Prodrugs febantel

Febantel is a prodrug anthelminthic metabolized in vivo to fenbendazole and thereafter to oxfendazole. It is administered to cattle, sheep, and swine for treatment and control of gastrointestinal nematodes at dosages of 5-7.5 mg/kg bw. Fenbendazole, although not teratogenic per se, gives rise to the teratogenic oxfendazole. 

Several related analogues of the benzimidazoles are also anthelmintics including the imidazopyridine (5), tioxidazole (6), and the prodrugs, thiophanate (7) and febantel (8). However, although the benzimidazoles and related anthelmintics have proved a rich source of drugs, there is now evidence of widespread resistance to them, particularly in sheep parasites. Moreover, some benzimidazole carbamates are suspect in respect of teratogenicity and mutagenicity. 

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 Tetramisole has been superseded by levamisole.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. 

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