]

OBJECTIVE

To observe the therapeutic effect of albendazole chitosan microspheres (ABZ-CS-MPs) on cystic echinococcosis in mice.

METHODS

Two hundred male kunming mice were each infected by intraperitoneal inoculation of about 5 000 viable protoscoleces of Echinococcus granulosus. Another 20 mice were kept as blank control. After 12 weeks post infection, the mice were randomly divided into four groups named as infection control group (n = 20), ABZ-CS-MPs group, albendazole liposome (L-ABZ) group, and albendazole tablet group. The latter three treatment groups were then each divided into three subgroups (n = 20) by given the dose of 37.5, 75.0, and 150.0 mg/kg for three times per week, respectively. After 12 weeks of treatment, all mice were sacrificed. The weight of hydatid cysts was measured and the inhibition rate were calculated. Mouse liver was observed. The histopathological changes of E. granulosus were observed by microscopy. The concentration of albendazole sulfoxide in plasma and liver tissues was determined by high-performance liquid chromatography.

RESULTS

Compared with the other treatment groups, the turbidity of contained fluid, the consolidation level and calcification level of hydatid cysts in ABZ-CS-MPs group were higher. The average weight of hydatid cysts in each treatment group was lower than that of infection control group [(3.19 +/- 2.94) g] (P < 0.05). The cyst weight in 37.5, 75.0, and 150.0 mg/kg ABZ-CS-MPs group [(0.28 +/- 0.28), (0.24 +/- 0.22), and (0.20 +/- 0.19) g, respectively] was lower than that of albendazole tablet groups [(0.77 +/- 0.74), (0.55 +/- 0.42), (0.76 +/- 0.35) g] (P < 0.05). Among the same dosage groups, the inhibition rate in ABZ-CS-MPs group (from low to high dosage sub-group: 91.1%, 92.6%, and 93.7%, respectively) was highest. In 75.0 mg/kg ABZ-CS-MPs group, there were 15 mice with class I (degeneration) and II (necrosis) pathological changes of E. granulosus hydatid. The number of mice with class I and II pathological changes in each dosage ABZ-CS-MPs sub-group and L-ABZ sub-group was more than that of albendazole tablet group (P<0.05). Plasma concentration of albendazole sulfoxide in 75.0 and 150.0 mg/kg ABZ-CS-MPs sub-groups [(0.83 +/- 0.39), (0.80 +/- 0.5) microg/ml] were higher than that of L-ABZ sub-groups [(0.34 +/- 0.03), (0.43 +/- 0.15) microg/ml] and albendazole tablet sub-groups [(0.31 +/- 0.02), (0.40 +/- 0.10) microg/ml] (P < 0.05). Compared with 37.5, 75.0, and 150.0 mg/kg albendazole tablet sub-groups [(0.04 +/- 0.02), (0.07 +/- 0.04), (0.04 +/- 0.0) microg/g], the albendazole sulfoxide concentration in liver tissue was higher in ABZ-CS-MPs sub-groups [(0.33 +/- 0.06), (0.45 +/- 0.31), (0.50 +/- 0.30) microg/g] (P < 0.05). In 37.5 mg/kg dosage sub-group, the albendazole sulfoxide concentration in liver tissue in ABZ-CS-MPs group was higher than that of L-ABZ group [(0.14 +/- 0.19) microg/g] (P < 0.05).

CONCLUSION

ABZ-CS-MPs can reduce the weight of hydatid cyst and increase the concentration of al-bendazole sulfoxide in plasma and liver tissue of mice.

Pharmacokinetic investigation of albendazole and praziquantel in Thai children infected withGiardia intestinalis

The pharmacokinetics of albendazole/albendazole sulphoxide and praziquantel were investigated in Thai children with Giardia infection. Twenty school-age children were randomly allocated to receive either a single oral dose of albendazole (400 mg/child) or the same dose of albendazole given concurrently with a single oral dose of praziquantel (20 mg/kg). The concentrations of albendazole/albendazole sulphoxide and praziquantel in plasma samples, collected at intervals in the first 24 h post-treatment, were then quantified using HPLC with ultra-violet detection. No significant pharmacokinetic interaction between the albendazole and praziquantel was demonstrated. For albendazole sulphoxide, the active metabolite of albendazole, there was marked inter-individual variation in the maximum plasma concentration and the 'area under the curve'. The pharmacokinetics of albendazole sulphoxide were similar whether albendazole was given alone or in combination with praziquantel.

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.

A cell-based screen reveals that the albendazole metabolite, albendazole sulfone, targets Wolbachia

Wolbachia endosymbionts carried by filarial nematodes give rise to the neglected diseases African river blindness and lymphatic filariasis afflicting millions worldwide. Here we identify new Wolbachia-disrupting compounds by conducting high-throughput cell-based chemical screens using a Wolbachia-infected, fluorescently labeled Drosophila cell line. This screen yielded several Wolbachia-disrupting compounds including three that resembled Albendazole, a widely used anthelmintic drug that targets nematode microtubules. Follow-up studies demonstrate that a common Albendazole metabolite, Albendazole sulfone, reduces intracellular Wolbachia titer both in Drosophila melanogaster and Brugia malayi, the nematode responsible for lymphatic filariasis. Significantly, Albendazole sulfone does not disrupt Drosophila microtubule organization, suggesting that this compound reduces titer through direct targeting of Wolbachia. Accordingly, both DNA staining and FtsZ immunofluorescence demonstrates that Albendazole sulfone treatment induces Wolbachia elongation, a phenotype indicative of binary fission defects. This suggests that the efficacy of Albendazole in treating filarial nematode-based diseases is attributable to dual targeting of nematode microtubules and their Wolbachia endosymbionts.

