Rapid and Sensitive Drug Quantification in Tissue Sections Using Matrix Assisted Laser Desorption Ionization-Ion Mobility-Mass Spectrometry Profiling

Ion mobility spectrometry (IMS) represents a considerable asset for analytics of complex samples as it allows for rapid mass spectrometric separation of compounds. IMS is even more useful for the separation of isobaric compounds when classical separation methods such as liquid chromatography or electrophoresis cannot be used, e.g., during matrix-assisted laser desorption/ionization (MALDI) analyses of biological surfaces. In the present study, we proved the usefulness of IMS for pharmacological applications of MALDI analyses on tissue sections. To illustrate our proof-of-concept, we used the anthelmintic drug mebendazole (MBZ) as a model. Using this exemplary drug, we demonstrated the possibility of using ion mobility to discriminate a drug in tissues from the biological background that masked its signal at low concentrations. In this proof-of-concept, the IMS mode together with the use of a profiling approach for sample preparation enabled quantification of the model drug MBZ from tissue sections in the concentration range 5 to 5,000 ng/g and with a limit of detection of 1 ng/g of tissue, within 2 h. This study highlights the importance of IMS as a separation method for on-surface quantification of drugs in tissue sections.

Macrofilaricidal efficacy of single and repeated oral and subcutaneous doses of flubendazole in Litomosoides sigmodontis infected jirds

Flubendazole (FBZ) is highly efficacious against filarial nematodes after parenteral administration and presents a promising macrofilaricidal drug candidate for the elimination of onchocerciasis and other filariae. In the present study the efficacy of a newly developed bioavailable amorphous solid dispersion (ASD) oral formulation of FBZ was investigated in the Litomosoides sigmodontis jird model. FBZ was administered to chronically infected, microfilariae-positive jirds by single (40mg/kg), repeated (2, 6 or 15mg/kg for 5 or 10 days) oral (OR) doses or single subcutaneous (SC) injections (2 or 10mg/kg). Jirds treated with 5 SC injections at 10mg/kg served as positive controls, with untreated animals used as negative controls. After OR doses, FBZ is rapidly absorbed and cleared and the exposures increased dose proportionally. SC administered FBZ was slowly released from the injection site and plasma levels remained constant up to necropsy eight weeks after treatment end. Increasing single SC doses caused less than dose-proportional exposures. At necropsy, all animals receiving 1x or 5x 10mg/kg SC FBZ had cleared all adult worms and the 1x 2mg/kg SC treatment had reduced the adult worm burden by 98%. 10x 15mg/kg OR FBZ reduced the adult worm burden by 95%, whereas 1x 40mg/kg and 5x 15mg/kg OR reduced the worm burden by 85 and 84%, respectively. Microfilaremia was completely cleared at necropsy in all animals of the SC treatment regimens, while all oral FBZ treatment regimens reduced the microfilaremia by >90% in a dose and duration dependent manner. In accordance, embryograms from female worms revealed a FBZ dose and duration dependent inhibition of embryogenesis. Histological analysis of the remaining female adult worms showed that FBZ had damaged the body wall, intestine and most prominently the uterus and uterine content. Results of this study demonstrate that single and repeated SC injections and repeated oral administrations of FBZ have an excellent macrofilaricidal effect.

Onchocerciasis and lymphatic filariasis are debilitating human diseases that are caused by filarial nematodes leading to blindness and severe dermatitis (onchocerciasis) or lymphedema (elephantiasis) and hydroceles. Current mass drug administration (MDA) programs are restricted to the use of drugs that target the filarial offspring, the microfilariae, and lead to a temporary sterilization of the female adult worms that requires annual to bi-annual MDA for the life span of the fertile adult worms. With lower endemicity, the cost-effectiveness of community-directed MDA is reduced, requiring alternative treatment strategies to ultimately eliminate these filarial infections. Therefore, new drugs targeting the adult worms are required for achieving elimination of those filarial diseases, to provide options in areas of drug resistance, and as an approach in areas of Loa loa co-endemicity, where life-threatening severe adverse events may occur through the use of microfilaricidal drugs. Such new drugs should have a macrofilaricidal effect, i.e. kill the adult worms or lead to a permanent sterilization. Furthermore, these drugs should be preferably administered as an oral formulation or by a single parenteral administration. In the current study we tested a new oral formulation of flubendazole using the rodent filarial nematode Litomosoides sigmodontis, and have demonstrated excellent macrofilaricidal efficacy.

