Distribution profiles of diphenhydramine and lidocaine in scalp, axillary, and pubic hairs measured by micro-segmental hair analysis: good indicator for discrimination between administration and external contamination of the drugs

Abstract

Purpose Drug 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. Methods A 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. Results The 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. Conclusions Micro-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.

Micro-segmental hair analysis: detailed procedures and applications in forensic toxicology

“…A hair strand is cut at sub-millimeter intervals, and each segment analyzed independently (Fig. 1) [15][16][17][23][24][25][26][27][28]. The distribution profile shows a smooth curve as compared to that in the conventional segmental analysis.…”

“…In the analytical conditions adopted by Kuwayama et al [15][16][17][23][24][25][26][27][28], the time required for instrumental analysis was 7 min/sample, consisting of 2 min for large-volume injection and 5 min for MS measurement. Hence, sequential analysis of 192 samples in two 96-well plates, corresponding to a 7.68-cm hair strand, was completed in 22.4 h.…”

“…However, the distal peak was dominant for methylephedrine (ME) and lidocaine (LD) (Fig. 6) [16,28]. Although the difference may be due to differential drug transfer into sweat and sebum depending on the chemical properties of the drugs and physiological states of tissues surrounding the scalp hair.…”

“…A single hair strand was collected from the scalp several weeks after the drug administration. The figure quoted from [28] was modified for this figure. DDP desmethyldiphenhydramine, DLD desethyllidocaine and ITM peaks was measured.…”

“…8d). The proximal end of the high-concentration region corresponds to the time at which the hair is in contact with the drug [28]. The drug is not detected in the proximal hair root region because the region has not yet been produced or was under the skin during the contact time.…”