Insecticides of Pyrethrin and Pyrethroid

The pyrethrin insecticides were discovered in the last decade of the 19th century. They are marketed under the names pyrethrum, pyrethrin and pyrethroid.

Pyrethrin is the oleoresin of the dried chrysanthemum flower. The resin contains several esters with insecticidal acridity, comprising approximately 50% of the ingredients. Pyrethrins have been used as insecticides for centuries.

In the United States, reports to poison centers regarding pyrethroid exposure have been quantitatively similar to reports regarding organophosphate insecticide, but with the fewer clinically important poisonings.

The word pyrethrin is a general term used for each of the six naturally occurring insecticidal compounds in pyrethrum.

Pyrethrum insecticide is a crude alcoholic extract of plants from members of the Compositae family such as chrysanthemums or daisies. Pyrethrum contains a variable mixture of the six specific pyrethrins:
cinerin I
cinerin II
jasmolin I
jasmolin II
pyrethrin I
pyrethrin II

Pyrethrin is a more refined extract of Compositae plants as well as the chemical name of the true insecticide inside pyrethrum. Whereas pyrethrum is about 67% pure pyrethrin, the compound market specifically as pyrethrin is close to 97% pyrethrin.

Pyrethroid, of which there are many forms, is the name given to the synthetic forms of pyrethrin. Pyrethroids are lipophilic and are absorbed, to some degree, via intact skin, lungs or intestinal tract.

Depending on the specific pyrethrin or pyrethroid this absorption may a minor or a major route of absorption.

Skin absorption is slow. Depending on the magnitude of the dose however, the skin is the major pathway of poisoning. When pyrethroids enter the vascular compartment, their half lives range from hours to days.
Insecticides of Pyrethrin and Pyrethroid