Preclinical toxicity and pharmacokinetics of a new orally bioavailable flubendazole formulation and the impact for clinical trials and risk/benefit to patients

BACKGROUND

Flubendazole, originally developed to treat infections with intestinal nematodes, has been shown to be efficacious in animal models of filarial infections. For treatment of filarial nematodes, systemic exposure is needed. For this purpose, an orally bioavailable amorphous solid dispersion (ASD) formulation of flubendazole was developed. As this formulation results in improved systemic absorption, the pharmacokinetic and toxicological profile of the flubendazole ASD formulation have been assessed to ensure human safety before clinical trials could be initiated.

METHODS & FINDINGS

Safety pharmacology, toxicity and genotoxicity studies have been conducted with the flubendazole ASD formulation. In animals, flubendazole has good oral bioavailability from an ASD formulation ranging from 15% in dogs, 27% in rats to more than 100% in jirds. In in vivo toxicity studies with the ASD formulation, high systemic exposure to flubendazole and its main metabolites was reached. Flubendazole, up to high peak plasma concentrations, does not induce Cmax related effects in CNS or cardiovascular system. In repeated dose toxicity studies in rats and dogs, flubendazole-induced changes were observed in haematological, lymphoid and gastrointestinal systems and in testes. In dogs, the liver was an additional target organ. Upon treatment cessation, at least partial recovery was observed for these changes in dogs. In rats, the No Observed Adverse Effect Level (NOAEL) was 5 mg (as base)/kg body weight/day (mg eq./kg/day) in males and 2.5 mg eq./kg/day in females. In dogs, the NOAEL was lower than 20 mg eq./kg/day. Regarding genotoxicity, flubendazole was negative in the Ames test, but positive in the in vivo micronucleus test.

CONCLUSIONS

Based on these results, in combination with previously described genotoxicity and reproductive toxicity data and the outcome of the preclinical efficacy studies, it was concluded that no flubendazole treatment regimen can be selected that would provide efficacy in humans at safe exposure.

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.

Exploring the potential of flubendazole in filariasis control: evaluation of the systemic exposure for different pharmaceutical preparations

The goal of elimination of the human filariases would benefit greatly from the use of a macrofilaricidal agent. In vivo trials in humans and many experimental animal models suggest that flubendazole (FLBZ) is a highly efficacious macrofilaricide. However, since serious injection site reactions were reported in humans after parenteral FLBZ administration, the search for alternative pharmaceutical strategies to improve the systemic availability of FLBZ and its metabolites has acquired urgency in both human and veterinary medicine. The goal of the current work was to compare the systemic exposure of FLBZ formulated as either an aqueous hydroxypropyl-β-cyclodextrin (CD) or aqueous carboxymethyl cellulose (CMC) suspension or a Tween 80-based formulation (TWEEN) in rats and jirds (Meriones unguiculatus). Healthy animals of both species were allocated into four experimental groups of 44 animals each: FLBZ-CD_oral and FLBZ-CD_sc, treated with the FLBZ-CD formulation by the oral or subcutaneous routes, respectively; FLBZ-TWEEN_sc, dosed subcutaneously with the FLBZ-TWEEN formulation; and FLBZ-CMC_oral, treated orally with the FLBZ suspension. The FLBZ dose was 5 mg/kg. FLBZ and its hydrolyzed (H-FLBZ) and reduced (R-FLBZ) metabolites were recovered in plasma samples collected from rats and jirds treated with the different FLBZ formulations. In both species, FLBZ parent drug was the main analyte recovered in the bloodstream. In rats, FLBZ systemic exposure (AUC_0-LOQ) was significantly (P<0.05) higher after the FLBZ-CD treatments, both oral (4.8±0.9 µg.h/mL) and subcutaneous (7.3±0.6 µg.h/mL), compared to that observed after oral administration of FLBZ-CMC suspension (0.93±0.2 µg.h/mL). The same differences were observed in jirds. In both species, parenteral administration of FLBZ-TWEEN did not improve the systemic availability of FLBZ compared to FLBZ-CD_oral treatment. In conclusion, formulation approaches that enhance the availability of flubendazole in the rat and jird may have therapeutic implications for a drug with poor or erratic bioavailability.

