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van der Heijden LT, Opdam FL, Beijnen JH, Huitema ADR. The Use of Microdosing for In vivo Phenotyping of Cytochrome P450 Enzymes: Where Do We Stand? A Narrative Review. Eur J Drug Metab Pharmacokinet 2024; 49:407-418. [PMID: 38689161 PMCID: PMC11199305 DOI: 10.1007/s13318-024-00896-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/27/2024] [Indexed: 05/02/2024]
Abstract
Cytochrome P450 (CYP) enzymes play a central role in the elimination of approximately 80% of all clinically used drugs. Differences in CYP enzyme activity between individuals can contribute to interindividual variability in exposure and, therefore, treatment outcome. In vivo CYP enzyme activity could be determined with phenotyping. Currently, (sub)therapeutic doses are used for in vivo phenotyping, which can lead to side effects. The use of microdoses (100 µg) for in vivo phenotyping for CYP enzymes could overcome the limitations associated with the use of (sub)therapeutic doses of substrates. The aim of this review is to provide a critical overview of the application of microdosing for in vivo phenotyping of CYP enzymes. A literature search was performed to find drug-drug interaction studies of CYP enzyme substrates that used microdoses of the respective substrates. A substrate was deemed sensitive to changes in CYP enzyme activity when the pharmacokinetics of the substrate significantly changed during inhibition and induction of the enzyme. On the basis of the currently available evidence, the use of microdosing for in vivo phenotyping for subtypes CYP1A2, CYP2C9, CYP2D6, and CYP2E1 is not recommended. Microdosing can be used for the in vivo phenotyping of CYP2C19 and CYP3A. The recommended microdose phenotyping test for CYP2C19 is measuring the omeprazole area-under-the-concentration-time curve over 24 h (AUC0-24) after administration of a single 100 µg dose. CYP3A activity could be best determined with a 0.1-75 µg dose of midazolam, and subsequently measuring AUC extrapolated to infinity (AUC∞) or clearance. Moreover, there are two metrics available for midazolam using a limited sampling strategy: AUC over 10 h (AUC0-10) and AUC from 2 to 4 h (AUC2-4).
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Affiliation(s)
- Lisa T van der Heijden
- Department of Pharmacology and Pharmacy, Antoni van Leeuwenhoek/The Netherlands Cancer Institute, Amsterdam, The Netherlands.
- Division of Pharmacology, Antoni van Leeuwenhoek/The Netherlands Cancer Institute, Amsterdam, The Netherlands.
- Department of Clinical Pharmacy, OLVG Hospital, Amsterdam, The Netherlands.
| | - Frans L Opdam
- Department of Medical Oncology, The Netherlands Cancer Institute, Amsterdam, The Netherlands
| | - Jos H Beijnen
- Department of Pharmacology and Pharmacy, Antoni van Leeuwenhoek/The Netherlands Cancer Institute, Amsterdam, The Netherlands
- Division of Pharmacology, Antoni van Leeuwenhoek/The Netherlands Cancer Institute, Amsterdam, The Netherlands
- Division of Pharmaco-Epidemiology and Clinical Pharmacology, Department of Pharmaceutical Sciences, Faculty of Science, Utrecht University, Utrecht, The Netherlands
| | - Alwin D R Huitema
- Department of Pharmacology and Pharmacy, Antoni van Leeuwenhoek/The Netherlands Cancer Institute, Amsterdam, The Netherlands
- Division of Pharmacology, Antoni van Leeuwenhoek/The Netherlands Cancer Institute, Amsterdam, The Netherlands
- Department of Clinical Pharmacy, University Medical Center Utrecht, Utrecht University, Utrecht, The Netherlands
- Department of Pharmacology, Princess Maxima Center, Utrecht, The Netherlands
