Rapid drug detection in whole blood droplets using a desorption electrospray ionization static profiling approach - a proof-of-concept

RATIONALE

The introduction of desorption electrospray ionization (DESI) - and ambient desorption/ionization (ADI) ion sources in general - in the 2000s has opened new possibilities for mass spectrometric (MS) analyses of biological sample surfaces. DESI allows for a rapid screening of solid samples because no sample preparation is needed and the analysis is performed at atmospheric pressure. In the present study, we used DESI as an ion source for the rapid detection of a small molecule in blood droplets deposited on glass slides.

METHODS

Blood was spiked with different concentrations of a model drug, mebendazole. One microliter blood droplets of each preparation were deposited on the surface of a glass slide and analyzed by DESI, either in imaging or profiling mode.

RESULTS

The results suggested that DESI imaging mode was not appropriate for the detection of mebendazole in blood droplets as an initial solvation time was necessary before the obtention of signal. A profiling approach consisting of analyzing a single position of the blood droplet was used for further analysis and allowed mebendazole to be detected in the fg range and to monitor the volume of sample analyzed.

CONCLUSIONS

The study suggests that profiling mode at a single position is adequate for DESI analyses in whole blood droplets. This proof-of-concept study illustrates the potential of DESI profiling as a possible alternative to liquid chromatography/MS analyses of whole blood, when analyses are needed within a restricted time. Rapid detection methods in blood at atmospheric pressure may find interesting applications in the fields of toxicology and pharmacology.

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.

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.

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.

Immunosurveillance of alveolar echinococcosis by specific humoral and cellular immune tests: long-term analysis of the Swiss chemotherapy trial (1976-2001)

BACKGROUND/AIMS

Long-term chemotherapy with benzimidazoles is beneficial in non-resectable alveolar echinococcosis (AE). Criteria to track early therapeutic efficacy are lacking and the clinical impact of immunosurveillance is unsettled. We aimed to analyze this issue particularly for assessing the putative parasitocidal efficacy of chemotherapy.

METHODS

The present study is part of our prospective Swiss trial outlined previously and comprises 57 patients with a median follow-up of 18.5 (3-30) years and with repeated tests of humoral and cell-mediated immunity. The series was subdivided into group A (n=23; curative surgery) and group B (n=34: non-resectable AE).

RESULTS

Long-term survival was 87% (group A) and 76% (group B). The profiles of specific antibodies against EmII/3-10 antigen normalized within 3 years in most group A-patients, but remained above the cut-off value in 40% of group B-patients. This lack of normalization was associated with lower bioavailability of mebendazole. AE-recurrence after 'radical' surgery (up to 13 years) was associated with high anti-EmII/3-10 concentrations in 7 of 8 cases. Following abrogation of longterm chemotherapy in group B, no AE-recurrence occurred in 9/18 patients, suggestive of parasitocidal efficacy and documented by a normal EmII/3-10 profile.

CONCLUSIONS

The EmII/3-10 profile is of value in monitoring AE after surgery and/or chemotherapy.

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.

Polarographic determination of flubendazole in spiked human urine and plasma

The voltammetric behavior of flubendazole was studied using direct current (DCt), differential pulse (DPP) and alternating current (ACt) polarography. The drug manifests a cathodic wave in 20% v/v formic acid solution. The wave was characterized as being irreversible, diffusion-controlled with limited adsorption properties. The diffusion current-concentration relationship was found to be rectilinear over the range 3.2-14.4 microg/ml and 0.1 to 12.8 microg/ml, using DCt and DPP modes, respectively, with minimum detectability of 0.161 microg/ml (5.14 x 10(-7) M) and 0.0.057 microg/ml (1.82 x 10(-8) M) using DCt and DPP modes, respectively. Furthermore, the proposed method was applied to the in-vitro determination of flubendazole in spiked human urine and plasma adopting the DPP technique. The percentage recoveries were 100.20+/-0.62 and 97.42+/-0.95, respectively.

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.