Lymphatic filariasis and onchocerciasis are tropical parasitic diseases caused by filarial nematodes, which constitute a serious public health issue in tropical regions. Lymphatic filariasis causes debilitating lymphedema and hydrocele, resulting in temporary or permanent disability. Onchocerciasis (also known as river blindness) causes visual impairment and blindness, constituting one of the leading causes of blindness in the world. The control of human filarial infections currently depends on strategies predominantly focused at killing microfilariae (larval stage) by the use of ivermectin or diethylcarbamzine, usually in combination with albendazole. It is now generally recognized that the success of filariasis control programs in a reasonable time-frame requires the addition of a macrofilaricide (adult stage) compound. Although flubendazole has demonstrated macrofilaricidal activity in vivo, the approved formulations provide almost no oral bioavailability. The search for alternative pharmaceutical strategies to improve the systemic availability of flubendazole has acquired urgency in both human and veterinary medicine. Searching for improved flubendazole absorption, different flubendazole pharmaceutical preparations were assessed, both in rats and jirds, in the study described here. The work demonstrated that flubendazole pharmacokinetics could be markedly modified by changes in drug formulation. The resulting improved systemic exposure of flubendazole may have a significant impact on its macrofilaricidal efficacy.

Development and in vitro characterization of mebendazole delayed release tablet for colonic drug delivery

The main objective behind this study was to formulate delayed release colon targeted tablet of Mebendazole by using different polymers. The precompressional parameters of powder blend were studied. The wet granulation method was used for the preparation of tablets. The tablets of all formulation were subjected for different physicochemical evaluation. The drug-excipient interaction study was carried out by using Fourier transforms Infrared spectroscopy (FTIR). The in vitro evaluation was carried out at different pH ranges (0.1M HCl, 6.8 and 7.4 Phosphate buffer) for the prepared tablets. From the stability, Fourier transform infra-red spectroscopy studies Mebendazole tablet does not show any interaction between drug and polymer. The prepared tablets were complied all the physicochemical test as per official limit. The formulated (M3) batch shows better sustained release 99.89% over a period of 12 hours and the data was fitted into Korsemeyer-Peppas kinetic equation. The result indicates that Mebendazole colon targeted matrix tablet remain stable in the stomach and shows better release into the colon with the help of pH dependent synthetic polymers.

Distribution and depletion of flubendazole and its metabolites in edible tissues of guinea fowl

1. We measured the distribution and depletion of residues of flubendazole and its major metabolites in breast muscle, thigh muscle and liver of guinea fowls during and after oral administration of the veterinary medicine Flubenol 5% at two doses. 2. The guinea fowls were treated orally with normal feed, medicated at doses of 56 and 86 mg per kg feed for 7 successive days. Afterwards, depletion was observed for 8 d. Just before slaughter, body weights were measured. Thigh muscle, breast muscle and liver of three female and three male birds were sampled. The concentrations of the flubendazole-derived residues were determined by a liquid chromatographic-mass spectrometric method. 3. The highest residue concentrations were obtained for the reduced metabolite. With the therapeutic dose, the maximum mean residue concentrations obtained for this compound in thigh muscle, breast muscle and liver were 312, 288 and 1043 microg/kg, respectively. The values for flubendazole, the parent molecule, were 114, 108 and 108 microg/kg, respectively. The residues of the hydrolysed metabolite were negligible in the sampled muscle tissues. After 24 h of depletion, the sum of the residues of parent and metabolites in muscle tissue still exceeded 50 microg/kg. After 8 d of depletion, flubendazole-derived residues at low concentrations could still be measured in both muscle tissues and liver. Generally, the disposition of residues in breast and thigh muscle was comparable. 4. The European Union has not established a maximum residue limit (MRL) for flubendazole in edible tissues of guinea fowl. In contrast, the existing MRLs for other bird species are expressed as the sum of parent flubendazole and its hydrolysed metabolites. An estimated withdrawal period of three days will assure residue safety in the edible tissues of guinea fowl treated with flubendazole at therapeutic dose. After this withdrawal period following treatment of the guinea fowl, the residues were approximately constant, very low and far below the established safe MRL level for other bird species.

[Research progress on the efficacy, metabolism and bioavailability of mebendazole in hydatid disease]

Mebendazole is currently used in the treatment of hydatid disease. Its poor absorption from the gastrointestinal tract and low bioavailability aroused further research on new formulations of mebendazole to increase the bioavailability and improve the therapeutic efficacy. This review summarizes the recent research progress.