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Rohr BS, Krohmer E, Foerster KI, Burhenne J, Schulz M, Blank A, Mikus G, Haefeli WE. Time Course of the Interaction Between Oral Short-Term Ritonavir Therapy with Three Factor Xa Inhibitors and the Activity of CYP2D6, CYP2C19, and CYP3A4 in Healthy Volunteers. Clin Pharmacokinet 2024; 63:469-481. [PMID: 38393578 PMCID: PMC11052790 DOI: 10.1007/s40262-024-01350-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/29/2024] [Indexed: 02/25/2024]
Abstract
BACKGROUND We investigated the effect of a 5-day low-dose ritonavir therapy, as it is used in the treatment of COVID-19 with nirmatrelvir/ritonavir, on the pharmacokinetics of three factor Xa inhibitors (FXaI). Concurrently, the time course of the activities of the cytochromes P450 (CYP) 3A4, 2C19, and 2D6 was assessed. METHODS In an open-label, fixed sequence clinical trial, the effect and duration of a 5-day oral ritonavir (100 mg twice daily) treatment on the pharmacokinetics of three oral microdosed FXaI (rivaroxaban 25 µg, apixaban 25 µg, and edoxaban 50 µg) and microdosed probe drugs (midazolam 25 µg, yohimbine 50 µg, and omeprazole 100 µg) was evaluated in eight healthy volunteers. The plasma concentrations of all drugs were quantified using validated liquid chromatography-tandem mass spectrometry (LC-MS/MS) methods and pharmacokinetics were analysed using non-compartmental analyses. RESULTS Ritonavir increased the exposure of apixaban, edoxaban, and rivaroxaban, but to a different extent the observed area under the plasma concentration-time curve (geometric mean ratio 1.29, 1.46, and 1.87, respectively). A strong CYP3A4 inhibition (geometric mean ratio > 10), a moderate CYP2C19 induction 2 days after ritonavir (0.64), and no alteration of CYP2D6 were observed. A CYP3A4 recovery half-life of 2.3 days was determined. CONCLUSION This trial with three microdosed FXaI suggests that at most the rivaroxaban dose should be reduced during short-term ritonavir, and only in patients receiving high maintenance doses. Thorough time series analyses demonstrated differential effects on three different drug-metabolising enzymes over time with immediate profound inhibition of CYP3A4 and only slow recovery after discontinuation. CLINICAL TRIAL REGISTRATION EudraCT number: 2021-006643-39.
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Affiliation(s)
- Brit S Rohr
- Department of Clinical Pharmacology and Pharmacoepidemiology, University of Heidelberg, Medical Faculty of Heidelberg, Heidelberg University Hospital, Im Neuenheimer Feld 410, 69120, Heidelberg, Germany
| | - Evelyn Krohmer
- Department of Clinical Pharmacology and Pharmacoepidemiology, University of Heidelberg, Medical Faculty of Heidelberg, Heidelberg University Hospital, Im Neuenheimer Feld 410, 69120, Heidelberg, Germany
| | - Kathrin I Foerster
- Department of Clinical Pharmacology and Pharmacoepidemiology, University of Heidelberg, Medical Faculty of Heidelberg, Heidelberg University Hospital, Im Neuenheimer Feld 410, 69120, Heidelberg, Germany
| | - Jürgen Burhenne
- Department of Clinical Pharmacology and Pharmacoepidemiology, University of Heidelberg, Medical Faculty of Heidelberg, Heidelberg University Hospital, Im Neuenheimer Feld 410, 69120, Heidelberg, Germany
| | - Martin Schulz
- Drug Commission of German Pharmacists and Institute of Pharmacy, Freie Universität Berlin, Berlin, Germany
| | - Antje Blank
- Department of Clinical Pharmacology and Pharmacoepidemiology, University of Heidelberg, Medical Faculty of Heidelberg, Heidelberg University Hospital, Im Neuenheimer Feld 410, 69120, Heidelberg, Germany
| | - Gerd Mikus
- Department of Clinical Pharmacology and Pharmacoepidemiology, University of Heidelberg, Medical Faculty of Heidelberg, Heidelberg University Hospital, Im Neuenheimer Feld 410, 69120, Heidelberg, Germany
| | - Walter E Haefeli
- Department of Clinical Pharmacology and Pharmacoepidemiology, University of Heidelberg, Medical Faculty of Heidelberg, Heidelberg University Hospital, Im Neuenheimer Feld 410, 69120, Heidelberg, Germany.
