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Kim CS, Sayler AL, Dean H, Ruel NM, Hammond JR. Functional comparison of human and murine equilibrative nucleobase transporter 1. PLoS One 2024; 19:e0311519. [PMID: 39361655 PMCID: PMC11449324 DOI: 10.1371/journal.pone.0311519] [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] [Received: 07/05/2024] [Accepted: 09/19/2024] [Indexed: 10/05/2024] Open
Abstract
6-Mercaptopurine (6-MP) maintenance therapy is the mainstay for various types of leukemia and inflammatory bowel disease. 6-MP is associated with numerous adverse effects including gastrointestinal intolerance, myelotoxicity, and hepatotoxicity. This can lead to therapy discontinuation which is associated with a higher risk of relapse. Drug transporter expression is a known factor contributing to patient variability in drug response and toxicity. We have established that the SLC43A3-encoded equilibrative nucleobase transporter 1 (ENBT1) mediates the transport of 6-MP into human lymphocytes and human embryonic kidney 293 (HEK293) cell lines transfected with SLC43A3. ENBT1 is known to be expressed in the gastrointestinal tract, bone marrow, and the liver. However, the relationship between ENBT1 and 6-MP-associated adverse events, and its pharmacokinetics, is unknown. To validate the use of mouse models (e.g. slc43a3-null mice) for exploring this relationship, we assessed the functional similarities between human and murine ENBT1 using HEK293 cells transfected with the respective SLC43A3/slc43a3 constructs, and the leukemia cell lines MOLT-4 (human) and L1210 (murine). Based on in silico analyses of structural similarities between transporters, we hypothesized that human and murine ENBT1 will have similar 6-MP transport/inhibition kinetics and a similar impact on 6-MP-induced cytotoxicity. We show herein that mslc43a3-encoded mouse ENBT1 transports both [3H]6-MP and [3H]adenine with kinetics similar to those of hSLC43A3-encoded human ENBT1. Both are also similarly distributed in mouse and human tissues. Therefore, data obtained from mouse models where ENBT1 is disrupted or modified may provide clinically relevant insights on its roles in modulating the actions of 6-MP.
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Affiliation(s)
- Chan S. Kim
- Department of Pharmacology, University of Alberta, Edmonton, Alberta, Canada
| | - Aaron L. Sayler
- Department of Pharmacology, University of Alberta, Edmonton, Alberta, Canada
| | - Hannah Dean
- Department of Pharmacology, University of Alberta, Edmonton, Alberta, Canada
| | - Nicholas M. Ruel
- Department of Pharmacology, University of Alberta, Edmonton, Alberta, Canada
| | - James R. Hammond
- Department of Pharmacology, University of Alberta, Edmonton, Alberta, Canada
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2
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Gebhard A, Lilienthal P, Metzler M, Rauh M, Sager S, Schmiegelow K, Toksvang LN, Zierk J. Pharmacokinetic-pharmacodynamic modeling of maintenance therapy for childhood acute lymphoblastic leukemia. Sci Rep 2023; 13:11749. [PMID: 37474565 PMCID: PMC10359452 DOI: 10.1038/s41598-023-38414-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2023] [Accepted: 07/07/2023] [Indexed: 07/22/2023] Open
Abstract
In the treatment of childhood acute lymphoblastic leukemia (ALL), current protocols combine initial high-dose multiagent chemotherapy with prolonged oral therapy with 6-mercaptopurine (6MP) and low-dose methotrexate (MTX) maintenance therapy. Decades of research on ALL treatment have resulted in survival rates of approximately 90%. However, dose-response relationships vary widely between patients and insight into the influencing factors, that would allow for improved personalized treatment management, is insufficient. We use a detailed data set with measurements of thioguanine nucleotides and MTX in red blood cells and absolute neutrophil count (ANC) to develop pharmacokinetic models for 6MP and MTX, as well as a pharmacokinetic-pharmacodynamic (PKPD) model capable of predicting individual ANC levels and thus contributing to the development of personalized treatment strategies. Here, we show that integrating metabolite measurements in red blood cells into the full PKPD model improves results when less data is available, but that model predictions are comparable to those of a fixed pharmacokinetic model when data availability is not limited, providing further evidence of the quality of existing models. With this comprehensive model development leading to dynamics similar to simpler models, we validate the suitability of this model structure and provide a foundation for further exploration of maintenance therapy strategies through simulation and optimization.
