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Forensic Toxicological Aspects of Tramadol: Focus on Enantioselective Drug Disposition and Pharmacogenetics
Linköping University, Department of Medical and Health Sciences, Division of Drug Research. Linköping University, Faculty of Medicine and Health Sciences.
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

One of the most difficult parts in forensic toxicology is to interpret obtained drug concentrations. Was it therapeutic, toxic or even lethal to the particular individual that the blood sample was drawn from? Concentrations of opioid drugs are especially difficult to interpret, because of large interindividual differences in innate and acquired tolerance.

Tramadol is a complex drug. Not only is it an opioid, it is also a racemic drug with the (+)- and (-)-enantiomers of the parent compound and metabolites showing different pharmacological effects. Further, it is metabolized by polymorphic enzymes, which may affect the amounts of metabolites formed and possibly the enantiomer ratios of the parent compound and its metabolites. It has been speculated that particularly the (+)/(-)-enantiomer ratio of O-desmethyltramadol is related to the risk of adverse effects, and it has been shown that the ratio is affected by CYP2D6 genotype.

The overall aim of the thesis was to evaluate if forensic interpretations of tramadol, regarding toxicity and time since drug administration, may be improved by the use of genotyping and enantioselective concentration determination of tramadol and its three main metabolites.

To simultaneously quantify the enantiomer concentrations of tramadol, Odesmethyltramadol, N-desmethyltramadol and N,O-didesmethyltramadol in whole blood, a liquid chromatography tandem mass spectrometry (LCMS/MS) method was developed and validated. Genetic variation in CYP2D6, CYP2B6, CYP3A4 (encoding the tramadol metabolizing enzymes), ABCB1 (encoding a transport protein) and OPRM1 (encoding the μ-opioid receptor) was investigated, using pyrosequencing, xTAG, and TaqMan analysis. The methods were applied to the blood samples of two study populations; 19 healthy volunteers administered a therapeutic, single tramadol dose, and 159 tramadol positive autopsy cases.

The most important finding was the positive correlations between all four enantiomer ratios and time since tramadol administration in the healthy volunteers. All enantiomer ratios except the one of tramadol was also affected by the CYP2D6 genotype, which was apparent among the autopsy cases as well. Genetic variation in CYP2D6 and possibly CYP2B6 was shown to have an impact on tramadol pharmacokinetics, although no association to neither drug related symptoms nor tramadol related causes of death was found. Tramadol intoxications were predominantly characterized by low age (median 26 years) and male sex, often with a history of substance abuse and with other drugs (at fairly low concentrations) detected in blood.

In conclusion, enantiomer concentration determination combined with genotyping seems promising regarding estimations of time since drug administration, although is of low value concerning interpretations of toxicity in autopsy cases.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2018. , p. 104
Series
Linköping University Medical Dissertations, ISSN 0345-0082 ; 1647
National Category
Pharmaceutical Sciences Forensic Science
Identifiers
URN: urn:nbn:se:liu:diva-152626DOI: 10.3384/diss.diva-152626ISBN: 9789176851968 (print)OAI: oai:DiVA.org:liu-152626DiVA, id: diva2:1262029
Public defence
2018-11-30, Berzeliussalen, Campus US, Linköping, 13:00 (English)
Opponent
Supervisors
Available from: 2018-11-09 Created: 2018-11-09 Last updated: 2019-09-30Bibliographically approved
List of papers
1. Pharmacogenetic aspects of tramadol pharmacokinetics and pharmacodynamics after a single oral dose
Open this publication in new window or tab >>Pharmacogenetic aspects of tramadol pharmacokinetics and pharmacodynamics after a single oral dose
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2014 (English)In: Forensic Science International, ISSN 0379-0738, E-ISSN 1872-6283, Vol. 238, p. 125-132Article in journal (Refereed) Published
Abstract [en]

The major purpose of this study was to elucidate if genotyping can facilitate interpretations of tramadol (TRA) in forensic case work, with special regard to the estimation of the time of drug intake and drug related symptoms (DRS). The association between genetic polymorphisms in CYP2D6, OPRM1 and ABCB1 and pharmacokinetic and pharmacodynamic properties of TRA was studied. Nineteen healthy volunteers were randomized into two groups receiving a single dose of either 50 or 100 mg of orally administrated TRA. Blood samples were collected prior to dosing and up to 72 h after drug intake. The subjects were asked to report DRS during the experimental day. We found a positive correlation between the metabolic ratio of O-desmethyltramadol (ODT) to TRA and the time after drug intake for both CYP2D6 intermediate metabolizers and extensive metabolizers. For the only poor metabolizer with detectable ODT levels the metabolic ratio was almost constant. Significant associations were found between the area under the concentration-time curve (AUC) and three of the investigated ABCB1 single nucleotide polymorphisms for TRA, but not for ODT and only in the 50 mg dosage group. There was great interindividual variation in DRS, some subjects exhibited no symptoms at all whereas one subject both fainted and vomited after a single therapeutic dose. However, no associations could be found between DRS and investigated polymorphisms. We conclude that the metabolic ratio of ODT/TRA may be used for estimation of the time of drug intake, but only when the CYP2D6 genotype is known and taken into consideration. The influence of genetic polymorphisms in ABCB1 and OPRM1 requires further study.