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Stoll F, Blank A, Mikus G, Czock D, Weiss J, Meyer-Tönnies MJ, Gümüs KS, Tzvetkov M, Burhenne J, Haefeli WE. Evaluation of Hydroxychloroquine as a Perpetrator on Cytochrome P450 (CYP) 3A and CYP2D6 Activity with Microdosed Probe Drugs in Healthy Volunteers. Eur J Drug Metab Pharmacokinet 2024; 49:101-109. [PMID: 38114885 PMCID: PMC10781839 DOI: 10.1007/s13318-023-00872-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/20/2023] [Indexed: 12/21/2023]
Abstract
BACKGROUND AND OBJECTIVE Although polypharmacy is a particular challenge in daily rheumatological practice, clinical research on the effects of hydroxychloroquine (HCQ), a commonly used drug for patients with rheumatic diseases, is sparse on cytochrome P450 (CYP)-mediated metabolism. We have shown that pre-treatment with pantoprazole does not alter HCQ absorption in healthy volunteers. In this paper, we report the effects of a single 400 mg dose of HCQ on specific CYP3A and CYP2D6 substrates in healthy volunteers. METHODS In the trial, participants were randomized into two groups (HCQ plus a 9-day course of pantoprazole, or HCQ only). As a secondary endpoint, the effects of a single oral dose of HCQ on the exposure of the oral microdosed CYP3A probe drug midazolam (30 μg) and the oral microdosed CYP2D6 probe drug yohimbine (50 μg) were studied in 23 healthy volunteers (EudraCT no. 2020-001470-30, registered 31 March 2020). RESULTS The exposure of the probe drugs after intake of HCQ compared with baseline values was quantified by the partial area under the plasma concentration-time curve 0-6 h after administration (AUC0-6 h) for yohimbine and the partial AUC2-4 h for midazolam. Under HCQ, yohimbine AUC0-6 h was unchanged, independent of CYP2D6 genotypes and pantoprazole exposure. Midazolam AUC2-4 h was 25% higher on the day of HCQ administration than at baseline (p = 0.0007). This significant increase was driven by the pantoprazole subgroup, which showed a 46% elevation of midazolam AUC2-4 h as compared with baseline (p < 0.0001). The ratio of midazolam to 1-OH-midazolam partial AUC2-4 h significantly increased from 3.03 ± 1.59 (baseline) to 3.60 ± 1.56 (HCQ) in the pantoprazole group (p = 0.0026). CONCLUSION In conclusion, we observed an increased midazolam exposure most likely related to pantoprazole.
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Affiliation(s)
- Felicitas Stoll
- Department of Clinical Pharmacology and Pharmacoepidemiology, Medical Faculty Heidelberg/Heidelberg University Hospital, Heidelberg University, Heidelberg, Germany.
