Anthelminthics

Nuts have many uses, both industrial and domestic. For instance, the ivory nut, or tagua, is a source material for the manufacture of buttons and turnery articles. The kola nut supplies ingredients for popular cola beverages in the United States (see Carbonated beverages). StTychnos nux-vomica provides the important medicine and poison, strychnine. The areca or betel nut is chewed by the Indian and Malayan people as a narcotic a slice of the nut is placed in a leaf of the pepper plant Piper betle) together with a pinch of lime the mixture is an acrid, astringent narcotic that dyes the mouth red, blackens and destroys the teeth. The areca nut contains, among other alkaloids, arecoline, an active anthelminthic widely used in veterinary practice for the treatment of tapeworm infections. 

Having discussed amides that carry an aromatic group on either the nitrogen or the carboxy side of the amide bond (i.e., anilides or benzamides, respectively), we continue our presentation with compounds in which the amide bond links two aromatic systems. The simplest structure in this class is A-phenylbenzamide (4.154). The influence of the nature and position of substitution on the rate of hydrolysis of a series of A-phenylbenzamides was investigated in mouse and sheep liver homogenates, with the goal of elucidating the metabolism of the anthelminthic niclosamide (4.158) [102],... 

Abiotic model systems, 258t of bioactivity, 258-60 Absorption, distribution coefficients, 228 Absorption rate, equation, 228 Acephate, structure, 97 N-Acetylation, biogenic amines, 114 Actinomycete, anthelminthic activity, 5... 

Interferons—a family of glycoproteins processed by macrophages—also are widely used as immunostimulants (a -interferons), made in macrophages and fibroblasts (j3-interferons), made in lymphocytes (7-interferons), which are named for their ability to react with viral RNA and affect protein synthesis. Commercially accessible a-, fi-, and y-interferons are currently used in medicine. Practically the only purely synthetic immunos-timulant drug that is used is levamisole, which was initially proposed as an anthelminthic agent, and it is currently widely used as such. 

Horton J Albendazole A broad spectrum anthelminthic for treatment of individuals and populations. Curr Opin Infect Dis 2002 15 599. [PMID 12821837]... 

Anthelminthic is derived from the Greek words anti and helminth. Anthehninthics are therefore drugs that act against internal parasites of animals collectively called helminths. 

Anthelminthics are used most frequently in spring and would not be given immediately prior to slaughter, thus reducing the likelihood of residues in edible animal products. Animals less than 1 year old are more susceptible to parasitic infections than adults and are treated more frequently than adults. Residues are most likely to be found in milk when the withdrawal periods have not been strictly observed or in the liver since this organ is the target tissue for the metabolism of anthelminthics. 

The benzimidazole group of anthelminthics is derived from the simple benzimidazole nucleus and includes the thiabendazole analogues and the benzimidazole carbamates. Substitution of side chains and radicals on the benzimidazole nucleus gives rise to the individual members of this group (Fig. 4.1). 

A number of benzimidazoles exist as prodrugs their anthelminthic activity is due to the fact that they are metabolized in the animal body to the biologically active benzimidazole carbamate nucleus. Due to their relatively slower excretion rates, the newer insoluble benzimidazoles have fairly long withdrawal periods for edible tissues and milk in contrast to the less effective and more rapidly excreted thiabendazole analogues. Strict compliance with withdrawal periods is always necessary because of the potentially toxic and teratogenic effects of some of the benzimidazoles and their metabolites. 

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. 

Parbendazole is an old anthelminthic that has been widely used against gastrointestinal nematodes and lungworms in cattle, sheep, and swine at dosages in the range 15-50 mg/kg bw. It is the drug in which the teratogenic effects of benzimidazoles were first identified. 

Oxibendazole is a broad-spectrum anthelminthic used for treatment of intestinal nematodes in various animal species including pigs, cattle, sheep, and horses. It is given as a single oral dose of 5-15 mg/kg bw or incorporated in feed at a dosage of 40 mg/kg feed/day for 10 days. Oxibendazole and its metabolites are not teratogenic. 

Flubendazole is used against gastrointestinal nematodes and lungworms in swine and poultry at dosages of 5 mg/kg bw or 30 ppm in the feed. This anthelminthic is poorly absorbed from the gut and, therefore, exhibits low toxicity. 

Triclabendazole is a very potent anthelminthic used against all stages of liver flukes in sheep, goats, and cattle at dosages of 10-12 mg/kg bw. This drug does not exhibit nematocidal activity and is not teratogenic. 

The racemic DL-tetramisole and its levo-isomer, levamisole, constitute the best-known members within this group of drugs (Fig. 4.2). Since the anthelminthic activity of tetramisole, which was first marketed in 1966, resides almost entirely in its levo-isomer, levamisole rather than the parent tetramisole is the drug currently used in most countries. 

Haloxon is probably the safest of the organophosphate anthelminthics (37). It is approved by the Food and Drug Administration (FDA) for use in sheep, cattle, and goats at a dosage of 30-50 mg/kg bw. It is not intended for use in swine and poultry, although certain parasites can be very effectively controlled by the drug in these hosts. It is usually administered orally in the form of a paste, bolus, drench, or liquid suspension, and as a feed premix for poultry. 

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