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Therapeutic Drug Monitoring of Escitalopram in an outpatient setting
Linköping University, Department of Medicine and Care, Clinical Pharmacology. Linköping University, Faculty of Health Sciences.ORCID iD: 0000-0002-6041-0744
Linköping University, Department of Medicine and Care, Clinical Pharmacology. Linköping University, Faculty of Health Sciences.
Linköping University, Department of Medicine and Care, Clinical Pharmacology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre for Laboratory Medicine, Department of Clinical Pharmacology.
Linköping University, Department of Medicine and Care, Clinical Pharmacology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre for Laboratory Medicine, Department of Clinical Pharmacology.
2007 (English)In: Therapeutic Drug Monitoring, ISSN 0163-4356, E-ISSN 1536-3694, Vol. 29, no 6, 758-766 p.Article in journal (Refereed) Published
Abstract [en]

The main objectives of this study were to outline the inter- and intraindividual and overall pharmacokinetic variability of S-citalopram, S-desmethylcitalopram, and S-didesmethylcitalopram in serum by means of therapeutic drug monitoring, and to investigate potential correlations between the serum concentration and simultaneously collected clinical data. The study was conducted on outpatients in Sweden in 2002 to 2005. Included in the pharmacokinetic evaluation were 155 patients (68% women and 32% men) aged 17 to 95 years (average, 51 years). One serum sample per patient, taken as a trough value in steady state, was assessed. For the inter- and intraindividual variation calculation, 16 patients were included with two eligible samples each. The median daily dose was 20 mg/day (range, 5-40 mg). Extensive overall serum concentration variability was seen for all dose levels. The interindividual coefficient of variation for dose-normalized concentrations was 71% for S-citalopram, 36% for S-desmethylcitalopram, and 50% for S- didesmethylcitalopram. The intraindividual variations over time for the same parameters were approximately 30%, except for the ratio S-desmethylcitalopram/S- citalopram, which was 23%. The median S-desmethylcitalopram level was approximately 60% of the parent substance and the S-didesmethylcitalopram level approximately 9%. Higher age was correlated with higher serum concentrations, but no gender-related concentration differences were found. A majority (76%) of the patients took one or more drugs in addition to escitalopram, but concomitant medication did not seem to interact with escitalopram. However, women taking oral contraceptives showed a lower metabolic ratio compared with age-matched women. As a result of the wide range of the ratio in this population, these findings are not considered of clinical relevance.

Place, publisher, year, edition, pages
2007. Vol. 29, no 6, 758-766 p.
Keyword [en]
Escitalopram, Serum concentration, SSRI, Therapeutic drug monitoring
National Category
Medical and Health Sciences
Identifiers
URN: urn:nbn:se:liu:diva-41188DOI: 10.1097/FTD.0b013e31815b3f62Local ID: 55316OAI: oai:DiVA.org:liu-41188DiVA: diva2:262039
Available from: 2009-10-10 Created: 2009-10-10 Last updated: 2017-12-13Bibliographically approved
In thesis
1. Therapeutic Drug Monitoring in Psychiatry: Some aspects of utility in clinical practice and research
Open this publication in new window or tab >>Therapeutic Drug Monitoring in Psychiatry: Some aspects of utility in clinical practice and research
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Background and objectives: Several new psychoactive drugs for the treatment of psychiatric disorders have been introduced onto the market since the late 1980s. Basic aspects of pharmacodynamics and pharmacokinetics (PK) are investigated before approval for general prescription. Thus, a limited number of subjects are exposed to the drug before it is marketed and only sparse measurements of drug concentration are performed during phases II and III of drug development. The objective of this thesis was to provide further descriptive PK and linked patients data in naturalistic clinical settings. The PK of psychoactive drugs was also studied in the elderly and the young, major risk groups that are exposed in normal everyday clinical practice but that are underrepresented in the phases of drug development. The PK-data were to be assessed by samples sent to the Therapeutic Drug Monitoring (TDM) laboratory service. In a subset of individuals, the genotypes of the cytochrome P450 (CYP) enzymes were described.

Results: Serum concentration of the parent compound and its metabolites was provided from TDM-data on antidepressant escitalopram (Paper I) and antipsychotic ziprasidone (Paper II). A large interindividual PK variability was found. The daily dose of the drug was higher than the defined daily dose (DDD) for both escitalopram and ziprasidone (median dose 20 mg and 120 mg, respectively). The median number of drugs per patient, apart from the studied drug, was 4 and 3, respectively (range 1-18). If repeated eligible TDM-data were available, change in treatment strategies could be seen between the first and second sample for the patient, and the metabolite/parent compound (M/P) ratio had lower intraindividual than interindividual variation in the escitalopram study but opposite results were found in the ziprasidone study.

The prescription of antidepressant drugs (ADs) in the nursing homes studied was 38 % (Paper III). The concentration of the ADs was higher, or much higher, than could be expected from the dose administered in 73 %. The majority of the elderly people were treated with citalopram. No clear time schedule for how long the drug treatment should continue was found in the patients’ current medical record. The median number of drugs per patient apart from the AD was 11 (range 4-19), no monotherapy was found in these patients. The genetically impaired metabolic activity of CYP enzymes correlated to higher drug concentration as expected, in patients medicated with an AD that is substrate for the CYP enzyme genotype.

The concentrations of ADs were as expected from the dose administered in 63 % of the children/adolescents evaluated (Paper IV). The majority of TDM samples requested sertraline. PK outcome of sertraline was similar to the results in adult populations. Monotherapy was documented in 49 % (median number of drugs apart from AD was 1 per patient, range 1-7). Changes in treatment strategies were also shown, if repeated TDM-samples were available. The median variation of the M/P ratio for sertraline between the first and the last samples within the same patient was 20 % (the interindividual variation was 37 %). The poor metabolizers (PM) for CYP2D6 medicated with a CYP2D6 substrate had a lower dose than did non-PM for the same drug.

Conclusion: These studies provide reference data for the evaluation of the therapeutic response, i.e. a reference range of what is to be expected in a normal clinical setting, as well as the toxicological information concerning the psychoactive drugs studied. When available, the M/P ratio between two patients’ samples may assess patient compliance, as well as drug-drug interactions. Thus, the use of TDM can be beneficial for individual dose optimisation and drug safety, above all in the studied populations, elderly people and children/adolescents, when the selection of doses requires a consideration of PK parameters. TDM may be a tool for research, increasing knowledge of the psychoactive drug in TDM service, as well as toxicology. A more frequent clinical use of TDM and pharmacogenetic testing in clinical practice would contribute to a better quality when treating with psychoactive drugs.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2009. 84 p.
Series
Linköping University Medical Dissertations, ISSN 0345-0082 ; 1152
Keyword
TDM, psychoactive drug, pharmacokinetics, pharmacogenetics, naturalistic, elderly, child
National Category
Pharmacology and Toxicology
Identifiers
urn:nbn:se:liu:diva-52107 (URN)978-91-7393-537-1 (ISBN)
Public defence
2009-12-18, Berzeliussalen, Hälsouniversitetet, Campus US, Linköpings universitet, Linköping, 09:00 (Swedish)
Opponent
Supervisors
Available from: 2009-12-07 Created: 2009-12-04 Last updated: 2009-12-07Bibliographically approved

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Reis, MargaretaCherma Yeste, Maria DoloresCarlsson, BjörnBengtsson, Finn

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