Integrated pharmacological assessment of flubendazole potential for use in sheep: disposition kinetics, liver metabolism and parasite diffusion ability1

Flubendazole (FLBZ) is a broad spectrum benzimidazole methylcarbamate anthelmintic widely used in poultry and swine. However, there is no information available on the pharmacological behaviour of FLBZ in ruminants. The work reported here was addressed to evaluate the potential of FLBZ for use in sheep. The integrated assessment included evaluation of FLBZ and metabolites plasma disposition kinetics, liver metabolism and ex vivo ability to diffuse into the cestode parasite Moniezia benedeni. In a cross-over kinetic study, six healthy Corriedale sheep were treated with FLBZ by intravenous (i.v.) (4% solution) and intraruminal (i.r.) (4% suspension) administrations at the same dosage (5 mg/kg) with a 21-day washout period between treatments. Blood samples were collected between 0 and 72 h post-treatments. Sheep liver microsomes were incubated with 40 microm FLBZ and specimens of the cestode parasite M. benedeni, collected from untreated animals, were incubated (5-120 min) with FLBZ and its reduced (R-FLBZ) metabolite (5 microm). Samples of plasma, microsomal incubations and parasite material were prepared and analyzed by high-performance liquid chromatography to measure FLBZ and its metabolites. FLBZ parent drug showed a fast disposition being detected in the bloodstream up to 36 h after its i.v. administration. Both R-FLBZ and hydrolyzed FLBZ (H-FLBZ) metabolites were recovered in plasma as early as 5 min after the i.v. treatment in sheep. The plasma AUC ratios for R-FLBZ and FLBZ (AUC(R-FLBZ)/AUC(FLBZ)) were 4.07 i.v. and 5.55 i.r., respectively. R-FLBZ achieved a significantly higher (P < 0.01) C(max) value (0.14 microg/mL at 17.3 h post-treatment) than that observed for the parent drug FLBZ (0.04 microg/mL at 14.4 h post-treatment). Low plasma concentrations of FLBZ parent drug were measured between 6 and 48 h, and only trace concentrations of H-FLBZ were detected during a short period of time after the i.r. treatment. Consistently, sheep liver microsomes metabolized FLBZ into its reduced metabolite at a rate of 9.46 +/- 2.72 nmol/mg/h. Both FLBZ and R-FLBZ demonstrated a similar ability to quickly diffuse through the tegument of the cestode parasite. The data on FLBZ pharmacological behaviour presented here contribute to evaluate its potential to be developed as an anthelmintic for broad spectrum parasite control in ruminants.

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, mebendazole and praziquantel. Review of non-clinical toxicity and pharmacokinetics

The pharmacokinetics and toxicity of albendazole, mebendazole and praziquantel are extensively reviewed, drawing on original published work and reviews in the open scientific literature and on assessments by international agencies and official regulatory bodies in Europe and the USA. Information about human and veterinary medical uses and adverse reactions is evaluated. The totality of the non-clinical information available about these long-established drugs may not comply with current official guidelines for new medicines but reasons are given why the "deficiencies" are only apparent and the data gaps can be replaced by other results, largely obtained from the target species and the many years of clinical experience of safe use of these drugs in humans and animals.

Pharmacokinetic evaluation of guar gum-based colon-targeted drug delivery systems of mebendazole in healthy volunteers

The pharmacokinetic evaluation of guar gum-based colon-targeted tablets of mebendazole against an immediate release tablet was carried out in human volunteers. Six healthy volunteers participated in the study and a crossover design was followed. Mebendazole was administered at a dose of 50 mg both in immediate release tablet and colon-targeted tablets. On oral administration of colon-targeted tablets, mebendazole started appearing in the plasma at 5 h, and reached the peak concentration (C(max) of 25.7+/-2.6 ng/ml) at 9.4+/-1.7 h (T(max)) whereas the immediate release tablets produced peak plasma concentration (C(max) of 37.2+/-6.8 ng/ml) at 3.4+/-0.9 h (T(max)). Colon-targeted tablets showed delayed t(max) and absorption time, and decreased C(max) and absorption rate constant when compared to the immediate release tablets. The results of the study indicated that the guar gum-based colon-targeted tablets of mebendazole did not release the drug in stomach and small intestine, but delivered the drug to the colon resulting in a slow absorption of the drug and making the drug available for local action in the colon.