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Affiliation(s)
- Anna Gebhard
- MathOpt group, Institute of Mathematical Optimization, Faculty of Mathematics, Otto von Guericke University Magdeburg, Magdeburg, Germany.
| | - Patrick Lilienthal
- MathOpt group, Institute of Mathematical Optimization, Faculty of Mathematics, Otto von Guericke University Magdeburg, Magdeburg, Germany
| | - Markus Metzler
- Department of Pediatrics and Adolescent Medicine, University Hospital Erlangen, Erlangen, Germany
| | - Manfred Rauh
- Department of Pediatrics and Adolescent Medicine, University Hospital Erlangen, Erlangen, Germany
| | - Sebastian Sager
- MathOpt group, Institute of Mathematical Optimization, Faculty of Mathematics, Otto von Guericke University Magdeburg, Magdeburg, Germany
| | - Kjeld Schmiegelow
- Department of Pediatrics and Adolescent Medicine, University Hospital Rigshospitalet, Copenhagen, Denmark
- Institute of Clinical Medicine, Faculty of Medicine, University of Copenhagen, Copenhagen, Denmark
| | - Linea Natalie Toksvang
- Department of Pediatrics and Adolescent Medicine, University Hospital Rigshospitalet, Copenhagen, Denmark
| | - Jakob Zierk
- Department of Pediatrics and Adolescent Medicine, University Hospital Erlangen, Erlangen, Germany
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Ruel NM, Nguyen KH, Kim CS, Andrade LPS, Hammond JR. Impact of SLC43A3/ENBT1 expression and function on 6-mercaptopurine transport and cytotoxicity in human acute lymphoblastic leukemia cells. J Pharmacol Exp Ther 2022; 382:335-345. [PMID: 35798387 DOI: 10.1124/jpet.122.001155] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2022] [Accepted: 06/24/2022] [Indexed: 11/22/2022] Open
Abstract
6-Mercaptopurine (6-MP) is used extensively in the treatment of acute lymphoblastic leukemia (ALL) and inflammatory bowel diseases. Our lab determined previously, using a recombinant HEK293 cell model, that the SLC43A3-encoded equilibrative nucleobase transporter 1 (ENBT1) transports 6-MP into cells and significantly impacts the cytotoxicity of 6-MP in that model. To further investigate the clinical relevance of this finding, we now extend this work to an analysis of the impact of SLC43A3/ENBT1 expression and function on 6-MP uptake and cytotoxicity in leukemic lymphoblasts, the therapeutic target of 6-MP in ALL. A panel of ALL cell lines was assessed for SLC43A3/ENBT1 expression, ENBT1 function, and sensitivity to 6-MP. There was a significant difference in SLC43A3 expression among the cell lines that positively correlated with the rate of ENBT1-mediated 6-MP uptake. Cells with the lowest expression of SLC43A3 (SUP-B15: Vmax - 22 {plus minus} 5 pmol/µl/s) were also significantly less sensitive to 6-MP induced cytotoxicity than were the highest expressing cells (ALL-1: Vmax - 69 {plus minus} 10 pmol/µl/s). Furthermore, knockdown of ENBT1 using shRNAi in RS4;11 cells caused a significant decrease in ENBT1-mediated 6-MP uptake (Vmax: RS4;11 - 40 {plus minus} 4 pmol/µl/s; RS4;11 shRNAi - 26 {plus minus} 3 pmol/µl/s) and 6-MP cytotoxicity (EC50: RS4;11: 0.58 {plus minus} 0.05 µM; RS4;11 shRNAi: 1.44 {plus minus} 0.59 µM). This study showed that ENBT1 is a major contributor to 6-MP uptake in leukemia cell lines, and may prove to be a biomarker for the therapeutic efficacy of 6-MP in patients with ALL. Significance Statement This study shows that ENBT1 is responsible for the transport of 6-MP into leukemia cells and that its level of expression can impact the cytotoxicity of 6-MP. Further studies are warranted to investigate the therapeutic implications in patient populations.