| | - Antje Blank
- Department of Clinical Pharmacology and Pharmacoepidemiology, Medical Faculty Heidelberg/Heidelberg University Hospital, Heidelberg University, Heidelberg, Germany
| | - Gerd Mikus
- Department of Clinical Pharmacology and Pharmacoepidemiology, Medical Faculty Heidelberg/Heidelberg University Hospital, Heidelberg University, Heidelberg, Germany
| | - David Czock
- Department of Clinical Pharmacology and Pharmacoepidemiology, Medical Faculty Heidelberg/Heidelberg University Hospital, Heidelberg University, Heidelberg, Germany
| | - Johanna Weiss
- Department of Clinical Pharmacology and Pharmacoepidemiology, Medical Faculty Heidelberg/Heidelberg University Hospital, Heidelberg University, Heidelberg, Germany
| | - Marleen J Meyer-Tönnies
- Department of General Pharmacology, Institute of Pharmacology, Center of Drug Absorption and Transport (C_DAT), University Medicine Greifswald, Greifswald, Germany
| | - Katja S Gümüs
- Department of Clinical Pharmacology and Pharmacoepidemiology, Medical Faculty Heidelberg/Heidelberg University Hospital, Heidelberg University, Heidelberg, Germany
| | - Mladen Tzvetkov
- Department of General Pharmacology, Institute of Pharmacology, Center of Drug Absorption and Transport (C_DAT), University Medicine Greifswald, Greifswald, Germany
| | - Jürgen Burhenne
- Department of Clinical Pharmacology and Pharmacoepidemiology, Medical Faculty Heidelberg/Heidelberg University Hospital, Heidelberg University, Heidelberg, Germany
| | - Walter E Haefeli
- Department of Clinical Pharmacology and Pharmacoepidemiology, Medical Faculty Heidelberg/Heidelberg University Hospital, Heidelberg University, Heidelberg, Germany
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Hermann SA, Mikus G, Chobanyan-Jürgens K, Gorenflo M, Ziesenitz VC. Pharmacokinetics of a microdosed cocktail of three direct oral anticoagulants in children with congenital heart defects: study protocol for a single-centre clinical trial (DOAC-Child). BMJ Paediatr Open 2023; 7:10.1136/bmjpo-2022-001662. [PMID: 36720501 PMCID: PMC9890763 DOI: 10.1136/bmjpo-2022-001662] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/01/2022] [Accepted: 11/20/2022] [Indexed: 02/02/2023] Open
Abstract
INTRODUCTION Direct oral anticoagulants (DOACs) are direct inhibitors of coagulation factor Xa and are frequently used in adults for different indications such as deep vein thrombosis or non-valvular atrial fibrillation. Paediatric patients might benefit as well from DOACs because the simplicity and convenience of their use is likely to decrease physical and psychological stress related to invasive procedures associated with phenprocoumon and heparin therapy. Thus, it is expected that the future use of DOACs will ultimately improve compliance and overall safety of anticoagulant therapies in paediatric populations. To assure safe and effective use the clinical pharmacology and pharmacokinetics (PK) of these drugs need to be evaluated in children. METHODS AND ANALYSIS This study is a single-centre, open-label, clinical trial in a paediatric population with non-cyanotic congenital heart defects. After having obtained informed consent from the parents, each participant will receive a single oral administration of a drinkable solution of a microdose cocktail of three FXa inhibitors consisting of apixaban (12.5 µg), rivaroxaban (12.5 µg), edoxaban (50 µg), plus a microdose of the two probe drugs midazolam (10 µg) and yohimbine (25 µg). Serial blood samples (n=up to 20) will be collected at specified time points before and up to 25 hours after cocktail administration. The primary PK endpoint will be the area under the plasma concentration time curve of apixaban, rivaroxaban and edoxaban. Secondary PK outcomes will be Cmax, tmax, t1/2, Cl/F and Vss/F. Safety and tolerability of the microdose cocktail will be evaluated as well by a collection of adverse events. ETHICS This study has been approved by the responsible Ethics Committee of the Medical Faculty of Heidelberg University. DISSEMINATION Study results will be presented at international scientific meetings and published in peer-reviewed journals. TRIAL REGISTRATION NUMBER EudraCT 2019-001759-38 16, DRKS00021455.