Place, publisher, year, edition, pages
Elsevier, 2014
Keywords
Tramadol; Pharmacokinetics; Pharmacodynamics; CYP2D6; ABCB1; OPRM1
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-106838 (URN)10.1016/j.forsciint.2014.03.003 (DOI)000334580700025 ()24709712 (PubMedID)
Available from: 2014-05-28 Created: 2014-05-23 Last updated: 2018-11-09Bibliographically approved
2. Quantitation of the enantiomers of tramadol and its three main metabolites in human whole blood using LC-MS/MS.
Open this publication in new window or tab >>Quantitation of the enantiomers of tramadol and its three main metabolites in human whole blood using LC-MS/MS.
2016 (English)In: Journal of Pharmaceutical and Biomedical Analysis, ISSN 0731-7085, E-ISSN 1873-264X, Vol. 119, p. 1-9Article in journal (Refereed) Published
Abstract [en]

The analgesic drug tramadol and its metabolites are chiral compounds, with the (+)- and (-)-enantiomers showing different pharmacological and toxicological effects. This novel enantioselective method, based on LC-MS/MS in reversed phase mode, enabled measurement of the parent compound and its three main metabolites O-desmethyltramadol, N-desmethyltramadol and N,O-didesmethyltramadol simultaneously. Whole blood samples of 0.5g were fortified with internal standards (tramadol-(13)C-D3 and O-desmethyl-cis-tramadol-D6) and extracted under basic conditions (pH 11) by liquid-liquid extraction. Chromatography was performed on a chiral alpha-1-acid glycoprotein (AGP) column preceded by an AGP guard column. The mobile phase consisted of 0.8% acetonitrile and 99.2% ammonium acetate (20mM, pH 7.2). A post-column infusion with 0.05% formic acid in acetonitrile was used to enhance sensitivity. Quantitation as well as enantiomeric ratio measurements were covered by quality controls. Validation parameters for all eight enantiomers included selectivity (high), matrix effects (no ion suppression/enhancement), calibration model (linear, weight 1/X(2), in the range of 0.25-250ng/g), limit of quantitation (0.125-0.50ng/g), repeatability (2-6%) and intermediate precision (2-7%), accuracy (83-114%), dilution integrity (98-115%), carry over (not exceeding 0.07%) and stability (stable in blood and extract). The method was applied to blood samples from a healthy volunteer administrated a single 100mg dose and to a case sample concerning an impaired driver, which confirmed its applicability in human pharmacokinetic studies as well as in toxicological and forensic investigations.

Keywords
Enantiomer; LC–MS/MS; N, O-didesmethyltramadol; N-desmethyltramadol; O-desmethyltramadol; Tramadol
National Category
Analytical Chemistry
Identifiers
urn:nbn:se:liu:diva-125284 (URN)10.1016/j.jpba.2015.11.012 (DOI)000370211900001 ()26625281 (PubMedID)
Note

Funding agencies:The National Board of Forensic Medicine in Sweden funded this work.

Available from: 2016-02-19 Created: 2016-02-19 Last updated: 2018-11-09
3. Enantioselective pharmacokinetics of tramadol and its three main metabolites; impact of CYP2D6, CYP2B6, and CYP3A4 genotype
Open this publication in new window or tab >>Enantioselective pharmacokinetics of tramadol and its three main metabolites; impact of CYP2D6, CYP2B6, and CYP3A4 genotype
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2018 (English)In: Pharmacology Research & Perspectives, ISSN 2052-1707, Vol. 6, no 4, article id e00419Article in journal (Refereed) Published
Abstract [en]

Tramadol is a complex drug, being metabolized by polymorphic enzymes and administered as a racemate with the (+)- and (-)-enantiomers of the parent compound and metabolites showing different pharmacological effects. The study aimed to simultaneously determine the enantiomer concentrations of tramadol, O-desmethyltramadol, N-desmethyltramadol, and N,O-didesmethyltramadol following a single dose, and elucidate if enantioselective pharmacokinetics is associated with the time following drug intake and if interindividual differences may be genetically explained. Nineteen healthy volunteers were orally administered either 50 or 100 mg tramadol, whereupon blood samples were drawn at 17 occasions. Enantiomer concentrations in whole blood were measured by LC-MS/MS and the CYP2D6,CYP2B6 and CYP3A4 genotype were determined, using the xTAG CYP2D6 Kit, pyrosequencing and real-time PCR, respectively. A positive correlation between the (+)/(-)-enantiomer ratio and time following drug administration was shown for all four enantiomer pairs. The largest increase in enantiomer ratio was observed for N-desmethyltramadol in CYP2D6 extensive and intermediate metabolizers, rising from about two to almost seven during 24 hours following drug intake. CYP2D6 poor metabolizers showed metabolic profiles markedly different from the ones of intermediate and extensive metabolizers, with large area under the concentration curves (AUCs) of the N-desmethyltramadol enantiomers and low corresponding values of the O-desmethyltramadol and N,O-didesmethyltramadol enantiomers, especially of the (+)-enantiomers. Homozygosity of CYP2B6 *5 and *6 indicated a reduced enzyme function, although further studies are required to confirm it. In conclusion, the increase in enantiomer ratios over time might possibly be used to distinguish a recent tramadol intake from a past one. It also implies that, even though (+)-O-desmethyltramadol is regarded the enantiomer most potent in causing adverse effects, one should not investigate the (+)/(-)-enantiomer ratio of O-desmethyltramadol in relation to side effects without consideration for the time that has passed since drug intake.

Place, publisher, year, edition, pages
John Wiley & Sons, 2018
National Category
Pharmaceutical Sciences
Identifiers
urn:nbn:se:liu:diva-152586 (URN)10.1002/prp2.419 (DOI)000442994300006 ()29992026 (PubMedID)2-s2.0-85052511964 (Scopus ID)
Available from: 2018-11-09 Created: 2018-11-09 Last updated: 2018-12-03Bibliographically approved

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