title: Sequencing CYP2D6 for the detection of poor-metabolizers in post-mortem blood samples with tramadol.
abstract: Tramadol concentrations and analgesic effect are dependent on the CYP2D6 enzymatic activity. It is well known that some genetic polymorphisms are responsible for the variability in the expression of this enzyme and in the individual drug response. The detection of allelic variants described as non-functional can be useful to explain some circumstances of death in the study of post-mortem cases with tramadol. A Sanger sequencing methodology was developed for the detection of genetic variants that cause absent or reduced CYP2D6 activity, such as *3, *4, *6, *8, *10 and *12 alleles. This methodology, as well as the GC/MS method for the detection and quantification of tramadol and its main metabolites in blood samples was fully validated in accordance with international guidelines. Both methodologies were successfully applied to 100 post-mortem blood samples and the relation between toxicological and genetic results evaluated. Tramadol metabolism, expressed as its metabolites concentration ratio (N-desmethyltramadol/O-desmethyltramadol), has been shown to be correlated with the poor-metabolizer phenotype based on genetic characterization. It was also demonstrated the importance of enzyme inhibitors identification in toxicological analysis. According to our knowledge, this is the first study where a CYP2D6 sequencing methodology is validated and applied to post-mortem samples, in Portugal. The developed methodology allows the data collection of post-mortem cases, which is of primordial importance to enhance the application of these genetic tools to forensic toxicology and pathology.
authors.affiliation: National Institute of Legal Medicine and Forensic Sciences, Portugal. Electronic address: suzana.m.fonseca@inmlcf.mj.pt.
authors.forename: Suzana
authors.initials: S
authors.lastname: Fonseca
authors.affiliation: National Institute of Legal Medicine and Forensic Sciences, Portugal.
authors.forename: António
authors.initials: A
authors.lastname: Amorim
authors.affiliation: National Institute of Legal Medicine and Forensic Sciences, Portugal.
authors.forename: Heloísa Afonso
authors.initials: HA
authors.lastname: Costa
authors.affiliation: National Institute of Legal Medicine and Forensic Sciences, Portugal.
authors.forename: João
authors.initials: J
authors.lastname: Franco
authors.affiliation: National Institute of Legal Medicine and Forensic Sciences, Portugal.
authors.forename: Maria João
authors.initials: MJ
authors.lastname: Porto
authors.affiliation: National Institute of Legal Medicine and Forensic Sciences, Portugal.
authors.forename: Jorge Costa
authors.initials: JC
authors.lastname: Santos
authors.affiliation: National Institute of Legal Medicine and Forensic Sciences, Portugal.
authors.forename: Mário
authors.initials: M
authors.lastname: Dias
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D019389:Cytochrome P-450 CYP2D6 / Q000235:genetics*; D053593:Forensic Toxicology; D006801:Humans; D008297:Male; D008875:Middle Aged; D009294:Narcotics / Q000097:blood / Q000506:poisoning*; D010597:Pharmacogenetics; D011041:Poisoning / Q000175:diagnosis; D020641:Polymorphism, Single Nucleotide; D011174:Portugal; D011180:Postmortem Changes; D014147:Tramadol / Q000097:blood / Q000506:poisoning*
chemical_list: D009294:Narcotics; D014147:Tramadol; D019389:Cytochrome P-450 CYP2D6
keywords: CYP2D6; Forensic toxicology; Pharmacogenetics; Poor metabolizers; Post-mortem; Tramadol