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 dicoumarol (Hình ; Buckle và Smith 1994; Meehan 1986). Tất cả trong số đó là độc hại vì chúng hoạt động như thuốc chống đông máu, kéo dài thời gian đông máu và do đó gây ra xuất huyết. Các tính chất chống đông máu tự nhiên xảy ra dicoumarol đã được phát hiện tại Hoa Kỳ vào đầu thế kỷ 20, khi nó. | 11 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 Buckle and Smith 1994 Meehan 1986 . All of them are toxic because they act as anticoagulants extending the clotting time of blood and thus causing hemorrhaging. The anticoagulant properties of naturally occurring dicoumarol were discovered in the United States early in the 20th century when it was found to be the causal agent in cases of fatal hemorrhaging of cattle fed with 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 flo-coumafen 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 widespread use with time. 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 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 formulas of some ARs are given in Figure where it can be seen that they have some structural resemblance to both dicoumarol and vitamin K in its quinone form. All possess quinone rings .
