[Background and Overview][1][2]
One of the bottlenecks in the treatment of coccidiosis today is that the drug resistance of coccidia is very serious, and the efficacy of the drugs is constantly declining. The extensive use of anthelmintic drugs has promoted the continuous emergence of drug-resistant strains. Large Western pharmaceutical companies have rarely developed new anthelmintic drugs due to drug residues and the concept of green farming. Many excellent anthelmintic drugs have been criticized for clinical use due to their water solubility problems and their inability to meet the requirements of modern large-scale production. elimination, all of which have resulted in fewer and fewer coccidiosis drugs available on the Chinese market, an increase in the number of coccidia outbreaks in the same batch of chickens, and an increase in the cost of coccidia control.
Fenbendazole is a new generation of chemically synthesized benzimidazole anthelmintic drugs. Its main structure is different from other anthelmintic drugs and there is no cross-resistance with other anthelmintic drugs. Laboratory studies have confirmed that fenbendazole has broad-spectrum anti-coccidial activity. It not only has high anthelmintic activity against adults and larvae of gastrointestinal nematodes, and has inhibitory and killing effects on various small intestinal coccidia. It has good effects on tail worms, fasciolia and tapeworms, and has a strong killing effect on insect eggs. It is an efficient, broad-spectrum and low-toxic anthelmintic. Fenbendazole is the latest and best international broad-spectrum, high-efficiency, low-toxicity, and low-residue antihelmintic drug for animals in recent years. It has a strong repellent effect on adults, larvae, eggs and fluke adults, larvae, and tapeworms of most nematodes in the gastrointestinal tract of horses, cattle, sheep, pigs, dogs, cats, poultry, deer, carnivorous raptors, etc. . Clinical application has proven that fenbendazole has a powerful killing effect on the following worms: ① Haemonchus elegans, Ostea nematode, Trichostrongylus elegans, Cooperia elegans, Leptocollar nematode, Yangostomia nematode, Xiabei nematode in cattle and sheep Adults and larvae of nematodes, esophageostomal nematodes, Trichocephalus nematodes, and Dictychocerciata nematodes; Monitz tapeworm extensifolia and Monitz tapeworm Bellinii. ②Parascaris of horses, adults and larvae of Apis tail nematode, Prevotella viviparous, Roundworm vulgaris, Strongyloides toothless, Small Roundworm nematode. ③Porcine roundworms, red strongyloides, esophageal stoma nematodes, and crown-tailed nematodes. ④ Canine hookworms, Trichocystis elegans, roundworms and their transitional larvae. ⑤Cat roundworms, hookworms, and tapeworms. ⑥Osteria nematode, Cooperia elegans, Leptocollar nematode, Trichocephala elegans, Trichostrongylus elegans, Lungworm and Monitz tapeworm. ⑦ Roundworms, saw nematodes, capillary nematodes and flukes of carnivorous raptors.
[Pharmacological effects and mechanism of action] [2]
Fenbendazole has a unique anti-helminthic effect. It is an inhibitor of eukaryotic cell tubulin and an inhibitor of energy metabolism. It can not only resist helminths, but also kill insect eggs. After oral administration, the drug is absorbed from the gastrointestinal tract and evenly distributed throughout the animal body. It has a long half-life, has the lowest dosage among similar drugs, and has a wide safety range.
[Toxicology][2]
Fenbendazole has low toxicity. According to acute test results in rats and mice, the lethal doses are 4015.76 mg and 6998.4 mg per kilogram of body weight respectively. The accumulation toxicity test coefficient K is less than 5 (no obvious accumulation); the maximum dose is both It is greater than 704.52 mg per kilogram of body weight and has no teratogenic, carcinogenic or mutagenic effects. The dose of 17 mg per kilogram of body weight of pregnant ewes did not cause abortion, there was no change in mental appetite, and only the sheep feces became soft. Sheep can tolerate 20 times the conventional treatment dose without symptoms of poisoning. The hemodynamic and tissue pharmacokinetic test results show that the drug is a low-residue veterinary drug. Fenbendazole should be taken orally to horses, cattle, sheep, pigs, and deer. The appropriate dosage is 5 mg per kilogram of body weight once, for dogs, 25-50 mg, for pigs, 50 mg, and for poultry, 8 mg. Daily use 1 time, use for 3~5 days. For sheep flukes, a large dose of 20 mg per kilogram of body weight is required for 6 days; for cattle flukes, a large dose of 2.5 to 10 mg per dry gram of body weight is required to achieve good results. It should be noted that cattle and sheep should stop taking medication 7 days before slaughter and release to avoid affecting the meat quality and being harmful to the human body.
[Application]
Fenbendazole is a new broad-spectrum veterinary anthelmintic. It is suitable for exterminating adults and larvae of gastrointestinal nematodes in cattle, horses, pigs and sheep. It has the advantages of wide anthelmintic spectrum, low toxicity, good tolerance, good palatability and wide safety range.
【Preparation】[3]
5-Phenylthio-2-nitroaniline is prepared from the reaction of 5-chloro-2-nitroaniline and benzenethiol, with a yield of 91%. After ferrous sulfate-iron powder reduction, 3-phenylthio-o-phenylenediamine was obtained with a yield of 90%. Finally, it is cyclized with S-methyl-cyanocarboxylic acid methyl ester to obtain thiobendazole.
[Main reference materials]
[1] Liu Shujun. New anti-helminthic drug─fenbendazole[J]. Jilin Animal Husbandry and Veterinary Medicine, 1998, 9: 025.
[2] Li Ya'e; Zhang Tingpan; Wang Guangxia. A method for preparing fenbendazole microspheres. CN201410702395.X, application date 2014-11-29
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