Determination of antifilarial compound UMF-078 and its metabolites in plasma by high-performance liquid chromatography

UMF-078, methyl (+/-)-[5-(alpha-amino-4-fluorobenzyl)benzimidazol-2-yl]carba mate, is a new antifilarial compound being developed by the World Health Organization. In the present study, a HPLC method for the simultaneous estimation of UMF-078 and its metabolites (flubendazole, decarbamoylated flubendazole, UMF060 and decarbamoylated UMF-060) in plasma was developed, validated and applied to pharmacokinetic studies. Linearity was observed between 20 and 1000 ng/ml for decarbamoylated UMF-060 and between 10 and 500 ng/ml for other analytes. Recoveries were consistent over the concentration ranges studied for all the analytes. Variations in intra- and inter-batch accuracy and precision were within acceptable limits of +/-20% at the lowest limit of quantitation, whereas at higher concentrations it was +/-15%. The analytes showed stability up to two freeze-thaw cycles in plasma. No degradation was observed for any of the analytes even after 72 h of storing the dry plasma extracts at -30 degrees C. The assay method was employed to study the pharmacokinetics of hydrochloride salt of UMF-078 in rats. The parent compound and its metabolites viz: decarbamoylated UMF-060, UMF-060 and flubendazole were quantitated in serum and the compounds could be monitored up to 168 h post-dose.

Clastogenic and aneugenic effects of three benzimidazole derivatives in the in vitro micronucleus test using human lymphocytes

Three benzimidazole compounds thiabendazole (TBZ), carbendazim (MBC) and mebendazole (MEB) were analysed with the in vitro cytochalasin-B micronucleus test on human lymphocytes. TBZ was tested in isolated lymphocyte cultures and MBC and MEB were tested in both isolated lymphocyte and whole blood cultures. TBZ was tested up to 300 microM with and without S9-mix. Although signs of toxicity, without S9, were observed by a decrease in the division index at 300 microM, an increase in the frequency of micronucleated binucleates was not found with or without S9. MBC and MEB induced a statistically significant concentration-dependent increase in the micronucleus frequency. The effective concentration range for MEB (0.3-1.5 microM) was ten times lower than for MBC (5-25 microM). By means of fluorescence in situ hybridization with a 30 nucleotide oligomer of the alpha centromeric regions, common for all chromosomes, on the induced micronuclei MBC and MEB were found to induce a significant increase of centromere positive micronuclei in a dose-dependent manner. MBC and MEB are poorly soluble in water and therefore have a low bioavailability in vivo. However, increased micronucleus frequencies were found in this in vitro micronucleus study at doses comparable to in vivo plasma levels in mice and should, therefore, not be neglected in the risk evaluation of those compounds.

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.

Plasma levels of mebendazole in children with hydatid disease

The plasma levels of mebendazole in children with hydatid cyst disease were measured with high pressure liquid chromatography. In 24 children who received mebendazole orally in a dose of 50 mg/kg, the mean (SD) level 4 hours later was 25.76(9.81) ng/ml (87.6(33) nanomole/l). This result was similar to those in most adult series. During more prolonged treatment, the plasma level 4 hours after the dose of the drug rose significantly with respect to the initial level (p < 0.05).

Application of a high-performance liquid chromatography coulometric method for the estimation of mebendazole and its metabolites in human sera

A novel, sensitive high-performance liquid chromatographic method, making use of coulometric detection, for the estimation of mebendazole and its metabolites in the sera of eight hydatidosis patients was devised. Recovery rates, precision, accuracy and sensitivity for each compound are reported and compared with those of the previously published methods.

Hepatotoxicity of mebendazole. Relationship with serum concentrations of the drug

We report the case of a 47-year-old female patient, suffering from multiple hydatid cysts of the liver, in whom hepatitis developed after mebendazole treatment. Clinical manifestations of hypersensitivity were absent. A correlation was found between serum mebendazole concentrations and the degree of cytolysis; this is compatible with a direct hepatotoxic effect of mebendazole.

Cimetidine increases serum mebendazole concentrations. Implications for treatment of hepatic hydatid cysts

In eight patients (five with peptic ulcer disease and three with hydatid cysts), the [14C]-aminopyrine breath test (ABT) and maximum serum concentration of mebendazole following a dose of 1.5 g of mebendazole three times daily were determined before and after treatment with cimetidine (400 mg three times daily for 30 days). Serum mebendazole concentrations were measured in blood samples taken 2 h after each drug intake. Cimetidine lowered the 14CO2 specific activity (SA) at 1 h (P less than 0.01) and increased the maximum serum concentration of mebendazole (P less than 0.01). A significant correlation was found between SA at 1 h and the highest concentration of mebendazole before (r = -0.71, P less than 0.05) and after (r = -0.82, P less than 0.05) cimetidine ingestion. Combined administration of cimetidine and mebendazole resulted in the complete resolution of previously unresponsive hydatid cysts.

