Proudfoot Alex T
National Poisons Information Service (Birmingham Centre), City Hospital, UK.
Toxicol Rev. 2005;24(2):107-13. doi: 10.2165/00139709-200524020-00004.
The pyrethrins have a long and fascinating history. They were derived from dried chrysanthemum flower heads that were found to have pesticidal activity centuries ago. They comprise a complex mixture of six main chemicals. Commercial formulations usually contain piperonyl butoxide, which inhibits metabolic degradation of the active ingredients. Pyrethrins are readily absorbed from the gut and respiratory tract but poorly absorbed through skin. The active components are rapidly and extensively metabolised in the liver. Pyrethrins probably act on sodium channels resulting in nervous system overactivity. The possibility that they also induce hypersensitivity, which may be fatal when the respiratory tract is involved, has been debated for many years. A few clinical reports support this suggestion but the limited epidemiological evidence available is against it. The number of reports of toxicity caused by pyrethrins has greatly decreased over recent years. The pyrethrins are generally of low acute toxicity but convulsions may occur if substantial amounts are ingested. Two deaths from acute asthma have been attributed to pyrethrins and clinical reports suggest that they may also cause a variety of forms of dermatitis. Ocular exposure has resulted in corneal erosions. Management of pyrethrin toxicity is supportive and symptomatic.
除虫菊酯有着悠久而迷人的历史。它们源自数百年前被发现具有杀虫活性的干菊花头。它们由六种主要化学物质组成的复杂混合物构成。商业配方通常含有胡椒基丁醚，它能抑制活性成分的代谢降解。除虫菊酯很容易从肠道和呼吸道吸收，但经皮肤吸收较差。活性成分在肝脏中迅速且广泛地代谢。除虫菊酯可能作用于钠通道，导致神经系统过度活跃。它们是否还会引发超敏反应（当涉及呼吸道时可能致命）这一问题已争论多年。一些临床报告支持这一观点，但现有的有限流行病学证据却与之相悖。近年来，由除虫菊酯引起的毒性报告数量大幅下降。除虫菊酯一般急性毒性较低，但如果大量摄入可能会发生惊厥。有两例急性哮喘死亡病例被归因于除虫菊酯，临床报告表明它们还可能导致多种形式的皮炎。眼部接触会导致角膜糜烂。除虫菊酯中毒的处理以支持治疗和对症治疗为主。
