Washington Manual of Medical Therapeutics
Pyrethroids
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General Principles
The insecticidal properties of certain species of Chrysanthemum have been known for centuries. The flower secrets a compound called pyrethrum that targets sodium channels on the exoskeleton of insects.1 Permethrin is a synthetic derivative of pyrethrum that is the first-line treatment for scabies and lice as well as an insect repellent on bed nets and military uniforms.
Epidemiology
According to the AAPCC, pyrethroid exposures increased between 2000–2005, which corresponded with the phase out of organophosphate insecticides for residential use. Given the low toxicity of these agents, most outcomes resulted in no or minor symptoms.2
Clinical Presentation
History
It is rare that patients with permethrin exposures will present with acute symptoms as permethrin ingestions result in rapid hydrolysis. Additionally minimal toxicities arise when used dermally as prescribed. Occasionally, patients with complain of mild itching or dermatitis.3 Pyrethroid insecticides do not bioaccumulate and have virtually no chronic toxicity despite occasional news reports to the contrary. The NHANES study found no association between pyrethroid exposure and ADHD or learning disability in children.4
Physical Examination
Patients may have a mild case of dermatitis on examination.
Differential Diagnosis
Allergic dermatitis
Diagnostic Testing
None
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General Principles
The insecticidal properties of certain species of Chrysanthemum have been known for centuries. The flower secrets a compound called pyrethrum that targets sodium channels on the exoskeleton of insects.1 Permethrin is a synthetic derivative of pyrethrum that is the first-line treatment for scabies and lice as well as an insect repellent on bed nets and military uniforms.
Epidemiology
According to the AAPCC, pyrethroid exposures increased between 2000–2005, which corresponded with the phase out of organophosphate insecticides for residential use. Given the low toxicity of these agents, most outcomes resulted in no or minor symptoms.2
Clinical Presentation
History
It is rare that patients with permethrin exposures will present with acute symptoms as permethrin ingestions result in rapid hydrolysis. Additionally minimal toxicities arise when used dermally as prescribed. Occasionally, patients with complain of mild itching or dermatitis.3 Pyrethroid insecticides do not bioaccumulate and have virtually no chronic toxicity despite occasional news reports to the contrary. The NHANES study found no association between pyrethroid exposure and ADHD or learning disability in children.4
Physical Examination
Patients may have a mild case of dermatitis on examination.
Differential Diagnosis
Allergic dermatitis
Diagnostic Testing
None
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