Abstract
PurposeDrug distribution in scalp hair can provide historical information about drug use, such as the date and frequency of drug ingestion. We previously developed micro-segmental hair analysis, which visualizes drug distribution at 0.4-mm intervals in individual hairs. The present study examines whether the distribution profiles of drugs can be markers for the administration or external contamination of the drugs using scalp, axillary, and pubic hairs.MethodsA single dose of anti-itch ointment containing diphenhydramine (DP) and lidocaine (LD) was topically applied to the axillary or pubic areas of two volunteers; DP was also orally administered; and LD was intra-gingivally injected. Scalp, axillary, and pubic hairs were assessed using our micro-segmental analysis.ResultsThe localization of DP and LD differed within individual scalp hair strands, implying DP and LD were predominantly incorporated into scalp hair via the bloodstream and via sweat/sebum, respectively, showing double-peak profiles. However, DP and LD were distributed along the shafts of axillary and pubic hairs without appearance of the double-peak profiles when the ointment had been applied to the axillary and pubic areas. The distributions of DP and LD in scalp hairs did not significantly differ according to administration routes, such as oral administration, gingival injection, and topical application.ConclusionsMicro-segmental analysis revealed differences in the distribution profiles of drugs in hairs, and distinguished hairs with and without external contamination. These findings will be useful for understanding of the mechanism of drug uptake into hair and for estimating the circumstances for a drug use.
Highlights
Understanding how a drug is administered is important to elucidate the circumstances of drug-related crimes during investigations
The values of concentrations at the root (CR) and CT for any analyte significantly differed between individual hair strands, regardless of the administration route
Routes of uptake into scalp hair differ depending on administered drugs We previously showed that CP and ME are located at different positions in strands of scalp hair even when simultaneously ingested [12]
Summary
Understanding how a drug is administered is important to elucidate the circumstances of drug-related crimes during investigations. The choice of administration route affects the time course of drug concentrations in the blood and can change the duration of pharmacological effects. One method of estimating routes of drug administration is to monitor blood drug concentrations [6, 7]. This requires obtaining many blood samples for several days soon after drug administration. This is not practical in criminal investigations because biological specimens from suspects or victims are usually collected only once after an incident is brought to the attention of police, which can be a long time after the drug ingestion. Hair has a potential to estimate drug administration routes because information about the time course of drug concentration may be recorded in individual hair strands for several months or more [8,9,10]
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