A correlation between serum mebendazole concentrations and the aminopyrine breath test. Implications in the treatment of hydatid disease

In 25 patients an [14C]-aminopyrine breath test (ABT) was performed immediately before the oral administration of 1.5-2 g of mebendazole three times daily. The concentration of mebendazole in serum was measured 2 h after each drug intake. A significant correlation was found between the results of ABT and the serum drug concentrations obtained after the second and third intake, as well as the highest concentration value. The ABT was repeated in six patients during a continuous treatment with mebendazole. In all of them this test indicated an increase in 14CO2 production with continued treatment. The results support the view that mebendazole is metabolized by the liver monooxygenase activity and behaves as an enzyme inducer.

Treatment of hydatid disease with high oral doses of mebendazole. Long-term follow-up of plasma mebendazole levels and drug interactions

Plasma mebendazole levels were analysed retrospectively in patients treated for inoperable infections with Echinococcus multilocularis or granulosus. In 10 patients receiving mebendazole at 4 dose levels there was no relation between dose and plasma concentration. In 17 patients followed on the same dose for more than 18 months, the plasma levels varied with individual coefficients of variation ranging from 27 to 72%. The data reveal the limitations of single measurements of plasma mebendazole and emphasize the need for repeated monitoring. Coadministration of phenytoin and carbamazepine seemed to lower plasma levels, presumably as a result of enzyme induction. It was not possible appreciably to raise the mebendazole concentrations by inhibition of drug metabolizing enzymes with cimetidine.

Serum concentrations of mebendazole in patients with hydatid disease

Mebendazole was administered to 22 patients, 17 of whom had developing or cured hydatid cysts, and to 5 volunteers. Then, at regular intervals, it was titrated by radioimmunoassay in the serum for 24 hours. Serum levels after the intake of 1 gram were perceptible on an empty stomach; they were higher when the drug was taken with a rich meal, but the difference was not statistically significant. The administration of increasing therapeutic doses (3, 4.5, 6 and 12 g a day) led to a concomitant increase of the average serum levels of mebendazole; concentrations varied between a minimum of 7.6 ng/ml and a maximum of 483 ng/ml. The difference between the various average concentrations was only significant after 8 hours when increasing from 3 to 6 g a day. The absence of a significant difference for the other average concentrations was due to the large interindividual variations. However, analysis of the individual results shows an increase of the serum concentrations parallel with that of the dose in 10 out of 12 patients. The effect of the dose seems to vary with the patient and the dose received. Blood samples taken 2 hours after each of the 3 daily drug intakes could give more information as to the serum concentrations susceptible to influence the parasite. The drug's half life, lying between 3.3 and 11.5 hours in 5 patients, is longer in case of major hepatic dysfunction, due to established hepatopathy. During the monitoring of 7 patients, the average serum levels were comparable with or higher than the initial concentration.

Effect of plasma mebendazole concentrations in the treatment of human echinococcosis

High oral doses of mebendazole were given for a mean period of 23 months to 22 patients with inoperable alveolar or cystic echinococcosis (Echinococcus multilocularis n = 18, E. granulosus n = 4). Clinical, morphological, biochemical and serological findings and plasma mebendazole levels were monitored. Clinical and biochemical improvement or stabilization was observed in 17 patients but the parasitic lesions did not decrease in size in most instances. One patient died shortly after onset of therapy with hemorrhage of esophageal varices. Three patients with alveolar and one with cystic echinococcosis had evidence of progressive disease such as increase of cholestasis, destruction of lumbar vertebrae and growth of an intraperitoneal cyst. The plasma mebendazole levels (4 hr after the morning dose) of the latter 4 patients were 0.09 +/- SD 0.02 mumol/l, while in those with clinical stabilization or improvement it was 0.30 +/- SD 0.14 mumol/l (P less than 0.001). These preliminary data indicate 1) a good clinical response to chemotherapy in most patients despite unchanged size of the parasitic lesions, and 2) a direct correlation of clinical response with plasma mebendazole levels.

