Antiparasitic drugs anthelmintics

Since about 1952, the American public has been amply supplied with meat produced largely from animals that received feed containing antibiotics. These and other chemicals, including sulfonamides and antiparasitic drugs such as anthelmintics and coccidiostats added to feed, have saved labor, feed and space, thus revolutionizing animal agriculture. The record of safety of antibiotics in animal feed in the US has been excellent, including safety to producers and meat handlers as well as to consumers. 

Anthelmintics The major classes of anthelmintics, or antiparasitic drugs, are benzimidazoles and mac-rocyclic lactones (avermectins and milbemycins). USDA/FSIS have approved a method based on LC/ fluorescence detection for determination of the anthelmintics albendazole and ivermectin in tissues (albendazole extracted with ethyl acetate and cleanup... 

Some antiparasitic drugs, notably the macrocyclic lactones, have already been addressed in Chapter 6. This chapter will examine the toxic effects of other compounds that are widely used, or have been used, as antiparasitic drugs in animals. In Europe and elsewhere, the main anthelmintic drugs are the benzimidazoles and levamisole. The major benzimidazole drugs are thiabendazole, albendazole, fenbendazole, flubendazole, mebendazole, oxfendazole, oxiben-dazole, triclabendazole and albendazole sulphoxide (ricobendazole, albendazole oxide). Febantel and netobimin are two prodrugs that in vivo are converted to fenbendazole and albendazole, respectively. Levamisole is the levo ( ) isomer of (dextro isomers. Tetramisole has been superseded by levamisole. These and some other antiparasitic drugs are discussed in this chapter. 

Diethylcarbamazine is an anthelmintic drug that does not resemble other antiparasitic compounds although it has some relationship with piperazine derivatives and it has been useful in the management of filariasis due to Wuchereria bancrofti or Brugia malayi and Loa loa and of tropical eosinophilia. It is a lipoxygenase inhibitor and alters the surface structure of the parasite making it more susceptible to destruction by the host. It is well absorbed and widely distributed. It is eliminated with an half-life of 5-13 hours both by metabolism and excretion unchanged in the urine. 

The use of pyridine and quinoline derivatives in the growth of poultry and related animal industries is described in CHEC(1984) <1984CHEC(2)511>. In CHEC-II(1996) <1996CHEC-II(5)245>, discussion of veterinary products had subsections covering anthelmintics, antiparasitics, and antibacterials. It is pointed out in CHEC-II(1996) <1996CHEC-II(5)245> that drugs developed for human use often find a place in veterinary medicine. 

Whilst santonin was not primarily an Animal Health drug, it is a natural product with anthelmintic properties and, as we shall see later, today s antiparasitic market is dominated by a single class of natural products. Although since then, plant metabolites have played a commercial role, the major impact has been made by microbial natural products. 

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