Allethrin I (R = −CH3)
Allethrin II (R = −COOCH3)

The allethrins are a group of related synthetic compounds used in insecticides. They are synthetic pyrethroids, a synthetic form of a chemical found naturally in the chrysanthemum flower. They were first synthesized in the United States by Milton S. Schechter in 1949. Allethrin was the first pyrethroid.

The compounds have low toxicity for humans and birds, and are used in many household insecticides such as RAID as well as mosquito coils. It is highly toxic to fish and aquatic invertebrates. At normal application rates, allethrin is slightly toxic to bees.[1] Insects subject to exposure become paralyzed (nervous system effect) before dying. Allethrins are toxic to cats[2] because they either do not produce, or produce less of certain isoforms of glucuronosyltransferase, which serve in hepatic detoxifying metabolism pathways.[3]

They are also used as an ultra-low volume spray for outdoor mosquito control.

Chemical structure

Allethrin I and allethrin II differ by having a methyl group and a methyl ester, respectively, on one terminus. Each of these allethrins consists of the eight possible stereoisomers. A partly enantiopure variant of allethrin I, consisting of only two stereoisomers in an approximate ratio of 1:1, is called bioallethrin. The same mixture of isomers, but in an approximate ratio of 3:1, is known as esbiothrin.


  1. "Pesticide Information Profile - Allethrin". External link in |publisher= (help)
  2. "Pyrethrin and Permethrin Toxicity in Dogs and Cats".
  3. Court, M. H.; Greenblatt, D. J. (2000). "Molecular genetic basis for deficient acetaminophen glucuronidation by cats: UGT1A6 is a pseudogene, and evidence for reduced diversity of expressed hepatic UGT1A isoforms". Pharmacogenetics. 10 (4): 355–369. doi:10.1097/00008571-200006000-00009. PMID 10862526.


External links

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