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Affiliation(s)
| | | | - Chan S Kim
- Pharmacology, University of Alberta, Canada
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Pranzatelli MR, Tate ED, Allison TJ. 6-Mercaptopurine modifies cerebrospinal fluid T cell abnormalities in paediatric opsoclonus-myoclonus as steroid sparer. Clin Exp Immunol 2017; 190:217-225. [PMID: 28710878 DOI: 10.1111/cei.13015] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/12/2017] [Indexed: 11/26/2022] Open
Abstract
The purpose of this study was to evaluate the capacity of 6-mercaptopurine (6-MP), a known immunosuppressant, to normalize cerebrospinal fluid (CSF) lymphocyte frequencies in opsoclonus-myoclonus syndrome (OMS) and function as a steroid sparer. CSF and blood lymphocytes were immunophenotyped in 11 children with OMS (without CSF B cell expansion) using a comprehensive panel of cell surface adhesion, activation and maturation markers by flow cytometry, and referenced to 18 paediatric controls. Drug metabolites, lymphocyte counts and liver function tests were used clinically to monitoring therapeutic range and toxicity. In CSF, adjunctive oral 6-MP was associated with a 21% increase in the low percentage of CD4+ T cells in OMS, restoring the CD4/CD8 ratio. The percentage of CD4+ T cells that were interferon (IFN)-γ+ was reduced by 66%, shifting the cytokine balance away from T helper type 1 (Th1) (proinflammatory) predominance. The percentage of natural killer (NK) cells decreased significantly in CSF (-32%) and blood (-67 to -82%). Low blood absolute lymphocyte count was more predictive of improvement in CSF lymphocyte proportions (correlated with % CD4+ T cells) than the 6-thioguanine level (no correlation). 6-MP was difficult to titrate: 50% achieved the target absolute lymphocyte count (< 1·5 K/mm); 20%, the 'therapeutic' 6-thioguanine level; and 40% the non-toxic 6-methylmercaptopurine level. Side effects and transaminase elevation were mild and reversible. Clinical steroid-sparing properties and lowered relapse frequency were demonstrated. 6-MP displayed unique pharmacodynamic properties that may be useful in OMS and other autoimmune disorders. Its steroid sparer capacity is limited to children in whom the therapeutic window can be reached without limiting pharmacokinetic factors or side effects.
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Affiliation(s)
- M R Pranzatelli
- National Pediatric Neuroinflammation Organization, Inc., the National Pediatric Myoclonus Center, Orlando, FL, USA
| | - E D Tate
- National Pediatric Neuroinflammation Organization, Inc., the National Pediatric Myoclonus Center, Orlando, FL, USA
| | - T J Allison
- National Pediatric Neuroinflammation Organization, Inc., the National Pediatric Myoclonus Center, Orlando, FL, USA
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Abstract
Cancer treatment is becoming more and more individually based as a result of the large inter-individual differences that exist in treatment outcome and toxicity when patients are treated using population-based drug doses. Polymorphisms in genes encoding drug-metabolizing enzymes and transporters can significantly influence uptake, metabolism, and elimination of anticancer drugs. As a result, the altered pharmacokinetics can greatly influence drug efficacy and toxicity. Pharmacogenetic screening and/or drug-specific phenotyping of cancer patients eligible for treatment with chemotherapeutic drugs, prior to the start of anticancer treatment, can identify patients with tumors that are likely to be responsive or resistant to the proposed drugs. Similarly, the identification of patients with an increased risk of developing toxicity would allow either dose adaptation or the application of other targeted therapies. This review focuses on the role of genetic polymorphisms significantly altering the pharmacokinetics of anticancer drugs. Polymorphisms in DPYD, TPMT, and UGT1A1 have been described that have a major impact on the pharmacokinetics of 5-fluorouracil, mercaptopurine, and irinotecan, respectively. For other drugs, however, the association of polymorphisms with pharmacokinetics is less clear. To date, the influence of genetic variations on the pharmacokinetics of the increasingly used monoclonal antibodies has hardly been investigated. Some studies indicate that genes encoding the Fcγ-receptor family are of interest, but more research is needed to establish if screening before the start of therapy is beneficial. Considering the profound impact of polymorphisms in drug transporters and drug-metabolizing enzymes on the pharmacokinetics of chemotherapeutic drugs and hence, their toxicity and efficacy, pharmacogenetic and pharmacokinetic profiling should become the standard of care.
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Affiliation(s)
| | | | - André B P van Kuilenburg
- Department of Clinical Chemistry, Laboratory Genetic Metabolic Diseases, Academic Medical Center, University of Amsterdam, Emma Children's Hospital, F0-220, Meibergdreef 9, 1105 AZ, Amsterdam, The Netherlands.
