The disposition of 14C-levamisole in the lactating cow

Anthelmintics in the environment: Their occurrence, fate, and toxicity to non-target organisms

Anthelmintics are drugs used for the treatment and prevention of diseases caused by parasitic worms (helminths). While the importance of anthelmintics in human as well as in veterinary medicine is evident, they represent emerging contaminants of the environment. Human anthelmintics are mainly used in tropical and sub-tropical regions, while veterinary anthelmintics have become frequently-occurring environmental pollutants worldwide due to intensive agri- and aquaculture production. In the environment, anthelmintics are distributed in water and soil in relation to their structure and physicochemical properties. Consequently, they enter various organisms directly (e.g. plants, soil invertebrates, water animals) or indirectly through food-chain. Several anthelmintics elicit toxic effects in non-target species. Although new information has been made available, anthelmintics in ecosystems should be more thoroughly investigated to obtain complex knowledge on their impact in various environments. This review summarizes available information about the occurrence, behavior, and toxic effect of anthelmintics in environment. Several reasons why anthelmintics are dangerous contaminants are highlighted along with options to reduce contamination. Negative effects are also outlined.

Investigation of the persistence of levamisole and oxyclozanide in milk and fate in cheese

In this study, dairy cows (n = six) were treated with an oral combination product containing levamisole (5 mg/kg body weight, (bw)) and oxyclozanide (10 mg/kg bw). Animals were milked twice daily up to day 16 post-treatment. Milk samples were subsequently analyzed by ultraperformance liquid chromatography coupled to tandem mass spectrometry (UPLC-MS/MS). The highest levels of levamisole (<600 μg/kg) and oxyclozanide (<25 μg/kg) were determined at first and third milking, respectively. Residues of levamisole and oxyclozanide were typically below reporting limits of 0.83 and 1 μg/kg respectively at the 11th and 13th milking, respectively. Soft (3 days ripening), hard (35 days ripening) and whey cheeses were produced from the milk samples collected from the first two milkings. Levamisole residues were found to concentrate in all cheese types. There was a 3-fold concentration effect for levamisole in mature cheese. Oxyclozanide residues were found to occur at lower levels in soft and hard cheese than milk with a 10-fold concentration in whey cheese compared to milk. The results of this study demonstrate that levamisole and oxyclozanide residues are rapidly excreted in dairy cows and milk is compliant after a few days. Oxyclozanide and levamisole residues were shown to be stable during the fermentation process and the whey heat treatment to persist in cheese.

Inhibition by levamisole of the organic cation transporter rOCT1 in cultured rat hepatocytes

Levamisole is known to be subject to hepatic removal and metabolism and to biliary excretion. The aim of our work was to study the mechanism involved in the removal of this compound by the liver. For this purpose, we studied the influence of levamisole on the uptake and efflux of the model organic cation 1-methyl-4-phenylpyridinium (MPP(+)) by primary cultured rat hepatocytes. Levamisole (500 microm) was found to produce a strong inhibition (to 31+/-2% of control) of [(3)H]MPP(+)uptake. Moreover, efflux of [(3)H]MPP(+)was also potently reduced by levamisole (500 microm). Our results show that levamisole interferes with an hepatic organic cation transporter which accepts MPP(+)as a substrate. This mechanism most probably corresponds to rOCT1, and it might be responsible for the hepatic removal of levamisole from the blood circulation.

A highly sensitive gas chromatographic determination of levamisole in milk

An efficient extraction and sensitive gas chromatographic method is described for the determination of the anthelminthic drug levamisole in milk. Levamisole was extracted from alkaline milk with ethyl acetate. Clean-up of the extract was by a series of liquid-liquid extraction steps. Levamisole residues in the extract were determined by gas chromatography with a nitrogen-phosphorus detector. This method was satisfactory for determining levamisole residues in milk as low as 0.5 ng/g. Mean recoveries of 0.5-10.0 ng/g fortified milk samples ranged from 84.5 to 95.2%. Five replicate analyses performed on a milk containing incurred levamisole residues yielded a mean of 3.34 ng/g levamisole with a CV of 3.0%.