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Affiliation(s)
- Simon A Hermann
- Department of Clinical Pharmacology and Pharmacoepidemiology, UniversitätsKlinikum Heidelberg, Heidelberg, Germany
| | - Gerd Mikus
- Department of Clinical Pharmacology and Pharmacoepidemiology, UniversitätsKlinikum Heidelberg, Heidelberg, Germany
| | - Kristine Chobanyan-Jürgens
- Department of Clinical Pharmacology and Pharmacoepidemiology, UniversitätsKlinikum Heidelberg, Heidelberg, Germany.,Pediatric Clinical-Pharmacological Trial Centre, UniversitätsKlinikum Heidelberg, Heidelberg, Germany
| | - Matthias Gorenflo
- Department of Paediatric and Congenital Cardiology, UniversitätsKlinikum Heidelberg, Heidelberg, Germany
| | - Victoria C Ziesenitz
- Department of Paediatric and Congenital Cardiology, UniversitätsKlinikum Heidelberg, Heidelberg, Germany
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Jabir NR, Firoz CK, Zughaibi TA, Alsaadi MA, Abuzenadah AM, Al-Asmari AI, Alsaieedi A, Ahmed BA, Ramu AK, Tabrez S. A literature perspective on the pharmacological applications of yohimbine. Ann Med 2022; 54:2861-2875. [PMID: 36263866 PMCID: PMC9590431 DOI: 10.1080/07853890.2022.2131330] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Introduction: Phytochemicals have garnered much attention because they are useful in managing several human diseases. Yohimbine is one such phytochemical with significant pharmacological potential and could be exploited for research by medicinal chemists. It is an indole alkaloid obtained from various natural/synthetic sources.Aims and Results: The research on yohimbine started early, and its use as a stimulant and aphrodisiac by humans has been reported for a long time. The pharmacological activity of yohimbine is mediated by the combined action of the central and peripheral nervous systems. It selectively blocks the pre and postsynaptic α2-adrenergic receptors and has a moderate affinity for α1 and α2 subtypes. Yohimbine also binds to other behaviourally relevant monoaminergic receptors in the following order: α-2 NE > 5HT-1A>, 5HT-1B > 1-D > D3 > D2 receptors.Conclusion: The current review highlights some significant findings that contribute to developing yohimbine-based drugs. It also highlights the therapeutic potential of yohimbine against selected human diseases. However, further research is recommended on the pharmacokinetics, molecular mechanisms, and drug safety requirements using well-designed randomized clinical trials to produce yohimbine as a pharmaceutical agent for human use.Key MessagesYohimbine is a natural indole alkaloid with significant pharmacological potential.Humans have used it as a stimulant and aphrodisiac from a relatively early time.It blocks the pre- and postsynaptic α2-adrenergic receptors that could be exploited for managing erectile dysfunction, myocardial dysfunction, inflammatory disorders, and cancer.
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Affiliation(s)
- Nasimudeen R Jabir
- Department of Biochemistry and Biotechnology, Centre for Research and Development, PRIST University, Vallam, Thanjavur, India
| | - Chelapram K Firoz
- Department of Medical Laboratory Technology, MIMS College of Allied Health Sciences, ASTER MIMS Academy, Malappuram, Kerala University of Health Sciences, Kerala, India
| | - Torki A Zughaibi