Pharmacokinetics and tissue residues of hydrochloric acid albendazole sulfoxide and its metabolites in crucian carp (Carassius auratus) after oral administration

The pharmacokinetics and residues elimination of hydrochloric acid albendazole sulfoxide (ABZSO) and its metabolites were studied in healthy crucian carp (Carassius auratus, 250 ± 30 g) kept at water temperatures of 10 °C and 25 °C. The concentrations of ABZSO and its metabolites concentration in plasma and tissues were determined using high-performance liquid chromatography (HPLC) using an ultraviolet detector. The results revealed that the plasma concentration of ABZSO in plasma was significantly higher than that of albendazole sulfone (ABZSO(2)), whereas albendazole-2-aminosulfone (ABZ-SO(2)NH(2)) was not detected. The plasma concentrations of ABZSO and its main metabolite ABZSO(2) concentration-time data were fitted using a single-compartment model at 10 °C and 25 °C. The absorption half-life (t₁/₂ka) of ABZSO was 3.86 h at 10 °C and 1.29 h at 25 °C, whereas the elimination half-life (t₁/₂ke) was 16.34 h at 10 °C and 6.72 h at 25 °C; the maximum plasma concentration (C(max)) and the time-point of maximum plasma concentration (T(p)) were calculated as 3.20 μg mL(-1) and 10.58 h at 10 °C, 4.39 μg mL(-1) and 3.80 h at 25 °C. The distribution volume (V(d)/F) of ABZSO was estimated to be 1.99 L kg(-1) at 10 °C and 1.53 L kg(-1) at 25 °C; the total body clearance (CL(b)) of ABZSO were computed as 0.08 and 0.19 L/(h kg) at 10 and 25 °C, respectively; the areas under the concentration-time curve (AUC) was 118.22 μg mL(-1)h at 10 °C and 63.12 μg mL(-1)h at 25 °C. The [Formula: see text] of ABZSO(2) was found to be 6.39 °C at 10 °C and 3.73 h at 25 °C, whereas the [Formula: see text] was 12.86 h at 10 °C and 6.56 h at 25 °C; the C(max) and T(p) of ABZSO(2) was calculated as 0.78 μg mL(-1) and 12.82 h at 10 °C, 1.03 μg mL(-1) and 7.04 h at 25 °C, respectively; the V(d)/F of ABZSO(2) were estimated to be 6.43 L kg(-1) at 10 °C and 4.61 Lkg(-1) at 25 °C; the CL(b) of ABZSO(2) were computed as 0.34 and 0.49 L/(h kg) at 10 °C and 25 °C, respectively; the AUC of ABZSO(2) were 28.86 μg mL(-1)h at 10 °C and 20.52 μg mL(-1)h at 25 °C. It was demonstrated that ABZSO(2) was the main metabolite of ABZSO. The concentrations of ABZSO and its main metabolite (ABZSO(2)) were detected in muscle, skin, liver and kidney, whereas ABZ-SO(2)NH(2) was only detected in liver and kidney. The ABZSO and it metabolite (ABZSO(2)) could still be detected at 4 d time-point after administration at both temperatures in all tissues. The results revealed that the depletion of ABZSO and its metabolite (ABZSO(2)) in crucian carp was slower with a long half-life time, especially at lower water temperature.

Evaluation of potential embryo toxicity of albendazole sulphoxide in CF1 mice

Benzimidazole compounds are used in both humans and animals for controlling helminth parasites. Albendazole has teratogenic effects attributed to its active metabolite albendazole sulphoxide. The aim of this work was to evaluate the effect of the latter compound when administered to pregnant CF1 mice during the preimplantation period. Females were superovulated by intraperitoneal injection of 10 IU of eCG and 10 IU of hCG (48h later) and were paired with males of proven fertility. Albendazole sulphoxide (200 mg/kg) was orally administered by gavages at day 1, 2 or 3 of pregnancy; the control group received only the vehicle (carboxymethylcellulose). Females were killed by cervical dislocation at day 4 of pregnancy and embryos were flushed from uteri with Ham F10 media supplemented with bovine serum albumin (0.4%). Number of collected embryos per female, percentage of morphologically normal embryos, differentiation rate and number of cells per embryos were recorded. The variables were analyzed on a per litter basis by Kruskal-Wallis test. There was no effect of albendazole sulphoxide on parameters evaluated (P>0.05). We conclude that the preimplantation mouse embryo development was not significantly affected by albendazole sulphoxide.

Microbial transformation of albendazole

Screening scale studies were performed to biotransform anthelmintic drug albendazole by using twelve bacterial strains representing six genera and five actinomycetes cultures. Among the cultures studied, Bacillus subtilis MTCC 619, Escherichia coli MTCC 118 and Klebsiella pneumoniae MTCC 109 could transform albendazole to one metabolite whereas, Enterobacter aerogenes NCIM 2695, Klebsiella aerogenes NCIM 2258, Pseudomonas aeruginosa NCIM 2074 and Streptomyces griseus NCIM 2622 could transform albendazole into two metabolites in significant quantities. The transformation of albendazole was identified by HPLC. Based on LC-MS-MS data, the two metabolites were predicted to be albendazole sulfoxide (M1) and albendazole sulfone (M2), the major mammalian metabolites reported previously. Since M1 is active metabolite, the results prove the versatility of microorganisms to perform industrially attractive chemical reactions.

Population pharmacokinetics of albendazole in patients with neurocysticercosis

OBJECTIVES

To determine a population pharmacokinetic model of the antihelmintic drug, albendazole, and identify the factors influencing the pharmacokinetic parameters in patients with neurocysticercosis.

METHODS

A prospective study was performed in 90 patients receiving 30 mg/kg/day of albendazole for 8 days. Blood samples were collected at steady state. Plasma concentrations of albendazole sulfoxide, the main active metabolite of albendazole, were determined by HPLC. The population pharmacokinetics analysis was performed using non-linear mixed-effect modeling (NONMEM). A one-compartment model with first order absorption and elimination was used.

RESULTS

Body weight was included empirically on CL/F and V/F using an allometric relationship. Although none of the investigated covariates had a significant influence on the pharmacokinetic parameters of albendazole, the final model identified two subpopulations on the bioavailability parameter. One subpopulation comprising of 27% of the total population had a bioavailability of 28%, with the remaining subpopulation defined to have complete bioavailability. The CL/F and V/F for a standard 70 kg individual was determined to be 51.6 l/h and 4560 l, respectively. Interindividual variability in CL/F was 32%; the residual unexplained variability was 32%.

CONCLUSIONS

The considerable variability reported in albendazole pharmacokinetics and plasma concentrations is likely due to issues related to bioavailability. With one-fourth of the population absorbing as little as 30% of the drug relative to others, low drug exposures might be responsible for treatment failures. Therapeutic drug monitoring may be warranted to optimize the eradication of the infecting parasite.

[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.

