Dermal absorption of permethrin following topical administration

Area of Science:

• Pharmacology
• Toxicology
• Dermatology

Background:

• Permethrin is a widely used topical insecticide for treating lice and scabies.
• While effective, comprehensive pharmacokinetic data for topical permethrin are limited.
• Understanding systemic exposure is crucial for assessing safety.

Purpose of the Study:

• To determine the systemic exposure of permethrin after topical application.
• To investigate the duration of permethrin's presence in the human body.
• To provide pharmacokinetic data supporting the safety of topical permethrin.

Main Methods:

• Three study parts involving healthy men and scabies patients applying permethrin formulations (ethanolic solution or cream) to the skin.
• Urine collection for up to 168 hours post-application.
• Quantification of permethrin's main metabolite and its conjugates using gas chromatography/electron capture detection.

Main Results:

• Pharmacokinetics were consistent across all study groups.
• Mean terminal elimination half-life ranged from 28.8 to 37.8 hours.
• Urinary recovery of the permethrin metabolite was low, ranging from 0.35 to 0.52 M percent of the applied dose.
• The treatment was well tolerated by participants.

Conclusions:

• Systemic exposure to permethrin following topical therapeutic administration is minimal.
• Permethrin is largely eliminated from the body within one week.
• These findings provide a pharmacokinetic basis for the established clinical safety of topical permethrin formulations.