Related Experiment Video
Updated: Apr 15, 2026

Validated LC-MS/MS Panel for Quantifying 11 Drug-Resistant TB Medications in Small Hair Samples
Published on: May 19, 2020
Individual variations of amitriptyline biotransformation examined in scalp hair samples
Detlef Thieme1, Dagmar Schmid, Hans Sachs
1Institute of Forensic Medicine, Frauenlobstr. 7a, 80337, Munich, Germany, det.thieme@web.de.
Abstract:
The identification of amitriptyline, nortriptyline and its hydroxy-metabolites including a subsequent measurement of concentration profiles in hair samples was carried out to evaluate the administration history of amitriptyline. Analyses were carried out using liquid chromatography-tandem mass spectrometry, which permits simultaneous identification of all relevant substances in hair at low target concentrations (limit of detection better than 0.5 pg/mg). Standard hair sample preparation was applied for the estimation of average substance concentration in a hair bundle, while segmentation of individual hairs was utilised to examine accurate concentration profiles. Replication of analyses demonstrated a good reproducibility of individual hair concentration profiles, which proved to coincide for all relevant compounds. Significant variations of metabolite ratios (e.g. nortriptyline to amitriptyline and E10- to Z10-hydroxynortriptyline) between individuals suggest a correlation between hair concentration and metabolic phenotype. Different concentration ratios of certain metabolites in hair are highly correlated, indicating a systematic association between demethylation and stereo-specificity of hydroxylation. The trans isomers of hydroxy-metabolites become significantly more prevalent with increasing degree of demethylation of amitriptyline or hydroxylation of amitriptyline.
Related Concept Videos
Pharmacogenetics of Phase II Enzymes: N-acetyltransferase, Thiopurine S-methyltransferase, UDP-glucuronosyltransferase
Pharmacogenetics of Drug Targets: β₂-Adrenergic Receptors, Apo E, Thymidylate Synthase
Pharmacogenetic Phenotypes: Alterations in Pharmacokinetics, Drug Targets and Biologic Milieu
Factors Affecting Drug Biotransformation: Biological
Species differences: Variations in enzyme systems across species can cause disparities in drug metabolism. For instance, humans may metabolize certain drugs faster than rodents, altering therapeutic effects.
Strain differences: Genetic variations within a species can result in differing enzyme activity, impacting drug response and toxicity. For example, some mouse strains may...
Drug toxicity: Idiosyncratic Reactions
Bioequivalence of Drugs: Drugs with Multiple Indications