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Ogungbenro K, Aarons L. Physiologically based pharmacokinetic model for 6-mercpatopurine: exploring the role of genetic polymorphism in TPMT enzyme activity. Br J Clin Pharmacol 2015; 80:86-100. [PMID: 25614061 PMCID: PMC4500328 DOI: 10.1111/bcp.12588] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2014] [Revised: 12/12/2014] [Accepted: 01/05/2015] [Indexed: 12/18/2022] Open
Abstract
AIMS To extend the physiologically based pharmacokinetic (PBPK) model developed for 6-mercaptopurine to account for intracellular metabolism and to explore the role of genetic polymorphism in the TPMT enzyme on the pharmacokinetics of 6-mercaptopurine. METHODS The developed PBPK model was extended for 6-mercaptopurine to account for intracellular metabolism and genetic polymorphism in TPMT activity. System and drug specific parameters were obtained from the literature or estimated using plasma or intracellular red blood cell concentrations of 6-mercaptopurine and its metabolites. Age-dependent changes in parameters were implemented for scaling, and variability was also introduced for simulation. The model was validated using published data. RESULTS The model was extended successfully. Parameter estimation and model predictions were satisfactory. Prediction of intracellular red blood cell concentrations of 6-thioguanine nucleotide for different TPMT phenotypes (in a clinical study that compared conventional and individualized dosing) showed results that were consistent with observed values and reported incidence of haematopoietic toxicity. Following conventional dosing, the predicted mean concentrations for homozygous and heterozygous variants, respectively, were about 10 times and two times the levels for wild-type. However, following individualized dosing, the mean concentration was around the same level for the three phenotypes despite different doses. CONCLUSIONS The developed PBPK model has been extended for 6-mercaptopurine and can be used to predict plasma 6-mercaptopurine and tissue concentration of 6-mercaptopurine, 6-thioguanine nucleotide and 6-methylmercaptopurine ribonucleotide in adults and children. Predictions of reported data from clinical studies showed satisfactory results. The model may help to improve 6-mercaptopurine dosing, achieve better clinical outcome and reduce toxicity.
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Affiliation(s)
- Kayode Ogungbenro
- Centre for Applied Pharmacokinetics Research, Manchester Pharmacy School, The University of ManchesterOxford Road, Manchester, M13 9PT, United Kingdom
| | - Leon Aarons
- Centre for Applied Pharmacokinetics Research, Manchester Pharmacy School, The University of ManchesterOxford Road, Manchester, M13 9PT, United Kingdom
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Physiologically based pharmacokinetic modelling of methotrexate and 6-mercaptopurine in adults and children. Part 2: 6-mercaptopurine and its interaction with methotrexate. J Pharmacokinet Pharmacodyn 2014; 41:173-85. [DOI: 10.1007/s10928-014-9355-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2013] [Accepted: 03/06/2014] [Indexed: 10/25/2022]
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Skoglund KA, Söderhäll S, Beck O, Peterson C, Wennberg M, Hayder S, Björk O. Plasma and urine levels of methotrexate and 7-hydroxymethotrexate in children with ALL during maintenance therapy with weekly oral methotrexate. MEDICAL AND PEDIATRIC ONCOLOGY 1994; 22:187-93. [PMID: 8272008 DOI: 10.1002/mpo.2950220307] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
A new high-performance liquid chromatographic assay was used to determine methotrexate (MTX) and its main metabolite, 7-hydroxymethotrexate (7-OH-MTX), in the plasma (n = 17) and urine (n = 14) of children (age 3-12 years) on maintenance therapy for acute lymphocytic leukemia (n = 14) or non-Hodgkin's lymphoma (n = 3). Each child received oral doses of weekly MTX (4.0-29 mg/m2) and daily 6-mercaptopurine (40-111 mg/m2). Plasma samples were collected daily from two children during the 1-week dose interval. A limited sampling strategy was designed, whereby 2 days of blood sampling were used in the other 15 patients. Morning urine samples were collected daily for 1 week following MTX intake from 14 of the children. MTX was detectable in all plasma and urine samples for the entire dose interval. The main metabolite, 7-OH-MTX, could be detected in plasma and urine from all patients on the first day after dose intake but only in a few patients during the whole dose interval. Interpatient variability of MTX and 7-OH-MTX levels was high at all points during the week. Significant correlation were found between the urinary MTX levels on days 2 and 7 and plasma MTX levels on day 2 after intake. No significant correlation was found between drug levels in plasma or urine and liver function tests in the children showing signs of mild liver injury. This assay provides a tool for further studies on the role of pharmacokinetics for the clinical effects of weekly oral low-dose MTX given alone or in combination with 6-mercaptopurine.