In vitro studies on the effects of flubendazole against Toxocara canis and Ascaris suum

Adult Toxocara canis and Ascaris suum were incubated in vitro in media containing 0.1, 1, 10 or 100 micro g/ml flubendazole in order to study drug-derived effects. This incubation was done for 8 h and repeated (in some groups) after 24 h for another 8 h. The onset and intensity of flubendazole-derived effects were dosage-dependent and time-dependent, i.e. the same grade of damage was reached when incubating for a longer period at a low dosage or for a shorter period in medium containing a high amount (10 or 100 micro g/ml) of flubendazole. A repeated incubation in drug-containing medium was superior to a single exposure. Flubendazole is apparently able to penetrate into the worm's interior via the cuticle. This became evident in worms with sealed orifices, which showed identical damage to worms which were not sealed. The type of tissue damage due to flubendazole was identical in both worm species when exposed to any of the drug dosages used. The principal mode of action of flubendazole was based on the complete reduction of microtubuli-polymerisation inside the parasite's cells. This apparently led to the complete destruction of the hypodermis, muscle layer and intestine. Flubendazole also stopped the formation of gametes. Summarising, even low concentrations of flubendazole (0.1 micro g/ml) led to significant and irreversible damage in all worms studied.

Determination of flubendazole and its metabolites in eggs and poultry muscle with liquid chromatography-tandem mass spectrometry

The optimization of a quantitative and sensitive LC-MS/MS method to determine flubendazole and its hydrolyzed and reduced metabolites in eggs and poultry muscle is described. The benzimidazole components were extracted from the two matrices with ethyl acetate after the sample mixtures had been made alkaline. The HPLC separation was performed on an RP C-18 column with gradient elution, using ammonium acetate and acetonitrile as mobile phase. The analytes were detected after atmospheric pressure electrospray ionization on a tandem quadrupole mass spectrometer in MS/MS mode. The components were measured by the MS/MS transition of the molecular ion to the most abundant daughter ion. The overall extraction recovery values for flubendazole, the hydrolyzed metabolite, and the reduced metabolite in eggs (fortification levels of 200, 400, and 800 microg kg(-1)) and muscle (fortification levels of 25, 50, and 100 microg kg(-1)) were, respectively, 77, 78, and 80% and 92, 95, and 90%. The trueness (fortification levels of 400 and 50 microg kg(-1), respectively, for eggs and muscle), expressed as a percentage of the added values for these analytes, was, respectively, 89, 100, and 86 and 110, 110, and 98%. The proposed MS detection method operating in the MS/MS mode is very selective and very sensitive. The limits of detection for flubendazole and its hydrolyzed and reduced metabolites in egg and muscle were, respectively, 0.19, 0.29, and 1.14 microg kg(-1) and 0.14, 0.75, and 0.31 microg kg(-1). The limits of quantification were, respectively, 1, 1, and 2 microg kg(-1) and 1, 1, and 1 microg kg(-1). The discussed method was applied to a pharmacokinetic study with turkeys. Residue concentrations in breast and thigh muscle of turkeys orally treated with flubendazole were quantified. Medicated feed containing 19.9 and 29.6 mg kg(-1) flubendazole was provided to the turkeys for seven consecutive days. For the trial with the recommended dose of 19.9 mg kg(-1), one day after the end of the treatment, the mean sum of the flubendazole plus hydrolyzed metabolite residue values in thigh and breast muscle declined to below the maximum residue limit (50 microg kg(-1)) and were, respectively, 36.6 and 54.1 microg kg(-1). The corresponding values with the higher dose of 29.6 mg kg(-1) were, respectively, 101.7 and 119.7 microg kg(-1).

Pharmacokinetics of UMF-078, a candidate antifilarial drug, in infected dogs

The pharmacokinetics of the filaricidal benzimidazole compounds UMF-078 and UMF-289 were evaluated in beagle dogs experimentally infected with Brugia pahangi. Twenty-four infected microfilaremic beagles were selected and randomly allocated into 4 treatment groups of 6 dogs each: oral (PO) UMF-078, PO UMF-289 (the HCl salt form of UMF-078), intramuscular (IM) UMF-078, and untreated controls. Equivalent doses of 50 mg/kg of the free base were given twice a day for 3 days to the 3 groups of treated dogs. Oral absorption is rapid compared with IM dosing; the absorption half-life (K01-HL) for the IM treatment is approximately 14 hr compared with 1 and 2 hr for the PO regimen of salt and free base forms, respectively. The elimination half-lives (K10-HL) for the PO regimens are 13 and 15 hr for the salt and free base forms, respectively. Because of sustained absorption following IM dosing, the K10-HL is prolonged. In contrast to oral administration, IM dosing of UMF-078 provides sustained, relatively low plasma drug levels, with good tolerance and efficacy.