- Toxicology and Forensic Science Unit, King Fahd Medical Research Center, King Abdulaziz University, Jeddah, Saudi Arabia.,Department of Medical Laboratory Sciences, Faculty of Applied Medical Sciences, King Abdulaziz University, Jeddah, Saudi Arabia
| | - Mohammed Abdullah Alsaadi
- Hematology Research Unit, King Fahd Medical Research Center, King Abdulaziz University, Jeddah, Saudi Arabia
| | - Adel M Abuzenadah
- Toxicology and Forensic Science Unit, King Fahd Medical Research Center, King Abdulaziz University, Jeddah, Saudi Arabia.,Department of Medical Laboratory Sciences, Faculty of Applied Medical Sciences, King Abdulaziz University, Jeddah, Saudi Arabia
| | - Ahmed Ibrahim Al-Asmari
- Toxicology and Forensic Science Unit, King Fahd Medical Research Center, King Abdulaziz University, Jeddah, Saudi Arabia.,Laboratory Department, King Abdul-Aziz Hospital, Ministry of Health, Jeddah, Saudi Arabia
| | - Ahdab Alsaieedi
- Department of Medical Laboratory Sciences, Faculty of Applied Medical Sciences, King Abdulaziz University, Jeddah, Saudi Arabia.,Vaccines and Immunotherapy Unit, King Fahd Medical Research Center, King Abdulaziz University, Jeddah, Saudi Arabia
| | - Bakrudeen Ali Ahmed
- Department of Biochemistry and Biotechnology, Centre for Research and Development, PRIST University, Vallam, Thanjavur, India
| | - Arun Kumar Ramu
- Department of Biochemistry and Biotechnology, Centre for Research and Development, PRIST University, Vallam, Thanjavur, India
| | - Shams Tabrez
- Toxicology and Forensic Science Unit, King Fahd Medical Research Center, King Abdulaziz University, Jeddah, Saudi Arabia.,Department of Medical Laboratory Sciences, Faculty of Applied Medical Sciences, King Abdulaziz University, Jeddah, Saudi Arabia
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An Investigation of O-Demethyl Tramadol/Tramadol Ratio for Cytochrome P450 2D6 Phenotyping: The CYTRAM Study. Pharmaceutics 2022; 14:pharmaceutics14102177. [PMID: 36297612 PMCID: PMC9611900 DOI: 10.3390/pharmaceutics14102177] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2022] [Revised: 09/28/2022] [Accepted: 10/07/2022] [Indexed: 12/03/2022] Open
Abstract
Cytochrome P450 2D6 (CYP2D6) gene polymorphisms influence the exposure to tramadol (T) and its pharmacologically active metabolite, O-demethyl tramadol (O-dT). Tramadol has been considered as a candidate probe drug for CYP2D6 phenotyping. The objective of the CYTRAM study was to investigate the value of plasma O-dT/T ratio for CYP2D6 phenotyping. European adult patients who received IV tramadol after surgery were included. CYP2D6 genotyping was performed and subjects were classified as extensive (EM), intermediate (IM), poor (PM), or ultra-rapid (UM) CYP2D6 metabolizers. Plasma concentrations of tramadol and O-dT were determined at 24 h and 48 h. The relationship between O-dT/T ratio and CYP2D6 phenotype was examined in both a learning and a validation group. Genotype data were obtained in 301 patients, including 23 PM (8%), 117 IM (39%), 154 EM (51%), and 7 UM (2%). Tramadol trough concentrations at 24 h were available in 297 patients. Mean value of O-dT/T ratio was significantly lower in PM than in non-PM individuals (0.061 ± 0.031 versus 0.178 ± 0.09, p < 0.01). However, large overlap was observed in the distributions of O-dT/T ratio between groups. Statistical models based on O-dT/T ratio failed to identify CYP2D6 phenotype with acceptable sensitivity and specificity. Those results suggest that tramadol is not an adequate probe drug for CYP2D6 phenotyping.