Determination of albendazole and its metabolites in the muscle tissue of hybrid striped and largemouth bass using liquid chromatography with fluorescence detection

A liquid chromatographic method was developed for the determination of albendazole and its metabolites albendazole sulfoxide, albendazole sulfone, and albendazole-2-aminosulfone from largemouth and hybrid striped bass muscle tissue with adhering skin. The muscle tissue samples were made alkaline with potassium carbonate and extracted with ethyl acetate. The extracts were further subjected to cleanup by using a series of liquid-liquid extractions. After solvent evaporation, the residue was reconstituted in mobile phase and chromatographed. The chromatography was carried out on a reversed-phase Luna C18 column, using acetonitrile-methanol buffer as the mobile phase. The analytes were detected by fluorescence with excitation and emission wavelengths of 290 and 330 nm, respectively. The average recoveries from the fortified muscle tissue of the 2 fish species for albendazole (25-100 ppb), albendazole sulfoxide (8.75-52.5 ppb), albendazole sulfone (1-10 ppb), and albendazole-2-aminosulfone (10-100 ppb) were 89, 82, 99, and 74%, respectively. The coefficient of variation for each compound was <20% in all cases. The procedure was applied to the determination of albendazole and its 3 metabolites in the muscle tissue of the 2 fish species after orally dosing them with albendazole.

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).

Simultaneous determination of albendazole metabolites, praziquantel and its metabolite in plasma by high-performance liquid chromatography–electrospray mass spectrometry

The analysis of albendazole sulfoxide, albendazole sulfone, praziquantel and trans-4-hydroxypraziquantel in plasma was carried out by high-performance liquid chromatography-mass spectrometry ((LC-MS-MS). The plasma samples were prepared by liquid-liquid extraction using dichloromethane as extracting solvent. The partial HPLC resolution of drug and metabolites was obtained using a cyanopropyl column and a mobile phase consisting of methanol:water (3:7, v/v) plus 0.5% of acetic acid, at a flow rate of 1.0 mL/min. Multi reaction monitoring detection was performed by electrospray ionization in the positive ion mode, conferring additional selectivity to the method. Method validation showed relative standard deviation (precision) and relative errors (accuracy) lower than 15% for all analytes evaluated. The quantification limit was 5 ng/mL and the linear range was 5-2500 ng/mL for all analytes. The method was used for the determination of drug and metabolites in swine plasma samples and proved to be suitable for pharmacokinetic studies.

Absorption and metabolism of albendazole after intestinal ischemia/reperfusion

Pathophysiological processes involving inflammatory response may affect absorption and biotransformation of some drugs, modifying their pharmacokinetic behaviour. Ischemia/reperfusion (I/R) injury has been used as a model for inflammatory processes. The aim of this work was to study the effect of intestinal I/R injury on the absorption and metabolism processes of one orally administered drug, albendazole that is anthelmintic drug, it undergoes intestinal bioconversion into albendazole sulfoxide by two enzymatic systems, cytochromes P450 (CYP450) and flavin-containing monooxygenase (FMO). Male Wistar rats were used to study the influence of I/R in the intestinal absorption and metabolism of albendazole, after 60 min of mesenteric occlusion and 30 min of reperfusion. The intestinal studies were performed in microsomal, and everted ring incubations. During in situ studies, the I/R group had faster disappearance of albendazole from the lumen. In addition, albendazole only appeared in blood samples of the I/R group, while albendazole sulfoxide appeared in both samples and was higher in the control group. These findings are supported by significant reductions of albendazole sulfoxide formation in intestinal everted ring assays and in microsomal incubations after the I/R process. Both metabolizing systems, CYP4503A and FMO, were affected by I/R. Our data indicate that I/R injury, considered as an inflammatory model, reduces absorption and metabolism processes of albendazole.

A dual anthelmintic treatment strategic scheme for the control of fasciolosis in dairy sheep farms

A clinical longitudinal field trial was conducted on a dairy sheep farm in southern Italy to assess the effectiveness of a novel anthelmintic treatment strategic scheme against Fasciola hepatica. The scheme utilizes a dual anthelmintic treatment (DAT), i.e., the use of either one of two different anthelmintics on the flock, albendazole sulphoxide (SO) at 1-month intervals and rafoxanide at 2-month intervals, administered to the lactating and non-lactating animals, respectively. The DAT strategic scheme lasted 3 years. In Year 1 and Year 2, shotgun monthly DATs for 5 consecutive months (July, August, September, October, and November) were performed on the flock. In Year 3 there was only one monthly DAT, in July. Overall, the DAT scheme reduced the prevalence of F. hepatica infection by 94.4% (from an average prevalence of 71.1% during the pre-DAT period to an average prevalence of 4.0% during Year 3), and the eggs/gram of faeces (EPG) from 29.3 to 1.3. In conclusion, the DAT strategic scheme reported in the present study successfully reduced both the prevalence and EPGs of F. hepatica to a level at which there were no longer any clinical symptoms of the disease. This scheme did not influence the albendazole SO efficacy against GI nematodes and might be used for the treatment of fasciolosis in dairy sheep farms.

Plasma disposition and faecal excretion of netobimin metabolites and enantiospecific disposition of albendazole sulphoxide produced in ewes

Netobimin (NTB) was administered orally to ewes at 20 mg/kg bodyweight. Blood and faecal samples were collected from 1 to 120 h post-treatment and analysed by high-performance liquid chromatography (HPLC). Using a chiral phase-based HPLC, plasma disposition of albendazole sulphoxide (ABZSO) enantiomers produced was also determined. Neither NTB nor albendazole (ABZ) was present and only ABZSO and albendazole sulphone (ABZSO(2)) metabolites were detected in the plasma samples. Maximum plasma concentrations (C(max)) of ABZSO (4.1 +/- 0.7 microg/ml) and ABZSO(2) (1.1 +/- 0.4 microg/ml) were detected at (t(max)) 14.7 and 23.8 h, respectively following oral administration of netobimin. The area under the curve (AUC) of ABZSO (103.8 +/- 22.8 (microg h)/ml) was significantly higher than that ABZSO(2)(26.3 +/- 10.1 (microg h)/ml) (p < 0.01). (-)-ABZSO and (+)-ABZSO enantiomers were never in racemate proportions in plasma. The AUC of (+)-ABZSO (87.8 +/- 20.3 (microg h)/ml) was almost 6 times larger than that of (-)-ABZSO (15.5 +/- 5.1 (microg h)/ml) (p < 0.001). Netobimin was not detected, and ABZ was predominant and its AUC was significantly higher than that of ABZSO and ABZSO(2), following NTB administration in faecal samples (p > 0.01). Unlike in the plasma samples, the proportions of the enantiomers of ABZSO were close to racemic and the ratio of the faecal AUC of (-)-ABZSO (172.22 +/- 57.6 (microg h)/g) and (+)-ABZSO (187.19 +/- 63.4 (microg h)/g) was 0.92. It is concluded that NTB is completely converted to ABZ by the gastrointestinal flora and absorbed ABZ is completely metabolized to its sulphoxide and sulphone metabolites by first-pass effects. The specific behaviour of the two enantiomers probably reflects different enantioselectivity of the enzymatic systems of the liver that are responsible for sulphoxidation and sulphonation of ABZ.

