Permethrin is a synthetic pyrethroid insecticide and acaricide used to treat scabies, head lice, and as a topical insect repellent. It works by disrupting the sodium channels in nerve cell membranes of parasites, leading to paralysis and death. Permethrin is used both in pharmaceutical formulations (topical creams, lotions) and in agricultural or veterinary settings.
It exists as a mixture of cis and trans isomers, with the trans-isomer typically being more active.
Indications include (pharmaceutical use):
∙ Treatment of head lice (pediculosis capitis)
∙ Treatment of scabies
∙ Topical use for mites and lice in veterinary medicine
Parent: Permethrin
Parent: Permethrin
Impurities in permethrin originate from synthesis steps, including esterification of 3-phenoxybenzyl alcohol with acid chlorides, and from degradation due to light, heat, or oxidation. Impurity limits are regulated under ICH Q3A/B for human use and FAO/WHO or VICH guidelines for agricultural and veterinary applications.
Process-Related Impurities
Degradation Impurities
Elemental Impurities
Analytical Techniques for Impurity Detection
Permethrin is used to treat scabies and head lice in humans and as an insecticide in veterinary and agricultural settings. It is applied topically as a cream, lotion, or shampoo.
It acts on the nervous system of insects and mites, prolonging sodium channel activation, causing paralysis and death.
It is generally safe when used as directed, but ingestion, overuse, or improper application can cause neurotoxicity, especially in infants or pets.
Permethrin is sensitive to light and heat, particularly the cis-isomer. It should be stored in a cool, dark, and dry place in well-sealed containers.