High oral doses of mebendazole interfere with growth of larval Echinococcus multilocularis lesions

The natural development of the larval stage of Echinococcus multilocularis in man has been studied in 7 patients after presumed radical operation 2 8/12-11 2/12 years prior to detection of a relapse. The volumes of the recurring lesions were assessed by CT-scanning, and assuming linear growth a median increase of 14.8 ml/year (range 3.8-220 ml/year) was calculated. In 6 patients treated for a median duration of 4 5/12 years with high oral doses of mebendazole a median growth rate of -3.0 ml/year (range-470- + 10.2 ml/year) was found, which differed significantly from the natural growth rate (P less than 0.01). Although the patients improved clinically, there was evidence of persistent infection. These data are the first controlled evidence that high oral doses of mebendazole may be parasitostatic in alveolar echinococcosis in man. Although not curative, this pharmacological effect appears to be clinically beneficial.

Liquid chromatography with electrochemical detection for monitoring mebendazole and hydroxymebendazole in echinococcosis patients

A sensitive method is described for the simultaneous determination of mebendazole and hydroxymebendazole using flubendazole as an internal standard. The analytes were isolated with a single chloroform extraction from 1.0 ml of alkalinized plasma or cyst liquid samples. Separation and quantitation were performed with high-performance liquid chromatography with electrochemical detection. The limit of detection for mebendazole and hydroxymebendazole was approximately 5 and 2.5 ng/ml, respectively. The accuracy of the method was confirmed for mebendazole by a good correlation with an existing radioimmunoassay method. The method was applied for monitoring mebendazole therapy in echinococcosis patients. The results presented support the necessity of such monitoring, as most of the observed peak plasma concentrations did not reach the level regarded as minimal for therapeutic effect.

4-Amino-3-(3'-methoxycarbonyl-2'-thioureido)benzophenone, a prodrug of mebendazole

The compound 4-amino-3-(3'-methoxycarbonyl-2'-thioureido) benzophenone has shown promise as a prodrug of the anthelmintic mebendazole. The compound is stable in acid and neutral media and is rapidly hydrolysed in base. An HPLC assay procedure for mebendazole, the prodrug and their known or expected metabolites and degradation products in aqueous media and rat blood has been developed. The prodrug administrated orally to rats is rapidly converted to mebendazole. The area under the blood level versus time curve of mebendazole, in rats dosed with the prodrug, is more than twice that obtained after dosing rats with an equimolar amount of mebendazole. Only the prodrug, mebendazole and known metabolites of mebendazole are detected in rats dosed with the prodrug.

The metabolic and pharmacokinetic disposition of mebendazole in the rat

The metabolism and pharmacokinetics of mebendazole was studied in rats using [2'-3H]-mebendazole (biologically stable; specific activity 383.9 (mCi/mMol) and [2-14C]-mebendazole (specific activity 2.57 mCi/mMol). Analyses were performed by high pressure liquid chromatography and liquid scintillation spectrometry. About 85% of an intravenous dose was eliminated with the bile and the remainder with the urine. The majority of the dose was recovered as conjugated metabolites. The major metabolite (methyl-5(6)-(alpha-hydroxybenzyl)-2-benzimidazole carbamate) accounted for about 77% of the total recovered and 99% of it was conjugated. Anaerobic metabolism studies conducted in vitro with intestinal microorganisms obtained from rats indicated that metabolism of mebendazole did not occur in the gut, but that the intestinal microflora was able to hydrolyse conjugated metabolites which were eliminated with the bile. Mebendazole was found to have a biphasic elimination profile after intravenous administration. Its terminal plasma elimination half-life was 3.2 hours and its re-distribution half-life was 0.4 hour. After oral administration, as a solution in aqueous dimethyl sulphoxide, a bioavailability of 53% was obtained.