Pharmacokinetics of albendazole in New Zealand white rabbits: oral versus intraperitoneal administration

BACKGROUND

Recent studies from our group have shown the potent antitumor effects of albendazole (ABZ). It was hypothesized that intraperitoneal (i.p.) administration of ABZ in peritoneal carcinomatosis (PC) could lead to long exposure of tumor cells to high concentration of the drug and possibly to reduced systemic toxicity.

MATERIALS AND METHODS

Eight male New Zealand white rabbits were randomized into two groups, all given a single dose of ABZ 150 mg/kg suspended in 0.5% carboxymethylcellulose (CMC), either as i.p. injection, or as oral administration. The concentration of ABZ and its metabolites in plasma were determined using a high performance liquid chromatography method.

RESULTS

The parent drug was detected in plasma after oral and i.p. administration. The C(max) of albendazole sulphoxide (ABZ-SO) resulted in a much higher plasma concentration in the oral group (41.86 microg/ml) than in the i.p. group (16.84 microg/ml, p < 0.05). The area under the concentration over time curve of ABZ-SO in the oral group (1010.43 microg/ml/h) was also significantly higher than that of the i.p. group (528.33 microg/ml/h, p < 0.05). Compared to oral administration, the i.p. administration of an ABZ suspension led to significantly lower plasma levels of the major metabolite (ABZ-SO). This could have considerable therapeutic benefits in the regional treatment of PC.

Efficacy of nitazoxanide, tizoxanide and tizoxanide/albendazole sulphoxide combination against Taenia crassiceps cysts

OBJECTIVES

Neurocysticercosis is a common parasitic disease in the CNS in humans caused by the metacestode Taenia solium, with high incidence in developing countries. Albendazole is the drug of choice. However, a wide interindividual variability in the response has been reported. In order to evaluate alternative treatment options, the in vitro efficacy of nitazoxanide, its main metabolite tizoxanide as well as the tizoxanide and albendazole sulphoxide combination was tested against Taenia crassiceps cysts.

METHODS

T. crassiceps cysts were incubated in culture medium containing different concentrations of nitazoxanide, tizoxanide and albendazole sulphoxide (0.037-0.42 microg/mL). The effect of the tizoxanide and albendazole sulphoxide combination was evaluated in a fixed-concentration ratio (1:1). Isobolographic analyses were used to define the kind of interaction between drugs. Morphological and ultrastructural alterations over the parasite tissue were observed by light and transmission electron microscopy.

RESULTS

Nitazoxanide and tizoxanide exhibited cestocidal activity which was time-concentration-dependent. The EC(50) values were 0.15, 0.12 and 0.080 microg/mL for nitazoxanide, tizoxanide and albendazole sulphoxide, respectively. No statistical differences between EC(50) values were found, indicating that nitazoxanide and tizoxanide are equally potent as albendazole sulphoxide. The effect of the tizoxanide and albendazole sulphoxide combination was faster than that observed with each drug alone. Isobolographic analysis showed that the effect of the combination was additive. Nitazoxanide and tizoxanide had an effect on the germinal layer, where lipid droplets were found. Nitazoxanide and tizoxanide produced less damage than albendazole sulphoxide on the germinal layer. After the tizoxanide and albendazole sulphoxide combination, a high accumulation of lipid droplets within the germinal layer of the parasite was found.

CONCLUSIONS

Our results suggest that nitazoxanide in combination with albendazole could be useful for treatment of cysticercosis infections. Additional in vivo studies are required to confirm this hypothesis.

Pharmacokinetics of ricobendazole after its intravenous, intraruminal and subcutaneous administration in sheep

Ricobendazole (RBZ) was administered in sheep at the dose rate of 5 mg/kg by intravenous (i.v.) route as a 10% experimental solution, by the intraruminal (i.r.) route as a 10% experimental suspension, and by the subcutaneous (s.c.) route as a 10% commercial formulation available in Argentina. Blood samples were drawn during a 60 h period. Plasma concentrations of RBZ and its inactive metabolite albendazole sulphone (ABZSO2) were determined by high-performance liquid chromatography. The pharmacokinetic parameters were determined by compartmental analysis. The fitting of the data was done by weighted least-squares non-linear regression analysis. The pharmacokinetic parameters were estimated for every animal by simultaneous fitting of the plasma concentrations profiles of RBZ obtained after its administration by the three routes. The kinetic analysis of ABZSO2 was performed by a statistical moment approach. Ricobendazole bioavailability was poor after i.r. administration, whereas high and sustained plasma concentrations and higher bioavailability were obtained after s.c. administration. A simple two-compartment open model explains in a mechanical sense the pharmacokinetic behaviour of RBZ in sheep and allows us to estimate the real first-order constant rate of absorption and the loss of drug from the absorption site after its administration by s.c. and i.r. routes.