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Evaluation of CYP2C19 activity using microdosed oral omeprazole in humans. Eur J Clin Pharmacol 2022; 78:975-987. [PMID: 35238961 PMCID: PMC9107402 DOI: 10.1007/s00228-022-03304-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2021] [Accepted: 02/24/2022] [Indexed: 11/22/2022]
Abstract
Purpose To investigate the suitability of microdosed oral omeprazole for predicting CYP2C19 activity in vivo in combination with simultaneous assessment of CYP3A and CYP2D6 activity using both microdosed midazolam and yohimbine. Methods An open, fixed-sequence study was carried out in 20 healthy participants. Single microdosed (100 µg) and therapeutic (20 mg) doses of omeprazole were evaluated without comedication and after administration of established CYP2C19 perpetrators fluconazole (inhibition) and rifampicin (induction). To prevent degradation of the uncoated omeprazole microdose, sodium bicarbonate buffer was administered. The pharmacokinetics of omeprazole and its 5-hydroxy-metabolite were assessed as well as the pharmacokinetics of midazolam and yohimbine to estimate CYP3A4 and CYP2D6 activity. Results Calculated pharmacokinetic parameters after administration of 100 µg and 20 mg omeprazole in healthy subjects suggest dose proportionality. Omeprazole clearance was significantly decreased by fluconazole from 388 [95% CI: 266–565] to 47.2 [42.8–52.0] mL/min after 20 mg omeprazole and even further after 100 µg omeprazole (29.4 [24.5–35.1] mL/min). Rifampicin increased CYP2C19-mediated omeprazole metabolism. The omeprazole hydroxylation index was significantly related to omeprazole clearance for both doses. Both fluconazole and rifampicin altered CYP3A4 activity whereas no change of CYP2D6 activity was observed at all. Conclusions Microdosed oral omeprazole is suitable to determine CYP2C19 activity, also during enzyme inhibition and induction. However, the administration of sodium bicarbonate buffer also had a small influence on all victim drugs used. Trial registration EudraCT: 2017–004270-34. Supplementary information The online version contains supplementary material available at 10.1007/s00228-022-03304-3.
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CYP2D6 phenotype explains reported yohimbine concentrations in four severe acute intoxications. Arch Toxicol 2021; 95:2867-2870. [PMID: 34027562 PMCID: PMC8298364 DOI: 10.1007/s00204-021-03082-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2021] [Accepted: 05/17/2021] [Indexed: 11/28/2022]
Abstract
The indole alkaloid yohimbine is an alpha-2 receptor antagonist used for its sympathomimetic effects. Several cases of yohimbine intoxication have been reported and the most recent one involved four individuals taking a yohimbine-containing drug powder. All individuals developed severe intoxication symptoms and were admitted to the hospital. Even though all individuals were assumed to have taken the same dose of the drug powder, toxicology analyses revealed yohimbine blood concentrations of 249–5631 ng/mL, amounting to a 22-fold difference. The reason for this high variability remained to be elucidated. We used recently reported knowledge on the metabolism of yohimbine together with state-of-the art nonlinear mixed-effects modelling and simulation and show that a patient’s cytochrome P450 2D6 (CYP2D6) phenotype can explain the large differences observed in the measured concentration after intake of the same yohimbine dose. Our findings can be used both for the identification of safe doses in therapeutic use of yohimbine and for an explanation of individual cases of overdosing.
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Mueller-Schoell A, Michelet R, Klopp-Schulze L, van Dyk M, Mürdter TE, Schwab M, Joerger M, Huisinga W, Mikus G, Kloft C. Computational Treatment Simulations to Assess the Need for Personalized Tamoxifen Dosing in Breast Cancer Patients of Different Biogeographical Groups. Cancers (Basel) 2021; 13:cancers13102432. [PMID: 34069810 PMCID: PMC8157244 DOI: 10.3390/cancers13102432] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2021] [Revised: 05/10/2021] [Accepted: 05/13/2021] [Indexed: 12/24/2022] Open
Abstract
