Warfarin, đã được giới thiệu ra thị trường vào cuối những năm 1940, là người đầu tiên của một loạt các thuốc diệt loài gặm nhấm thuốc kháng đông (ARS) có liên quan trong cấu trúc để dicoumarol (Hình ) (Meehan, 1986; Buckle và Smith, 1994). Tất cả đều độc hại bởi vì họ hành động như thuốc chống đông máu kéo dài thời gian đông máu và vì vậy gây ra xuất huyết. Các tính chất chống đông máu của dicoumarol tự nhiên đã được phát hiện ở Mỹ vào đầu thế kỷ hai mươi, khi nó được phát. | CHAPTER 11 The anticoagulant rodenticides Background Warfarin which was introduced to the market in the late 1940s was the first of a series of anticoagulant rodenticides ARs related in structure to dicoumarol Figure Meehan 1986 Buckle and Smith 1994 . All of them are toxic because they act as anticoagulants extending the clotting time of blood and so causing haemorrhaging. The anticoagulant properties of naturally occurring dicoumarol were discovered in the USA early in the twentieth century when it was found to be the causal agent in cases of fatal haemorrhaging of cattle that had been fed spoiled clover. Subsequently it was discovered that dicoumarol and rodenticides related to it have anticoagulant action because they act as vitamin K antagonists. For some years warfarin was by far the most widely used rodenticide of this type. In time however strains of rats resistant to warfarin began to appear and the compound became ineffective in some areas where it had been regularly used. Resistance was overcome at least in the short term by a second generation of ARs sometimes called superwarfarins . Examples include brodifacoum difenacoum flocoumafen and bromodiolone. The superwarfarins are more hydrophobic persistent and toxic than warfarin itself. They have usually been effective in overcoming resistance to warfarin and consequently have come into more wide-scale use in the last two decades. Although knowledge about their environmental fate and effects is at present very limited enough is known to raise questions about the risks that might be associated 2001 C. H. Walker The anticoagulant rodenticides 205 with their increasing use. The combination of persistence with very high vertebrate toxicity has set the alarm bells ringing. The ensuing account will be principally concerned with the second-generation rodenticides. Chemical properties The formulae of some ARs are given in Figure where it can be seen that they have some structural resemblance .

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