Residue study of mebendazole and its metabolites hydroxy-mebendazole and amino-mebendazole in eel (Anguilla anguilla) after bath treatment

Mebendazole (MBZ) is extensively used in eel culture for treatment of Pseudodactylogyrus spp. infections. This use may lead to residues of MBZ in eel tissues. Consequently, the residue profile of MBZ in eel after treatment with the drug is of special concern. Therefore, a residue study was performed in European eels (Anguilla anguilla), bath-treated with MBZ at a dose of 1 mg/liter for 24 hr and kept at a water temperature of 25 degrees C. Liver, kidney, fat, skin, and muscle tissues samples were collected at intervals during and after treatment and analyzed for MBZ and its metabolites, hydroxy-MBZ (MBZ-OH) and amino-MBZ (MBZ-NH2), by HPLC. Results showed that MBZ is extensively metabolized to MBZ-OH and MBZ-NH2. Liver and kidney were found to contain the highest levels of MBZ metabolites, and fat contained the highest levels of the parent compound. Skin contained higher residue levels for all three compounds, compared with muscle tissue. MBZ and its hydroxy metabolite were eliminated within 5 days from the edible parts (muscle and skin) of the eels, whereas MBZ-NH2 could be detected by the 14th day after the end of the treatment period. Consequently, although MBZ and MBZ-OH constitute the residues of toxicological concern, MBZ-NH2 should be taken as the compound of interest for estimating the withdrawal time for consumption of eel treated with MBZ.

Fasciola hepatica: mebendazole and thiabendazole pharmacokinetics in sheep

Pharmacokinetics of the two anthelmintic drugs mebendazole and thiabendazole were determined in sheep before and 4, 8, 13, 19, and 25 weeks after an infestation of animals by an oral administration of 150 metacercariae of Fasciola hepatica. The parasitic pathology was ascertained by the increase in plasma enzyme activities of glutamate dehydrogenase and gamma-glutamyltransferase. After oral administration of mebendazole (25 mg.kg-1), the parent drug and especially its reduced metabolite were present in plasma of animals. A significant 1.5- to 2.7-fold increase in the mean residence time occurred by Weeks 13 to 25 postinfection. This change was related to decreases in both the elimination from the pharmacokinetic compartment representing the reduced metabolite and the area under the curve of plasma metabolite concentration versus time. A 59% decrease in MBZ reduction was demonstrated in liver microsomes prepared from 12-week-infected sheep. This reductase activity was characterized by NADPH dependency and a pH peak activity of 6.0 and was competitively inhibited by daunomycin. In sheep receiving a 50 mg.kg-1 oral dose of thiabendazole, fascioliasis provoked only decreased plasma concentrations of the metabolite 5-hydroxythiabendazole by Weeks 4 to 25 postinfection. This change parallels an increase in urinary excretion of free metabolite but this is of minor significance in the general fate of the drug because of the prevalence of excretion as conjugates. In summary, fascioliasis appears to have more of an effect on the pharmacokinetics of mebendazole, a drug intensively metabolized by the liver into a metabolite present at high concentrations in the plasma of animals and humans.

Influence of ethanol on gastric absorption and metabolism of albendazole and mebendazole

The effect of ethanol administration on gastric absorption in rats of two benzimidazole derivatives has been studied. The ethanol administration was carried out as both acute (5%, 10% and 15% w/v of ethanol in the perfusion solution), and chronic (15, 30 and 120 days) forms. Two benzimidazole derivatives were used: albendazole (ABZ) and mebendazole (MBZ). The administration of ethanol did not affect the kinetic mechanism of the absorption process (simple diffusion) but the absorption rate decreased in all treatments except in 5% acute ethanol, presumably due to the improved solubility of the drugs. Plasma, bile and liver levels after gastric perfusion suggest a possible interference of ethanol metabolism with drug hepatic metabolism.

Determination of the antifilarial drug UMF-078 and its metabolites UMF-060 and flubendazole in whole blood using high-performance liquid chromatography

A rapid and selective high-performance liquid chromatographic (HPLC) method for the simultaneous determination of the antifilarial drug UMF-078 (I) and its metabolites UMF-060 (II) and flubendazole (III) is described. After a simple extraction from whole blood, the compounds were determined by HPLC using a C18 Inertsil ODS-2 reversed-phase column with methanol-0.05M ammonium acetate (pH 4.0) as the mobile phase and ultraviolet detection at 291 nm. The average recoveries of I, II and III over the concentration range 20-500 ng ml-1 were 69.9 +/- 4.7, 85.6 +/- 4.4 and 85.1 +/- 6.0%, respectively. The minimum detectable concentrations in whole blood for I, II and III were 10, 7 and 7 ng ml-1, respectively. This method was found to be suitable for pharmacokinetic studies.

