Development of an Improved Method to Estimate the Days of Continuous Drug Ingestion Based on Micro-Segmental Hair Analysis

In a study from March 11, 2021, researchers improved a previously developed "micro-segmental hair analysis" method to estimate not only the day of single-dose drug ingestion but also the duration of continuous drug intake. Subjects ingested four hay-fever medications over periods ranging from 1 to 18 days, and chlorpheniramine was used as a single dose at intervals to serve as an internal temporal marker (ITM). By analyzing hair strands segmented into 0.4-mm pieces, the researchers could identify broad peaks in the distribution curves of the medications, which corresponded to the ingestion period. Using the ITM and the full width at half maximum (W2) of these peaks, they were able to estimate the first and final days of drug ingestion with an average error of approximately 2 days. This method shows promise for applications in drug-related crime investigations and therapeutic drug monitoring.