Interaction of enrofloxacin with breast cancer resistance protein (BCRP/ABCG2): influence of flavonoids and role in milk secretion in sheep

The ATP-binding cassette (ABC) transporter breast cancer resistance protein (BCRP)/ABCG2 is a high-capacity efflux transporter with wide substrate specificity located in apical membranes of epithelia, which is involved in drug availability. BCRP is responsible for the active secretion of clinically and toxicologically important substrates to milk. The present study shows BCRP expression in sheep and cow by immunoblotting with MAb (BXP-53). Vanadate-sensitive ATPase activity with specific BCRP substrates and inhibitors was measured in bovine mammary gland homogenates. To assess the role of BCRP in ruminant mammary gland we tested the fluoroquinolone enrofloxacin (ENRO). In polarized cell lines, ENRO was transported by Bcrp1/BCRP with secretory/absorptive ratios of 6.5 and 2 respectively. The efflux was blocked by the BCRP inhibitor Ko143. ENRO pharmacokinetics in plasma and milk was studied in sheep after co-administration of drug (2.5 mg/kg, i.v.) and genistein (0.8 mg/kg, i.m.) or albendazole sulfoxide (2 mg/kg, i.v) as BCRP inhibitors. Concomitant administration of BCRP inhibitors with ENRO had no significant effect on the plasma disposition kinetics of ENRO but decreased ENRO concentrations in milk.

Assessments of pharmacokinetic drug interactions and tolerability of albendazole, praziquantel and ivermectin combinations

The pharmacokinetic interactions and tolerability of albendazole, praziquantel and ivermectin combinations were assessed in 23 healthy Thai volunteers (12 males and 11 females). The study was an open, randomised, three-way crossover design in which each subject attended the study on three separate occasions (Phases I, II and III), of 4 d or 8 d each, with at least 1 or 2 weeks (but not longer than 2 months) between each phase. All subjects received the three study drug regimens as follows: regimen I, oral praziquantel (40 mg/kg body weight); regimen II, oral ivermectin (200 microg/kg body weight) given concurrently with an oral dose of albendazole (400 mg); and regimen III, oral ivermectin given concurrently with albendazole and praziquantel. All treatment regimens showed acceptable tolerability profiles. The incidence of overall drug-related adverse events was significantly higher following regimens I (12/23) and III (7/23) compared with that following regimen II (0/23). Six statistically significant changes in the pharmacokinetic parameters of albendazole sulphoxide (Cmax, AUC0-infinity, Vz/F, CL/F), praziquantel (Vz/F) and ivermectin (AUC0-infinity) were observed when the three drugs were given concurrently. However, based on US Food and Drug Administration criteria, these changes were not considered of clinical relevance.

Evaluation of the efficacy of albendazole sulphoxide and praziquantel in combination on Taenia crassiceps cysts: in vitro studies

OBJECTIVES

Praziquantel and albendazole are currently used for chemotherapeutic treatment of neurocysticercosis. Albendazole has been found to be more effective than praziquantel; however, it is well known that not all patients will show a complete resolution of cysts. Searching for more effective treatments, this study was designed to evaluate the effect of the combination of praziquantel and albendazole sulphoxide in a Taenia crassiceps in vitro model as well as the kind of interaction between both drugs.

METHODS

In order to determine the concentration that produced 50% effect (EC50), T. crassiceps cysts were incubated in culture medium containing praziquantel (0.005-0.04 microg/mL), albendazole sulphoxide (0.021-0.16 microg/mL) or the combination of praziquantel and albendazole sulphoxide in a fixed-dose ratio (1:1). The experimental concentration (EC50Exp) of the combination was determined from the concentration-response curve constructed from the combined drug treatment. Isobolographic analyses were used to define the nature of the interaction between praziquantel and albendazole sulphoxide. Morphological and ultrastuctural alterations after different treatments over the parasite tissue were observed by light and transmission electron microscopy.

RESULTS

The changes in ultrastructure were more marked with the praziquantel and albendazole sulphoxide combination. Also the cysticidal effect of the combination was observed earlier than that of each drug alone. When isobolographic analysis was employed, we found that the experimental EC50 value (0.042 microg/mL) was not significantly different from the theoretical EC50 value (0.035 microg/mL), which indicates an additive interaction between praziquantel and albendazole sulphoxide.

CONCLUSIONS

Our study suggests that the combination of praziquantel and albendazole sulphoxide could potentially improve the current neurocysticercosis treatment.

Preoperative albendazole and scolices viability in patients with hepatic echinococcosis

To determine the plasmatic and intracystal concentrations of albendazole sulfoxide (AS) and correlate them with the viability of the scolices in patients surgically treated for hepatic hydatid cysts (HHC) that received albendazole preoperatively, as an indirect way of evaluating the scolicide efficacy of the drug. A non-consecutive series of patients with uncomplicated HHC, underwent operation at the Department of Surgery, Regional Hospital of Temuco, Chile, between 2001 and 2002. The patients were given 10 mg/kg/day of albendazole for 4 days prior to the surgery. Intraoperative samples of venous blood and hydatid fluid were taken, in which the plasmatic concentration (PIC) and intracystal concentration (ICC) of AS were measured by means of high-performance liquid chromatography. With the remaining hydatid fluid, the viability of the scolices was examined. The following variables were taken into consideration: diameter, type of cyst, number of cysts, and development of cyst-biliary communications. Descriptive statistics were used in the calculation of medians, averages, and standard deviations, and analytical statistics were used for the comparison of continuous variables applying the t-test and the Mann-Whitney U-test. A total of 26 patients with HHC, with a median age of 39.5 years (range: 16-80 years); 16 were women (61.5%). Nineteen patients presented only one cyst (73.1%), and the diametric median of the cysts was 14.5 cm (range: 7-30). Fourteen patients presented univesicular cysts (53.9%), and the remaining 12 had multivesicular cysts (46.1%). The average PIC of AS in the whole series was 1.88 +/- 0.5 microg/ml and the ICC was 0.26 +/- 0.2 microg/ml. The ICC in viable hydatid cysts was 0.25 microg/ml versus 0.28 microg/ml in non-viable cysts (p = 0.7556). The absence of association between intracystal levels of AS and the viability of the scolices allows one to posit indirectly that albendazole is ineffective as a scolicidal agent administered preoperatively for 4 days.

