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Open Access

Metabolism of (R)-[11C]verapamil in epilepsy patients

  • Aiman Abrahim1, 5,
  • Gert Luurtsema6,
  • Martin Bauer1,
  • Rudolf Karch2,
  • Christoph Baumgartner3,
  • Kurt Kletter4,
  • Markus Müller1 and
  • Oliver Langer1, 5Email author
BMC Pharmacology20077(Suppl 2):A23

https://doi.org/10.1186/1471-2210-7-S2-A23

Published: 14 November 2007

Introduction

(R)-[11C]Verapamil (VPM) is a new positron emission tomography (PET) tracer to measure P-glycoprotein (P-gp)-mediated transport at the blood-brain barrier (BBB). Owing to the lack of a suitable reference region in brain that is devoid of P-gp, a metabolite-corrected arterial input function is required for quantitative analysis of VPM PET data [1]. The aim of this study was to compare metabolism of VPM in epilepsy patients and healthy volunteers.

Methods

Selected arterial blood samples from 9 patients, who underwent VPM PET, were analyzed for radiolabeled metabolites by a previously described combined solid-phase extraction/HPLC assay [2].

Results

VPM metabolism was significantly faster in patients as compared to healthy volunteers [1] (unchanged VPM at 60 min after injection: 26.1 ± 6.4 vs. 49.0 ± 13.4%, p < 0.05, t-test).

Conclusion

Faster metabolism of VPM in epilepsy patients may be caused by CyP450 enzyme induction by antiepileptic drugs. Based on these data caution is warranted when using an averaged arterial input function derived from healthy volunteers for the analysis of patient data. As radiolabeled metabolites of VPM are known to cross the BBB [1], different kinetic modeling parameters obtained in patients and healthy volunteers might be at least partly attributed to different rates of tracer metabolism rather than to differences in cerebral P-gp activity.

Authors’ Affiliations

(1)
Department of Clinical Pharmacology, Medical University of Vienna
(2)
Department of Medical Computer Sciences, Medical University of Vienna
(3)
Department of Neurology, Medical University of Vienna
(4)
Department of Nuclear Medicine, Medical University of Vienna
(5)
Department of Radiopharmaceuticals, ARC GmbH
(6)
Department of Nuclear Medicine and PET Research, VU University Medical Center

References

  1. Lubberink M, Luurtsema G, van Berckel BN, Boellaard R, Toornvliet R, Windhorst AD, Franssen EJ, Lammertsma AA: Evaluation of tracer kinetic models for quantification of P-glycoprotein function using (R)-[11C]verapamil and PET. J Cereb Blood Flow Metab. 2007, 27: 424-433. 10.1038/sj.jcbfm.9600349.View ArticlePubMedGoogle Scholar
  2. Luurtsema G, Molthoff CF, Schuit RC, Windhorst AD, Lammertsma AA, Franssen EJ: Evaluation of (R)-[11C]verapamil as PET tracer of P-glycoprotein function in the blood-brain barrier: kinetics and metabolism in the rat. Nucl Med Biol. 2005, 32: 87-93. 10.1016/j.nucmedbio.2004.06.007.View ArticlePubMedGoogle Scholar

Copyright

© Abrahim et al; licensee BioMed Central Ltd. 2007

This article is published under license to BioMed Central Ltd.

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