Simple Summary Tamoxifen is a drug often used to treat the most common type of breast cancer. Its metabolite endoxifen is formed by the liver enzyme CYP2D6, whose activity is variable and depends on a patient’s genetic profile. The frequency of CYP2D6 variants with different functional enzymatic activity varies largely between populations. To ensure sufficient efficacy of tamoxifen, a certain target concentration of endoxifen is needed, and 20% of White breast cancer patients have been shown not to reach this target concentration. However, little is known about the risk of not attaining the endoxifen target amongst other ethnic populations. This study investigated the risk for suboptimal endoxifen concentration in nine different biogeographical populations based on their distinct CYP2D6 genetic profile. The variability between the populations was high (up to three-fold), and East Asian breast cancer patients were identified as the population with the highest need for personalized tamoxifen dosing. Abstract Tamoxifen is used worldwide to treat estrogen receptor-positive breast cancer. It is extensively metabolized, and minimum steady-state concentrations of its metabolite endoxifen (CSS,min ENDX) >5.97 ng/mL have been associated with favorable outcome. Endoxifen formation is mediated by the enzyme CYP2D6, and impaired CYP2D6 function has been associated with lower CSS,min ENDX. In the Women’s Healthy Eating and Living (WHEL) study proposing the target concentration, 20% of patients showed subtarget CSS,min ENDX at tamoxifen standard dosing. CYP2D6 allele frequencies vary largely between populations, and as 87% of the patients in the WHEL study were White, little is known about the risk for subtarget CSS,min ENDX in other populations. Applying pharmacokinetic simulations, this study investigated the risk for subtarget CSS,min ENDX at tamoxifen standard dosing and the need for dose individualization in nine different biogeographical groups with distinct CYP2D6 allele frequencies. The high variability in CYP2D6 allele frequencies amongst the biogeographical groups resulted in an up to three-fold difference in the percentages of patients with subtarget CSS,min ENDX. Based on their CYP2D6 allele frequencies, East Asian breast cancer patients were identified as the population for which personalized, model-informed precision dosing would be most beneficial (28% of patients with subtarget CSS,min ENDX).
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Affiliation(s)
- Anna Mueller-Schoell
- Department of Clinical Pharmacy and Biochemistry, Institute of Pharmacy, Freie Universitaet Berlin, 12169 Berlin, Germany; (A.M.-S.); (R.M.); (L.K.-S.); (G.M.)
- Graduate Research Training Program PharMetrX, 12169 Berlin, Germany
| | - Robin Michelet
- Department of Clinical Pharmacy and Biochemistry, Institute of Pharmacy, Freie Universitaet Berlin, 12169 Berlin, Germany; (A.M.-S.); (R.M.); (L.K.-S.); (G.M.)
| | - Lena Klopp-Schulze
- Department of Clinical Pharmacy and Biochemistry, Institute of Pharmacy, Freie Universitaet Berlin, 12169 Berlin, Germany; (A.M.-S.); (R.M.); (L.K.-S.); (G.M.)
| | - Madelé van Dyk
- College of Medicine and Public Health, Flinders University, Adelaide, SA 5042, Australia;
| | - Thomas E. Mürdter
- Dr. Margarete Fischer-Bosch Institute of Clinical Pharmacology, Stuttgart, and University Tübingen, 70376 Tübingen, Germany;
| | - Matthias Schwab
- Dr. Margarete Fischer-Bosch Institute of Clinical Pharmacology, 70376 Stuttgart, Germany;
- German Cancer Consortium (DKTK), Partner Site Tübingen, German Cancer Research, 69120 Heidelberg, Germany
- Departments of Clinical Pharmacology, Pharmacy and Biochemistry, University Tübingen, 72076 Tübingen, Germany
| | - Markus Joerger
- Department of Medical Oncology and Hematology, Cantonal Hospital, 9007 St. Gallen, Switzerland;
| | - Wilhelm Huisinga
- Institute of Mathematics, University of Potsdam, 14476 Potsdam, Germany;
| | - Gerd Mikus
- Department of Clinical Pharmacy and Biochemistry, Institute of Pharmacy, Freie Universitaet Berlin, 12169 Berlin, Germany; (A.M.-S.); (R.M.); (L.K.-S.); (G.M.)
- Department of Clinical Pharmacology and Pharmacoepidemiology, University Hospital Heidelberg, 69120 Heidelberg, Germany
- Department of Clinical Pharmacy, Institute of Pharmacy, University of Bonn, 53113 Bonn, Germany
| | - Charlotte Kloft
- Department of Clinical Pharmacy and Biochemistry, Institute of Pharmacy, Freie Universitaet Berlin, 12169 Berlin, Germany; (A.M.-S.); (R.M.); (L.K.-S.); (G.M.)
- Correspondence:
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