Development and optimization of a rapid HPLC method for analysis of ricobendazole and albendazole sulfone in sheep plasma

A simple, rapid and reliable high performance liquid chromatographic (HPLC) method has been developed and validated for simultaneous determination of ricobendazole (RBZ) and its main metabolite albendazole sulfone (ABZSO(2)) in sheep plasma using an isocratic system with UV detection. The method involved solid phase extraction followed by separation on a reversed phase C-18 column. Internal standard was selected by quantitative structure retention relationships (QSRRs) analysis. A method to optimize the composition of ternary components mobile phase with the assistance of multiple linear regression is described. Retention times were within 10 min. The calibration curves were linear over a concentration range of 10-1000 ng/ml for both RBZ and ABZSO(2) (r > 0.999). Intra-day relative standard deviation at low, medium and high concentration levels were <5.5% for RBZ and <4.6% for ABZSO(2); average accuracies were 98.3, 101.0 and 100.5% for RBZ and 101.0, 102.4 and 100.8% for ABZSO(2). The inter-day variations at the same concentrations were <5.9% for RBZ and <6.4% for ABZSO(2). The extraction recoveries at these concentrations for RBZ, ABZSO(2) and the internal standard were all over 96%. The limit of detection and limit of quantitation were 2.4 and 7.1 ng/ml, respectively for RBZ, and 10ng/ml for both analytes.

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.

Variation among faecal egg counts following natural nematode infection in Scottish Blackface lambs

Faecal egg counts were examined in 2 flocks of naturally infected Scottish Blackface sheep in southern and central Scotland. The distribution of mean counts was right skewed and similar to a gamma distribution. The counts varied with month, with mean counts rising from May to July, then falling but rising again in October, although data within each year did not always show such a clear pattern. There was no significant difference in mean egg count between the 2 farms examined. The distribution of egg count variances was also right skewed and conformed to a gamma distribution. There was a strong relationship between the mean and the variance for each population, implying that variation among populations in variances largely mirrored variation in mean egg counts. Populations with high mean egg counts and variances did not necessarily have more adult nematodes but had a greater number of adult nematodes from species other than Teladorsagia circumcincta, particularly Cooperia spp., Trichostrongylus axei and Trichostrongylus vitrinus. The contribution of different parasite species to the egg count explains the relatively poor and inconsistent fit of the negative binomial distribution to faecal egg counts in lambs.

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.

Highly sensitive ion pair liquid chromatographic determination of albendazole marker residue in animal tissues

A simple, rapid, and highly sensitive ion pair liquid chromatographic method for the determination of albendazole sulfoxide, albendazole 2-aminosulfone, and albendazole sulfone, which constitute the marker residue of albendazole in animal tissues (muscle, fat, liver, and kidney), is described. Tissue samples were extracted with acetonitrile, and the extracts were partitioned, as ion pairs, into dichloromethane. The organic layer was evaporated to dryness, and the residue was reconstituted in phosphate buffer and extracted with ethyl acetate. Separation was carried out isocratically with a mobile phase containing both positively and negatively charged pairing ions. Detection was performed fluorometrically, with excitation and emission wavelengths set at 290 and 320 nm, respectively. Overall recoveries were better than 76%, and the overall relative standard deviation was better than 7.3% in all tissues examined. The limits of quantification were 20, 1, and 0.5 ng/g for sulfoxide, 2-aminosulfone, and sulfone metabolites, respectively. The method was successfully applied to determine residues in tissues of two sheep orally administered an albendazole formulation.

Inhibitory effect of albendazole and its metabolites on cytochromes P450 activities in rat and mouflon in vitro

Cytochromes P450 (CYP) belong to the most important biotransformation enzymes, therefore, their inhibition may lead to serious pharmacological and toxicological consequences. Albendazole (ABZ) is a benzimidazole anthelmintic widely used in human and veterinary medicine. The effects of ABZ on CYP were investigated on the rat (Rattus norvergicus) and mouflon (Ovis musimon) hepatic microsomes. Besides ABZ, its two main metabolites (albendazole sulfoxide, ABZSO, and albendazole sulfone, ABZSOO) were tested to clarify which compound is responsible for the inhibitory effect. After preincubation of microsomes with the benzimidazoles (1, 5 and 25 microM), CYP activities, ethoxyresorufin O-deethylase (EROD) and benzyloxyresorufin O-dearylase activities were measured. The results showed that both ABZ and ABZSO, but not ABZSOO, exhibited significant potency to inhibit CYP activities measured in both tested species. Since ABZ as well as ABZSO are known inducers of EROD activity, our results clearly demonstrate that the drug can act as inducer and also as inhibitor of the same enzyme. In in vitro studies the CYP inhibition may mask the CYP induction. The extent of inhibition observed in mouflon was significantly higher than in rat. This finding emphasizes the importance of performance of inhibition studies in target animal species. Possible consequences of CYP inhibition should be taken into account during the anthelmintic therapy of mouflons with ABZ.

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.

Antitumor activity of albendazole against the human colorectal cancer cell line HT-29: in vitro and in a xenograft model of peritoneal carcinomatosis

The peritoneal surface remains an important failure site for patients with colorectal cancer. We have recently shown that albendazole (ABZ), a safe and effective anthelmintic drug, has profound antitumor activity in hepatocellular cancer. Furthermore, albendazole also possesses unique physiochemical and pharmacokinetic properties probably making it a potential drug for use in the regional treatment of peritoneal carcinomatosis (PC). The current study was therefore designed to investigate this concept under both in vitro and in vivo conditions using human colorectal cancer cells HT-29. In cell culture, studies were conducted to investigate the effect of ABZ and its major metabolites, albendazole sulfoxide (ABZ-SO) and albendazole sulfone (ABZ-SO2) on the growth of human colorectal cell line HT-29. We also investigated the effects of ABZ on the cell cycle and the possible induction of apoptosis in these cells. Male nude mice inoculated intraperitoneally (i.p.) with HT-29 cells were treated with various schedules of ABZ given i.p. or orally for 6 weeks. Response was evaluated as the number of peritoneal tumor nodules present in animals at the end of the treatment period. In vitro, ABZ treatment of cells for 5 days led to profound inhibition of growth. (3)H-Thymidine assay and trypan blue viable cell counts confirmed the dose- and time-dependency of the ABZ effect, while recovery experiments revealed the reversible nature of this inhibition. ABZ-SO and ABZ-SO2 were also evaluated in cell culture studies and compared with the parent drug. In HT-29 cells, the IC(50) values were calculated to be 0.12 microM for ABZ and 2.35 microM for ABZ-SO. The other metabolite, ABZ-SO2, was completely inactive. Studies on the mechanism of ABZ action, revealed arrest of HT-29 cells at the G(2)/M phase of the cell cycle, while TUNEL, DNA laddering and caspase-3 activity all confirmed ABZ induced apoptosis. In nude mice with peritoneal HT-29 xenografts, ABZ profoundly inhibited peritoneal tumor growth. While alternate i.p. dosing (ABZ, 150 mg/kg) led to the highest degree of tumor growth suppression (P<0.001), schedules such as once-weekly dosing and even a single dose for the entire course of treatment (6 weeks) were also effective in reducing peritoneal tumor growth. However, no such activity was observed when ABZ was administered orally. This study shows for the first time the potent effect of regionally administered ABZ in suppressing the growth of peritoneal tumors of human colorectal origin. The effect is thought to be brought about by arresting tumor cells at the G(2)/M phase of the cycle and apoptosis. These findings provide evidence for potential value of ABZ in the treatment of regional PC arising from colorectal cell lines.