Determination of a new antifilarial drug, UMF-058, and mebendazole in whole blood by high-performance liquid chromatography

A rapid and selective high-performance liquid chromatographic assay for simultaneous quantitative determination of a new antifilarial drug (UMF-058, I) and mebendazole (MBZ) is described. After a simple extraction from whole blood, both compounds were analysed using a C18 Nova Pak reversed-phase column and a mobile phase of methanol-0.05 M ammonium dihydrogenphosphate (50:50, v/v) adjusted to pH 4.0, with ultraviolet detection at 291 nm. The average recoveries of I and MBZ over a concentration range of 25-250 ng/ml were 92.0 +/- 7.7 and 84.4 +/- 4.4%, respectively. The minimum detectable concentrations in whole blood for I and MBZ were 7 and 6 ng/ml, respectively. This method was found to be suitable for pharmacokinetic studies.

[The enhanced bioavailability of mebendazole in echinococcosis patients when used with Essentiale]

Mebendasole is better absorbed in the gastrointestinal tract if administered together with essential to patients with hydatid disease. Thirty-four patients with alveolar and hydatid echinococcosis were administered mebendasol in a daily dose of 50 mg/kg in 4 doses and essentiale in a daily dose of 600-1000 mg in 4 doses. A total of 86 therapeutic courses, 30 days each, were carried out. The treatment was sufficiently well tolerated. Mebendasole levels in the course of therapy surpassed the minimal effective ones in 2/3 of the patients, that is, they were significantly higher than in administration of mebendasole alone.

Albendazole and mebendazole uptake by isolated enterocytes

Uptake of albendazole (ABZ) and mebendazole (MBZ) by isolated rat enterocytes was carried out. These drugs, widely used oral anthelmintics, exhibit a scarce water solubility which reduce its absorption by the oral tract. The present study was designed to assess the captation for ABZ and MBZ in different enterocyte populations isolated from upper to crypt villus. The concentration range used for the absorption experiments was within 10-500 microM for both drugs, using DMSO as solvent. The results obtained show the existence of a passive mechanism for the uptake of ABZ and MBZ at concentrations between 10 and 100 microM, with a maximum intake value around 20 microM/mg protein. No differences were found with respect to the cell populations analyzed. The drug uptake levels seem to be higher for MBZ than for ABZ prior to reaching the maximum plateau.

Investigations on the biotransformation of mebendazole using an isolated perfused rat gut system

1. The intestinal metabolism of the benzimidazole, mebendazole (MEB), has been investigated using isolated perfused jejunal segments of rats. Significant absorption and intestinal metabolism of the substance was observed. 2. The metabolites, the reduced alpha-hydroxy-analogue, its glucuronide, and the decarbamoylated 2-amino-analogue, were transported into the resorbate collected at the serosal side or were resecreted into the gut lumen. 3. The intestinal decarbamoylation of mebendazole increased up to 20-fold after pretreatment with 3-methylcholanthrene (MC), and complete re-secretion of this metabolite into the gut lumen led to a total loss of the absorption of mebendazole and metabolites across the gut wall. 4. The results indicate the ability of the gut to metabolize mebendazole by phase I and II reactions. 5. An almost complete loss of bioavailability after induction of the gut enzyme system by MC was observed.

[Pharmacokinetics of four benzimidazoles administered intragastrically to mice infected with secondary cysts of Echinococcus granulosus]

Mice infected with secondary cysts of Echinococcus granulosus were treated ig with mebendazole (Meb), albendazole (Alb), albendazole sulfoxide (AlbSO) or albendazole sulphone (AlbSP) at equal effective dosage. The blood concentrations-time courses of the four drugs were adequately fitted to a liner one-compartment open model analysed with a modified NONLIN program, and the major pharmaco- kinetic parameters were then calculated (Table 1). When Alb was given ig to the infected mice, 76.2-84.5% of the drug absorbed was metabolized to AlbSO. There fore, the pharmacokinetics of AlbSO in Alb group was determined. After ig administration of Meb to the infected mice, the ratio of the drug contents in cyst wall to corresponding plasma concentrations of Meb was 10.6-26.9%, but much less in cyst fluid. In Alb and AlbSO groups, similar AlbSO contents in cyst wall and cyst fluid with higher ratio to plasma concentrations were observed (Fig 3). The results suggest that E granulosus cysts were more susceptible to Meb than to Alb or AlbSO, and improvement of Meb absorption would be favourable for enhancement of efficacy in the treatment of hydatid disease.

