Issues About Axial Diffusion During Segmental Hair Analysis
May 2013
in “
Therapeutic drug monitoring
”
TLDR Wait 4-5 weeks after drug use before hair testing and cut hair into three segments to confirm single drug exposure.
The document discussed the challenges of interpreting drug exposure results from segmental hair analysis, particularly when drugs are detected in multiple consecutive hair segments. Based on 20 years of experience and literature review, the author suggested waiting 4-5 weeks post-event before collecting hair samples and segmenting them into 2 cm sections. A single drug dose should primarily appear in the proximal segment. However, drugs sometimes appear in multiple segments due to axial diffusion, sweat, and other secretions, or cosmetic treatments. To confirm single exposure, the highest drug concentration should be in the segment corresponding to the event period and be at least 3 times higher than adjacent segments.