Mebendazole treatment of Echinococcus granulosus infection. Report of a case

A patient with an Echinococcus granulosus cyst of the liver was treated with mebendazole for 94 days before operation. The serum levels of mebendazole varied from 39.4-274 ng/ml. After operation, cyst materials were inoculated into mice which developed hydatid cysts 10 months later. Intestinal absorption of mebendazole is poor and variable, and determination of serum concentrations is necessary during treatment. No apparently successful cases of drug treatment of E. granulosus infection have been verified by animal inoculation of cyst material; therefore, surgery must still be considered the treatment of choice. It is recommended that mebendazole be given prophylactically to prevent spread of the disease at operation.

Treatment of trichinosis with mebendazole

Prolonged oral high-dose mebendazole therapy provided an effective anthelmintic regimen for trichinosis unresponsive to steroid therapy in one patient. Side effects were limited to a Herxheimer-like reaction. Serum mebendazole levels documented gastrointestinal absorption. Repeat muscle biopsies and fluorescein angiography substantiated objective improvement.

Severe, reversible neutropenia during high-dose mebendazole therapy for echinococcosis

Two patients receiving oral high-dose mebendazole therapy for echinococcosis were found to have severe, reversible neutropenia, apparently due to marrow suppression; platelets and RBCs were also reversibly suppressed in one. High blood levels of mebendazole (239 ng/mL) in one patient may have resulted in the neutropenia and several toxic side effects, as well as a striking shrinkage of the patient's pulmonary and liver cysts. Neutropenia with high-dose mebendazole therapy may occur in up to 5% of patients and may be much more common than previously recognized. The WBC count should be monitored frequently during the first several weeks of therapy. Further experience will be needed to determine whether neutropenia is related to mebendazole levels.

Chemotherapy of larval echinococcosis with mebendazole: microsomal liver function and cholestasis as determinants of plasma drug level

High oral doses of mebendazole have been only partly effective in the treatment of patients with alveolar or cystic echinococcosis, possibly due to an inadequate plasma concentration of the drug in some patients. In order to improve therapeutic results the influence of liver function on the plasma levels of mebendazole was investigated during long term therapy. Plasma mebendazole concentrations measured before the morning dose (trough values) showed a highly significant, negative correlation both with the aminopyrine breath test (ABT; rs = -0.78, n = 14, p less than 0.001) and the second exponential component of bromsulphthalein elimination (BSP- k2; rs = -0.74, n = 12, p less than 0.01). These relationships also applied over longer than a single day, since trough and peak mebendazole levels observed over an interval of 6 months before and after testing liver function were equally well correlated with ABT and BSP-k2. The daily dosage and other liver function tests seemed to be of minor importance in determining the plasma levels. It was concluded that the microsomal function of the liver and/or cholestasis might be important determinants of plasma mebendazole levels. The results of the study imply that higher and more effective mebendazole concentrations might be achieved by inhibition of the drug metabolizing capacity of the liver rather than by increasing the dose of mebendazole.

Mebendazole concentrations in sheep plasma

Formulated mebendazole was administered to sheep by intraruminal injection at dose rates of 12.5, 25, 50 or 100 mg/kg bodyweight. The concentrations of mebendazole and two major metabolites were measured by high-performance liquid chromatography in plasma taken at intervals up to 48 hours after treatment. At 12.5 mg/kg the peak plasma concentration was 0.22 +/- 0.03 microM mebendazole, rising to 0.76 +/- 0.04 microM at 100 mg/kg. Peak plasma concentrations occurred between nine and 24 hours for all dose rates and declined rapidly. Two major metabolites were detected; their concentrations exceeded that of mebendazole at all dose rates.

Treatment of human echinococcosis with mebendazole. Preliminary observations in 28 patients

Preliminary results of a long-term, prospective therapeutic trial with mebendazole in 28 patients mainly with inoperable echinococcosis are reported. The course of disease was monitored closely and plasma mebendazole levels were checked regularly. A major problem is the lack of reliable methods for defining and measuring early success or failure of therapy. Most of the patients improved clinically. No marked change of parasitic lesions was observed except in one patient with constantly low plasma mebendazole levels who deteriorated. No serious side effects occurred. The preliminary results are encouraging and suggest that mebendazole has a "parasitostatic" effect on larval growth.

