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Pharmacokinetics of L-carnitine
Allan M Evans1, Gianfranco Fornasini
1Centre for Pharmaceutical Research, School of Pharmaceutical, Molecular and Biomedical Sciences, University of South Australia, Adelaide, South Australia, Australia. allan.evans@unisa.edu.au
Clinical Pharmacokinetics
|August 12, 2003
Summary
L-Carnitine is crucial for fatty acid transport and energy production. Supplemental L-carnitine (LC) has lower bioavailability than dietary sources, with renal excretion being the primary elimination route.
Area of Science:
- Biochemistry
- Pharmacology
- Physiology
Background:
- L-Carnitine facilitates fatty acid transport into mitochondria for beta-oxidation.
- Endogenous L-carnitine levels are maintained by diet, biosynthesis, and renal reabsorption.
- Carrier-mediated transport ensures high tissue concentrations for tissues reliant on fatty acid oxidation.
Purpose of the Study:
- To elucidate the pharmacokinetic properties of L-Carnitine.
- To understand L-Carnitine absorption, distribution, and elimination in humans.
- To investigate L-Carnitine handling in carnitine deficiency and end-stage renal disease.
Main Methods:
- Pharmacokinetic analysis of L-Carnitine absorption, distribution, and excretion.
- Assessment of L-Carnitine bioavailability after oral and intravenous administration.
- Evaluation of renal tubular reabsorption and clearance mechanisms.
Main Results:
- Oral L-Carnitine bioavailability is low (5-18%) compared to dietary sources (up to 75%).
- L-Carnitine distributes into extracellular fluid, with slow equilibration into muscle tissue.
- Renal excretion is the primary elimination route, with extensive tubular reabsorption (98-99%) below a threshold concentration.
Conclusions:
- Pharmacological doses of L-Carnitine are absorbed less efficiently than dietary intake.
- Altered renal handling and muscle transport are implicated in carnitine deficiency disorders.
- Dialysis patients may experience secondary carnitine deficiency due to L-Carnitine loss during hemodialysis.