Doxylamine pharmacokinetics following single dose oral administration in children ages 2-17 years

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

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 Collapse

Key Words

• N-doxylamine-oxide
• cosmetic treatment
• doxylamine
• hair
• interpretation

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Affiliation(s)

Maria Del Mar Ramirez Fernandez Department of Toxicology, National Institute of Criminalistics and Criminology, Brussels, Belgium
Sarah M R Wille Department of Toxicology, National Institute of Criminalistics and Criminology, Brussels, Belgium
Nele Samyn Department of Toxicology, National Institute of Criminalistics and Criminology, Brussels, Belgium

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Single-Dose Pharmacokinetic Study of Diphenhydramine HCl in Children and Adolescents

Diphenhydramine pharmacokinetics were characterized following a single oral dose in children aged 2 to 17 years using a weight- and age-based dosing schedule with more tiers than the current age-based dosing schedule recommended by the nonprescription drug monograph. This study was conducted in 42 subjects, aged 2 to 17 years. Doses were based on a weight-age dosing schedule, ranging from 6.25 to 50 mg. An oral dose was administered with water about 2 hours after a light breakfast. Plasma samples were obtained up to 48 hours after dosing and analyzed for diphenhydramine. Pharmacokinetic parameters were estimated using noncompartmental methods, and the relationship of oral clearance with age was assessed using linear regression. Over an 8-fold range of doses, C_max and AUC increased ∼90 % to ∼140% across age groups, with a similar T_max (1.5 hours). Oral CL/F increased with age, but after allometric scaling, no maturation-related change in CL/F was apparent. Mild somnolence was the most commonly reported adverse event (95% of the subjects). A weight-age dosing schedule using an 8-fold range of doses achieved C_max and AUC that increased about 2-fold across age groups. No effect of maturation on CL/F was observed after allometric scaling.