Clinical pharmacokinetics of high dose mebendazole in patients treated for cystic hydatid disease

The plasma concentrations of mebendazole and its metabolites have been monitored in twelve patients after receiving a 10 mg/kg dose for cystic hydatid disease. The mebendazole plasma concentration-time profiles differed considerably between patients; elimination half-lives ranged from 2.8-9.0 h, time to peak plasma concentration after dosing ranged from 1.5-7.25 h and peak plasma concentrations ranged from 17.5 to 500 ng/ml. The mean peak plasma concentration of mebendazole after an initial dose (69.5 ng/ml) was lower than found in patients during chronic therapy (137.4 ng/ml). The plasma AUCTS for the major metabolites of mebendazole (methyl 5-(alpha-hydroxybenzyl)-2-benzimidazole carbamate and 2-amino-5 benzoylbenzimidazole) were about five times the plasma AUCT found for mebendazole in patients on chronic therapy. It is suggested that the slower clearance of these polar metabolites relative to mebendazole results from enterohepatic recycling. Since mebendazole is also highly plasma protein bound, caution should be observed in administering mebendazole to patients with liver disease. Concentrations of mebendazole found in the tissue and cyst material collected from two patients during surgery ranged from 59.5 to 206.6 ng/g wet weight.

Chemotherapy of alveolar echinococcosis. Comparison of plasma mebendazole concentrations in animals and man

High oral doses of mebendazole have been only partly effective in the treatment of patients with alveolar or cystic echinococcosis. In order to improve therapeutic results the pharmacology of mebendazole has been investigated. Jirds experimentally infected with larval Echinococcus multilocularis were given food containing mebendazole 100 to 1000 ppm. Drug plasma concentrations above 0.25 mumol/l were associated with a reduction in parasite weight to 1 to 10% of that in untreated controls. In treated animals parasite weight was negatively correlated with the plasma mebendazole concentration and with the duration of therapy. In patients on long term therapy with similar doses of mebendazole (16 to 48 mg/kg per day), plasma concentrations were much lower than in jirds. Only 19% of fasting plasma concentrations exceeded 0.25 mumol/l. Plasma concentrations 4 h after the morning dose did not exceed this value in 48% of cases. The results can be explained by the irregular drug absorption and short plasma half life observed in 7 hospitalized patients. It is likely that better results would be obtained if doses of mebendazole were adjusted to produce peak plasma levels exceeding 0.25 mumol/l.

Two high-performance liquid chromatographic determinations for mebendazole and its metabolites in human plasma using a rapid Sep Pak C18 extraction

A rapid extraction procedure for mebendazole and its metabolites from plasma using Sep Pak C18 is described. This method eliminates the need for solvent extractions as such. Two reversed-phase high-performance liquid chromatographic determinations for these extracts, one isocratic elution and the other gradient elution, using an analytical wavelength of 254 nm are also presented. The gradient elution system provides superior resolution of these compounds and consequently has improved determination limits. For mebendazole the determination limits are 20 ng/ml (isocratic system) and 10 ng/ml (gradient system).

Plasma concentrations of mebendazole during treatment of echinococcosis: preliminary results

High oral doses of mebendazole are used experimentally for the treatment of human alveolar and cystic echinococcosis. In order to assess bioavailability of this drug 1.5 g doses were given to 3 volunteers. Measurable plasma concentrations of 17 to 134 nmol/l were found only if mebendazole was given together with a fatty meal. In a patient with cholestasis plasma concentrations were higher than in the 3 normal subjects. In patients on long term treatment the increase in plasma concentration after administration of a 1 g dose varied between 0 and 500 nmol/l. It is concluded that systemic availability of mebendazole is enhanced by concomitant food intake. In view of the large intra- and interindividual variation in plasma concentration, monitoring plasma levels during long term therapy appears advisable.

High-performance liquid chromatographic assay for the anthelmintic agent mebendazole in human plasma

A rapid and specific high-performance liquid chromatographic (HPLC) assay for quantitative plasma mebendazole determination is described. After a simple extraction, the compound was analyzed by HPLC using a reversed-phase column and a UV detector (313 nm). Quantitation was accomplished using an internal standard; peak area ratios were determined with an integrating computer. The average mebendazole recovery over a concentration range of 0.01-0.20 microgram/ml was 75.9 +/- 3.8% SD, and the maximum assay sensitivity was approximately 10 ng/ml.