NDT Advance Access originally published online on November 11, 2005
Nephrology Dialysis Transplantation 2006 21(2):450-458; doi:10.1093/ndt/gfi257
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© The Author [2005]. Published by Oxford University Press on behalf of ERA-EDTA. All rights reserved. For Permissions, please email: journals.permissions@oxfordjournals.org
Original Articles: Dialysis and Transplantation
Effect of L-carnitine on the kinetics of carnitine, acylcarnitines and butyrobetaine in long-term haemodialysis
1 Division of Clinical Pharmacology and Toxicology and Department of Research and 2 Division of Nephrology and Transplantation Medicine, University Hospital, Basel, Switzerland
Correspondence and offprint requests to: Stephan Krähenbühl, Division of Clinical Pharmacology and Toxicology, University Hospital, CH-4031 Basel, Switzerland. Email: kraehenbuehl{at}uhbs.ch
Background. The current study was performed to investigate the kinetics of carnitine, individual acylcarnitines and butyrobetaine in patients on haemodialysis.
Methods. Eight stable long-term haemodialysis patients were studied under basal conditions (no carnitine supplementation) and 3 weeks after intravenous supplementation with L-carnitine (10 or 20 mg/kg body weight) after each haemodialysis session. The kinetic studies included serial determinations of carnitine and metabolites just before, during or between haemodialysis sessions. Analysis was performed by liquid chromatography–tandem mass spectrometry.
Results. Before haemodialysis, the plasma concentrations were (µmol/l) 15.1±0.6 (mean±SEM) for carnitine, 5.9±0.7 for acetylcarnitine, 0.66±0.04 for propionylcarnitine and 0.98±0.08 for butyrobetaine (basal conditions) or 142±23 for carnitine, 69±12 for acetylcarnitine, 6.0±1.1 for propionylcarnitine and 2.6±0.3 for butyrobetaine (carnitine 20 mg/kg). During haemodialysis, the plasma concentrations dropped by 
80% for all compounds determined, with extraction coefficients ranging from 0.65 to 0.86. In patients supplemented with 20 mg/kg carnitine, the amount of carnitine removed by haemodialysis equalled 42% of the dose administered, consisting of 2.08 mmol carnitine, 1.03 mmol acetylcarnitine and 0.051 mmol propionylcarnitine. Between the haemodialysis sessions, carnitine, acylcarnitines and butyrobetaine reached apparent steady-state concentrations within 1 day both under basal conditions and after supplementation.
Conclusions. Patients on haemodialysis have reduced carnitine, acylcarnitine and butyrobetaine plasma levels, which can be increased by supplementing carnitine. Propionylcarnitine, an important constituent of the acylcarnitine pool, can be removed by haemodialysis. Removal of potentially toxic acyl-groups may represent a mechanism for a beneficial effect of carnitine in these patients.
Keywords: acylcarnitines; butyrobetaine; carnitine; haemodialysis; liquid chromatography–tandem mass spectrometry
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