Micro-Segmental Analysis of the Entry Pathway and Distribution of Zolpidem in Hair From Different Scalp Regions After a Single Dose

In a study analyzing zolpidem distribution in hair after a single oral dose, researchers used a micro-segmental LC-MS/MS method to examine 0.4 mm hair segments from three subjects. Hair samples were collected from the vertex posterior at 1, 3, 7, and 28 days post-administration, and from the parietal, left temporal, and right temporal regions at 28 days. The highest zolpidem concentration (1.5-2.4 pg/mm) was found in the 0-0.4 mm segment of hair plucked at 1 day, with concentrations decreasing over time and disappearing by 28 days. This pattern suggests initial drug incorporation through the bloodstream into the hair follicle, followed by movement towards the hair tip. The presence of two concentration peaks in the hair suggests entry from both blood and external secretions like sweat and sebum. Zolpidem was consistently detected in the vertex posterior region, making it a reliable site for drug intake estimation, while detection was less consistent in other scalp regions.