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.

Quantitative determination of albendazole metabolites in sheep spermatozoa and seminal plasma by liquid chromatographic analysis with fluorescence detection

A new analytical method for the simultaneous quantitative determination of albendazole metabolites in sheep spermatozoa and seminal plasma at levels down to 46.5 ng/mL for albendazole sulphoxide (ABZ-SO), 7.5 ng/mL for albendazole sulphone (ABZ-SO2) and 12 ng/mL for albendazole 2-aminosulphone (ABZ-SO2NH2) has been developed. Analytes were extracted from alkalinized samples with ethyl acetate. Separation was carried out on a C18 column in the presence of tetra-n-butylammonium (TBA) hydrogen sulphate and octanesulphonate sodium (OCT), as ion-pair agents. Fluorometric detection was performed with excitation and emission wavelengths set at 290 and 320 nm, respectively. Accuracy data showed overall recoveries (+/-S.E.M.) of 83.1+/-1.2% for ABZ-SO, 98.8+/-0.6% for ABZ-SO2 and 85.3+/-0.7% for ABZ-SO2NH2, in spermatozoa. Respective values in seminal plasma were 88.0+/-0.9%, 97.7+/-0.5% and 93.2+/-1.7%. Precision data suggested coefficient of variation (CV%) values lower than 5.9% for spermatozoa and 3.8% for seminal plasma. The method was successfully applied for the determination of the three albendazole metabolites in semen samples collected from rams that had been orally administered albendazole.

Resistance to benzimidazole and macrocyclic lactone anthelmintics in cattle nematodes in Argentina

In April 2003, persistent scouring and ill-thrift that was reported in calves form an intensive beef rearing operation in central Argentina despite treatments with benzimidazole and ivermectin. In order to conduct a controlled faecal egg count reduction test on this herd, 40 calves 5-8-months-old were selected on the basis that they had a nematode eggs per gram (epg) of faeces count greater than 150. Animals were divided into four groups (1-4) of 10 calves. Calves of groups 1-3 were treated, respectively, with subcutaneous injection of ivermectin (200 mcg/kg), ricobendazole (4 mg/kg) and levamisole (7.5 mg/kg), while calves of group 4 remained as untreated controls. The egg count reductions carried out 10 days later were lower than 15% in calves treated with ivermectin and ricobendazole, but 100% in animals receiving levamisole. Pooled post-treatment faecal cultures showed larval percentages of 92 and 95 for Haemonchus and 8 and 5 for Cooperia in the faeces of calves treated with ivermectin and ricobendazole, respectively. This is the first reported case of Haemonchus parasiting cattle showing simultaneous resistance to avermectins and benzimidazole type anthelmintics.

Synthesis and antiparasitic activity of albendazole and mebendazole analogues

Albendazole (Abz) and Mebendazole (Mbz) analogues have been synthesized and in vitro tested against the protozoa Giardia lamblia, Trichomonas vaginalis and the helminths Trichinella spiralis and Caenorhabditis elegans. Results indicate that compounds 4a, 4b (Abz analogues), 12b and 20 (Mbz analogues) are as active as antiprotozoal agents as Metronidazole against G. lamblia. Compound 9 was 58 times more active than Abz against T. vaginalis. Compounds 8 and 4a also shown high activity against this protozoan. Compounds 4b and 5a were as active as Abz. None of the Mbz analogues showed activity against T. vaginalis. The anthelmintic activity presented by these compounds was poor.

Reversed-phase liquid chromatographic method with fluorescence detection for the simultaneous determination of albendazole sulphoxide, albendazole sulphone and albendazole 2-aminosulphone in sheep plasma

A rapid and sensitive HPLC method for the simultaneous quantification of albendazole sulphoxide (ABZ-SO), albendazole sulphone (ABZ-SO2) and albendazole 2-aminosulphone (ABZ-SO2NH2) in sheep blood plasma has been developed. Plasma samples were extracted with ethyl acetate under alkaline conditions. Separation was achieved on a C18 reversed-phase analytical column, in the presence of positively- (tetra-n-butylammonium hydrogen sulphate) and negatively-charged (octanesulphonate sodium) pairing ions, while detection was performed fluorometrically. Excitation and emission wavelengths were 290 and 320 nm, respectively. Limits of quantification were defined at 39 ng/ml for ABZ-SO, 4.95 ng/ml for ABZ-SO2 and 4 ng/ml for ABZ-SO2NH2. Accuracy data, in terms of recovery efficiency showed overall values (+/- S.E.M.) of 85.6 +/- 1.0% for ABZ-SO, 100.0 +/- 1.0% for ABZ-SO2 and 89.1 +/- 0.6% for ABZ-SO2NH2. The method was successfully applied to quantitatively determine the three albendazole metabolites in plasma samples collected from sheep that had been orally administered albendazole.

Monitoring of drugs and metabolites in body fluids by capillary electrophoresis with XeHg lamp-based and laser-induced fluorescence detection

Commercial capillary electrophoresis instrumentation with XeHg lamp-based and laser induced fluorescence (LIF) detection is employed for analysis of urinary 3,4-methylenedioxymethamphetamine (MDMA, Ecstasy) and its major metabolites, urinary metabolites of acetylsalicylic acid, urinary benzoylecgonine in an immunoassay format, and albendazole sulfoxide and albendazole sulfone in plasma. For the examples studied, the data suggest that the lamp-based detector can be employed for the monitoring of pharmacological and toxicological relevant solute concentrations, and thus represents an attractive alternative to LIF detection.

[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.

