Incorporation of doxylamine and N-doxylamine-oxide in human hair and the impact of a permanent oxidative hair dye.

Abstract

Knowledge of the drug incorporation in hair and impact of cosmetic treatments remains essential to correctly interpret forensic cases. The study shows the analysis of doxylamine and doxylamine-N-oxide and the evaluation of the relationship between dose and hair concentration and the impact of hair treatment (oxidative dying). The study included (A) three subjects participated to the study: a regular user (Subject 1) and two single-dose users (Subject 2, 1 single dose; and Subject 3, 2 single doses spaced 5 months apart). Subject 3 applied a permanent oxidative hair dying monthly. (B) A permanent oxidative hair dying was applied twice to the hair collected from Subject 2. (A) The average concentrations in head hair for doxylamine and its N-doxylamine-oxide, respectively, were as follows: Subject 1, 1825 pg/mg and 16 pg/mg; Subject 2, 182 and <limit of quantification (LOQ); and Subject 3, Strand 1 (1 month after last single dose]; 1st cm: 367 pg/mg and 22 pg/mg; 2nd cm: 664 pg/mg and 37 pg/mg; 3rd cm 108 pg/mg and 13 pg/mg; 4th cm 13 pg/mg and 7 pg/mg); Strand 2 (5 months after last single dose: <LOQ). (B) The oxidative hair dying increased the concentration of the metabolite from undetected <LOQ up to 79 pg/mg (n = 3, RSD 6%). The concentration of the parent drug decreased from 128 pg/mg to 40 pg/mg (n = 3, RSD 4%). This is the first time the incorporation of doxylamine and its metabolite was evaluated with adequate and controlled information concerning dose and timing of ingestion for the evaluation of their incorporation and the impact of a cosmetic treatment.