The maternal-foetal distribution of thiabendazole administered in two different vehicles to pregnant mice.

We have compared the effects of two vehicles on the maternal-foetal distribution of 14C-thiabendazole ([14C]TBZ) given orally to Jcl: ICR mice on day 9 or 16 of gestation. TBZ, either suspended in olive oil (TBZ-O) or in a 0.5% aqueous solution of gum arabic (TBZ-G), was given orally on day 9 of gestation at a dose of 1 g/kg body weight (1 microCi/mouse). The mice were killed 0.5, 1, 3, 6, 12, 24 or 72 hr later. In mice treated with TBZ-O maximum levels of radioactivity in plasma and conceptuses were observed at 0.5 hr, whereas in those treated with TBZ-G maximum 14C levels were observed at 6 hr. The uptake of radioactivity from TBZ-O into the plasma and conceptuses was significantly higher than that from TBZ-G. Only trace levels of radioactivity were detected at 72 hr in both treatment groups. The placental transfer of [14C]TBZ was examined in mice treated with doses of 1 g/kg body weight (1 microCi/mouse) given as TBZ-O or TBZ-G on day 16 of gestation. The radioactivity in foetuses, placentas and maternal plasma was higher in mice treated with TBZ-O than those given TBZ-G. The placental transfer of [14C]TBZ was also examined by whole-body autoradiography in mice treated on day 16 of gestation.

HPLC determination and pharmacokinetics of thiabendazole and its major metabolite 5-OH thiabendazole in equine plasma.

Separate high performance liquid chromatographic methods were developed for thiabendazole (TBZ) and 5-hydroxy thiabendazole (5-OH-TBZ) determination in horse plasma using 1-methyl-2-phenyl benzimidazole (MPBZ) as an internal standard. In both methods TBZ and 5-OH-TBZ were extracted from plasma using organic solvents, injected on to a C-18 column, and eluents monitored by a fluorescence detector. However, mobile phase composition, extraction solvent as well as detector wavelength differed in the two methods. The linear range for TBZ was 0.02 to 0.77 microgram ml-1 while that for 5-OH-TBZ was 0.96 to 8.0 micrograms ml-1. A commercially available TBZ oral suspension was administered to four thoroughbred horses in the following manner: days 1 and 2, 44 mg kg-1; days 4 and 5, 440 mg kg-1. Blood samples were collected during the 24 hours after administration and then analysed for TBZ and 5-OH-TBZ. Half-lives (t1/2), maximum plasma concentrations (Cmax), area under plasma concentration time curves (AUC O-alpha), and relative apparent bioavailability (F), were determined using pharmacokinetic equations. The pharmacokinetic parameters varied in the following manner: 1.16 to 13.63 hours (t1/2), 12 to 131 micrograms ml-1 X hours (AUC O-alpha), 3.33 to 8.90 micrograms ml-1 (Cmax), 1.38 to 0.12 (F) after 44 mg kg-1 and 440 mg kg-1 doses, respectively. The ratios of concentrations of TBZ to 5-OH-TBZ after oral administration of TBZ, were significantly lower for 44 mg kg-1 than 440 mg kg-1 doses.(ABSTRACT TRUNCATED AT 250 WORDS)

Solid-phase extraction and HPLC determination of levamisole hydrochloride in sheep plasma.

The anthelmintic, levamisole, was determined in sheep plasma by means of ion-pair solid-phase extraction (SPE) and reverse-phase liquid chromatography. The SPE columns were conditioned with 2 ml of methanol followed by 1 ml of octane sulphonic-acid buffer. After sample application, the columns were washed with 2 ml of the same buffer, followed by elution with 90/10 acetonitrile:buffer. A phenyl reverse-phase column (Spherisorb S5 Phenyl, 250 x 4.6 mm) was used with a mobile phase of acetonitrile: 0.005 M of octane sulphonic-acid sodium salt and 0.2% triethylamine in water, pH 3.5, 38/62. Extraction recoveries of 89-94% were achieved over the range from 100-3750 ng/ml. Accuracy and precision were better than 96% and 2.6%, respectively, over said range, with a limit of quantitation of 50 ng/ ml.

Determination of thiabendazole and 5-hydroxythiabendazole in human serum by fluorescence-detected high-performance liquid chromatography.

We have developed a rapid, sensitive and precise high-performance liquid chromatographic method using fluorescence detection for the simultaneous determination of thiabendazole and unconjugated 5-hydroxythiabendazole in serum. Sample pretreatment consists only of protein precipitation with acetonitrile containing the internal standard, 2-methylindole. Detection limits were found to be 0.1 microgram/ml serum for thiabendazole and 0.4 microgram/ml serum for 5-hydroxythiabendazole. Between-day analytical precision coefficients of variation for serum-based controls were 7% and 11% for thiabendazole levels of 1 and 5 micrograms/ml, respectively; and 43% and 8% for 5-hydroxythiabendazole levels of 6 and 60 micrograms/ml, respectively. We also devised a microenzymatic method for the conversion of the glucuronide and sulfate esters of 5-hydroxythiabendazole using beta-glucuronidase [EC 3.2.1.31] and sulfatase [EC 3.1.6.1]. Thus, quantitation of the separate metabolites was possible. We also utilized a special adaptation of the chromatographic procedure for the determination of the 5-hydroxythiabendazole metabolites in the sera of uremic patients, which can contain large amounts of interfering fluorescent substances. The method should be particularly useful for monitoring thiabendazole therapy in patients unable to eliminate the potentially toxic metabolites.

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.