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Affiliation(s)
- K A Skoglund
- Department of Pediatric Oncology, Karolinska Hospital, Stockholm, Sweden
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9
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Lafolie P, Hayder S, Björk O, Peterson C. Intraindividual variation in 6-mercaptopurine pharmacokinetics during oral maintenance therapy of children with acute lymphoblastic leukaemia. Eur J Clin Pharmacol 1991; 40:599-601. [PMID: 1884741 DOI: 10.1007/bf00279977] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Intraindividual variation in 6-mercaptopurine (6-MP) kinetics has been little studied. It has now been examined in 18 children with acute lymphoblastic leukaemia (ALL). On 2 to 4 occasions in each patient drug concentrations in plasma and red cells were followed for 4 h after administration by means of HPLC. The mean individual coefficient of variation (C.V.) in AUC was 57.9% and it was not related to dose or concentration. The variation was the same in plasma and in red cells. It is concluded that regular monitoring of 6-mercaptopurine concentration would identify periods when a patient deviates strongly from the mean range. Both undertreatment and concentration-dependent toxicity could then be corrected.
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Affiliation(s)
- P Lafolie
- Department of Clinical Pharmacology, Karolinska Hospital, Stockholm, Sweden
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Lafolie P, Björk O, Hayder S, Ahström L, Peterson C. Variability of 6-mercaptopurine pharmacokinetics during oral maintenance therapy of children with acute leukemia. MEDICAL ONCOLOGY AND TUMOR PHARMACOTHERAPY 1989; 6:259-65. [PMID: 2615529 DOI: 10.1007/bf02985158] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The effects of some environmental and genetic factors on the inter- and intraindividual variations of 6-mercaptopurine (6-MP) pharmacokinetics were studied in children on oral remission maintenance therapy for acute lymphoblastic leukemia or non-Hodgkin's lymphoma. Blood samples were obtained 0-4 h after drug intake. 6-MP concentrations were determined in plasma and in erythrocyte concentrates. The influence of food on the pharmacokinetics was examined in a prospective study of 15 children. Each child was examined four times, twice in the fasted state and twice after intake of a standardized, milky, breakfast. There were pronounced inter- and intraindividual variations. Food intake seemed to reduce these variations but there were no significant changes in peak concentrations and area under the plasma concentration vs time curves (AUC) between the fasted and fed states. Food intake reduced the time to peak concentration both in plasma, from 1.8 h to 1.1 h (P less than 0.01) and in red blood cells, from 1.8 h to 1.3 h (P less than 0.01). Retrospective subdivision of the patients indicated a tendency for different pharmacokinetic patterns according to dose; five out of seven patients receiving greater than 70 mg m-2 had a higher AUC in the fasting state, while five out of eight patients receiving less than 70 mg m-2 had a higher AUC in the fed state. The cytochrome P-450-dependent hydroxylation capacity was evaluated with debrisoquine but no correlation was found to the pharmacokinetics of 6-MP.
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Affiliation(s)
- P Lafolie
- Department of Clinical Pharmacology, Karolinska Hospital, Stockholm, Sweden
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Lönnerholm G, Kreuger A, Lindström B, Myrdal U. Oral mercaptopurine in childhood leukemia: influence of food intake on bioavailability. Pediatr Hematol Oncol 1989; 6:105-12. [PMID: 2702064 DOI: 10.3109/08880018909034276] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Plasma concentrations of 6-mercaptopurine (6-MP) were determined by gas chromatography-mass spectrometry. Ten children (nine with acute lymphatic leukemia) were studied on 2 consecutive days after oral intake of 6-MP. On one day the drug was administered in the fasting state and on the other (in random order) together with breakfast. The peak plasma concentrations of 6-MP after the dose intake with breakfast in percent of that in the fasting state (meal in % of fasting for each individual) varied between 33 and 181% (mean 111), and the area under the plasma concentration-time curve varied between 47 and 186% (mean 103). Thus, there were considerable variations among patients, but, for the group as a whole, there were no statistically significant differences between the two experimental conditions. This study cannot therefore form the basis for a recommendation as to whether 6-MP should be administered on an empty stomach or together with food.
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Affiliation(s)
- G Lönnerholm
- Department of Pediatrics, Uppsala University, Akademiska Sjukhuset, Sweden
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