Improvement of dissolution and bioavailability for mebendazole, an agent for human echinococcosis, by preparing solid dispersion with polyethylene glycol

The solid dispersion of mebendazole was prepared with polyethylene glycol (PEG) to enhance the dissolution rate of mebendazole, an agent for the chemotherapy of human echinococcosis. The dissolution rate of the solid dispersion increased compared with the physical mixture, and also increased with the incorporation of an increasing amount of PEG-6000. An extensive improvement of the dissolution rate was observed when the ratio of the solid dispersion of mebendazole to PEG-6000 was more than 1: 2. Furthermore, greater bioavailability in rabbits was obtained after oral administration of the solid dispersion compared with the physical mixture.

[Uptake and release of mebendazole, albendazole and albendazole sulfoxide by secondary cysts of Echinococcus granulosus in vitro]

Mebendazole (Meb), albendazole (Alb) or albendazole sulfoxide (AlbSO) were taken rapidly in vitro by secondary cysts of Echinococcus granulosus removed out from mice infected with protoscoleces 8-9 months previously. The amounts of the drugs taken by the cysts were apparently increased followed by exposure of the cysts to the drugs at 10 micrograms.ml-1. The Alb penetrated into the cysts was distributed mainly in cyst wall, whereas the content of Meb in cyst wall was twice as much as that in cyst fluid. The distributions of AlbSO in cyst wall and cyst fluid were similar. When the cysts in the medium were exposed to Alb, some AlbSO and albendazole sulphone were detected in both cyst wall and cyst fluid, indicating that a part of Alb was metabolized by the cysts. In another experiment cysts exposed to the drug for 2 h were transferred to the medium without the drug for another 24 h. The release rates of the 3 drugs from the cysts were alike. In 1-2 h after transfer about 65-70% of the drugs absorbed by the cysts previously were released. Twenty-four hours after exposure the release rates increased to 75-85%, and the release of the drugs from the cyst wall was somewhat faster than that from cyst fluid.

Comparative study on gastric absorption of albendazole and mebendazole in rats

1. A study was carried out to determine the kinetics of the gastric absorption of two wide spectrum benzimidazole anthelmintics, albendazole and mebendazole. 2. The method used was gastric recirculation of solutions containing the drugs in concentrations ranging from 0.5 to 100 mM. 3. The results obtained showed that absorption corresponds to first order kinetics, with diffusion constants of 0.0087 min-1 for albendazole and 0.0077 min-1 for mebendazole. 4. Blood levels of the drugs for the whole range of concentrations were always higher in the case of albendazole.

The chemotherapy of onchocerciasis. XIV. Studies with mebendazole citrate

Twenty patients from an area of vector control in the savannah region of northern Ghana with moderate to heavy infection with Onchocerca volvulus were randomised to receive two priming doses of levamisole 150 mg on two occasions followed either by mebendazole-citrate (500 mg) given daily or twice daily for 14 days. The two dose levels produced a similar effect on skin microfilariae (80-88% reduction) with a very mild systemic clinical reaction: low levels were maintained over 42 weeks. Both regimes were embryotoxic for O. volvulus; an effect which was transient in the single dose group but persisted for more than three months in the twice daily dose group. Mebendazole-citrate appeared to be absorbed more predictably than has been observed previously for mebendazole. The degree of systemic exposure as determined by measurement of AUC (0-24 h) was 2.5 times greater for the twice daily dose as compared to the single dose and this fact was reflected in the efficacy of the two dose regimes against the adult female worms at three months.

[Experimental chemotherapy of alveolar hydatid disease. 12. The efficacy of drug forms of mebendazole and nocodazole with high bioavailability]

New formulations have been designed to increase the efficacy and bioavailability of the oral drugs mebendazole and nocodazole and were tested in CBA mice. A considerable increase in efficacy was established for a solid disperse formulation of certain composition with a relatively lower toxicity than in aqueous suspensions of the drugs.

[Clinical trial of the possibility of increasing the bioavailability of mebendazole using sunflower oil in echinococcosis]

Increasing mebendazole bioavailability is one of the most important problems to be solved in echinococcosis chemotherapy. The method of mebendazole administration with sunflower oil, elaborated by the authors, serves to this purpose: drug concentration exceeding the minimal effective one was attained in 86% patients treated with mebendazole and sunflower oil and only in 40% patients treated with the drug alone.