Effect of the ionophore antibiotic monensin on the ruminal biotransformation of benzimidazole anthelmintics

The benzimidazole (BZD) anthelmintics, netobimin (NTB) pro-drug and albendazole sulphoxide (ABZSO) are reduced to albendazole (ABZ) by ruminal microflora. The aim of the current work was to evaluate the influence of the ionophore monensin (MON) on the in vitro biotransformation of NTB and ABZSO by sheep ruminal fluid. Ruminal fluid, collected from Corriedale sheep, was preincubated (24 h) either without (control) or with known MON concentrations (0.5, 1.5 and 3.0 microg/mL) at 38 degrees C under a CO2 atmosphere. Afterwards, aliquots from both MON-pretreated and control ruminal fluid samples were incubated (30 and 60 min) with 2 microg/mL of either NTB or ABZSO. Incubated samples were chemically extracted and analysed by High Performance Liquid Chromatography to quantify the metabolites formed. The rate of ABZ production after 30 min of NTB incubation with control ruminal fluid was 0.023 microg/min. Conversely, the rates of ABZ formation were significantly (P<0.05) lower (0.009, 0.011 and 0.013 microg/min) when NTB was incubated with ruminal fluid pretreated with MON (at 0.5, 1.5 and 3.0 microg/mL, respectively). After both incubation periods, the reduction of ABZSO to ABZ was 22 to 70% lower when the ruminal fluid was preincubated with the different MON concentrations. The lower ABZ production observed in the presence of MON may result in a modified availability of this molecule in the gastrointestinal (GI) tract and hence, on its anthelmintic efficacy against GI nematodes.

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).

Effect of two formulations of benzimidazole carbamates on the viability of cysts of Echinococcus granulosus in vivo

Two different preparations, solution and suspension, of three benzimidazole carbamate drugs, mebendazole, albendazole and ricobendazole, were compared by analyzing their in vivo activity against Echinococcus granulosus cysts in a mouse model. Polyvinylpyrrolidone was used for the elaboration of drug solutions and these formulations manifested better results in terms of reduction of number of viable hydatid cysts in mice than the reference drug suspensions. The effect was more prominent on mebendazole-treated mice, at doses of 25-50 mg/kg. There was a correlation between ED50 and pharmacokinetical parameters of AUC0-infinity and Cmax, showing that a significant improvement on solubility affects the in vivo activity of these drugs.

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.

Albendazole sulphoxide concentrations in plasma of endemic normals from a lymphatic filariasis endemic region using liquid chromatography

A simple and sensitive reversed-phase isocratic HPLC method for the determination of albendazole and its metabolites has been developed. The mobile phase consisting of acetonitrile-water-perchloric acid (70%) (30:110:0.06 (v/v/v)) was pumped at a flow rate of 0.80 ml/min on a 5 microm, reverse phase, Discovery RPamide C16 column with UV detection at 290 nm. The calibration graphs were linear in the range of 0.05- 1 microg/ml for albendazole, albendazole sulphoxide and albendazole sulphone. The limit of quantification was 50 ng/ml for albendazole, 25 ng/ml for albendazole sulphoxide and 30 ng/ml for albendazole sulphone. The within-day and day-to-day coefficient of variation averaged 4.98 and 6.95% for albendazole, 3.83 and 6.83% for albendazole sulphoxide and 3.44 and 5.51% for albendazole sulphone, respectively. The mean extraction recoveries of albendazole, albendazole sulphoxide and albendazole sulphone were 79.25, 93.03 and 88.78%, respectively. The method was applied to determine the plasma levels of albendazole sulphoxide in endemic normals administered with albendazole during pharmacokinetic studies.

Aspects of the pharmacokinetics of albendazole sulphoxide in sheep

The plasma disposition kinetics of albendazole sulphoxide (ABZSO), ((+)ABZSO and (-)ABZSO) and its sulphone metabolite (ABZSO2) were investigated in adult sheep. Six Corriedale sheep received albendazole sulphoxide by intravenous injection at 5 mg/kg live weight. Jugular blood samples were taken serially for 72 h and the plasma was analysed by high-performance liquid chromatography (HPLC) for albendazole (ABZ), ABZ sulphoxide (ABZSO) and albendazole sulphone (ABZSO2). Albendazole was not detected in the plasma at any time after the treatment, ABZSO and ABZSO2 being the main metabolites detected between 10 min and 48 h after treatment. A biexponential plasma concentration versus time curve was observed for both ABZSO and ABZSO2 following the intravenous treatment. The plasma AUC values for ABZSO and ABZSO2 were 52.0 and 10.8 (microg x h)/ml, respectively. The ABZSO2 metabolite was measurable in plasma between 10 min and 48 h after administration of ABZSO, reaching a peak concentration of 0.38 microg/ml at 7.7 h after treatment. Using a chiral phase-based HPLC method, a biexponential plasma concentration versus time curve was observed for both ABZSO enantiomers. The total body clearance was higher for the (-) than for the (+) enantiomer, the values being 270.6 and 147.75 (ml/h)/kg, respectively. The elimination half-life of the (-) enantiomer was shorter than that of the (+) enantiomer, the values being 4.31 and 8.33 h, respectively. The enantiomeric ratio (+)ABZSO/( )ABZSO at t0 was close to unity. However, the ratio in the plasma increased with time.

The effects of albendazole and its metabolites on hepatic cytochromes P450 activities in mouflon and rat

Albendazole (ABZ) is a benzimidazole anthelmintic widely used in veterinary medicine. The effects of ABZ on cytochromes P450 were investigated in primary cultures of mouflon (Ovis musimon) and rat (Rattus norvegicus) hepatocytes. Besides ABZ, its two main metabolites (albendazole-sulphoxide, ABZSO and albendazole-sulphone, ABZSOO) were tested to clarify which compound is responsible for the induction potency of this benzimidazole drug. After 48 h incubation of hepatocytes with benzimidazoles (0.2-25 microM), ethoxyresorufin O-deethylation (EROD) and benzoxyresorufin O-dearylation (BROD) were measured and the P4501A and 3A protein levels were determined by Western blotting. All benzimidazoles provoked a significant increase of EROD and BROD activities in rat hepatocytes. ABZSO and ABZSOO seemed to be responsible for the induction effect of ABZ on P450s in rat. In mouflon, no pharmacologically significant induction of EROD and BROD activities by benzimidazoles tested was observed. From this point of view, anthelmintic therapy of mouflons with ABZ seems to be safe.