- Written by Ethan Abbott
An article in the New York Times reported that athletes with Nike’s “Oregon Project have allegedly been using infusions of L-carnitine to enhance their performance during long distance running events. What is L-carnitine and what are its therapeutic uses in emergency medicine?
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Carnitine (the L-isomer is only found endogenously) functions in the metabolism of fatty acids and mitochondrial energy production. It is a water soluble, amino-acid derivative produced in the kidneys and the liver. 75% of carnitine comes from meat and dairy products in the diet. Per the attached reference: “it facilitates fatty acyl group transport into mitochondria and it regulates the mitochondrial ratio of acyl-CoA to free CoA.” Most carnitine is stored in skeletal muscle, but is also found in the myocardium, liver, and adrenal glands.
The drug form of L-carnitine is available in oral and parenteral forms, but bioavailability is limited in the oral form, so parenteral administration is preferred. Outside of the emergency department L-carnitine has been used to treat “senile dementia, inborn errors of metabolism, HIV infection, tuberculosis, zidovudine-induced mitochondrial myopathies, pediatric cardiomyopathies, renal failure on hemodialysis, anemia, and has been included in baby foods and milk.”
In the emergency department, L-carnitine can be used in the treatment of intentional or accidental overdose of valproic acid (VPA). VPA depletes stores of carnitine through several different pathways (see reference) and this can occur during high dose or long-term therapy. In VPA toxicity, several complications can occur “including fatal hemorrhagic pancreatitis, bone marrow suppression, hepatotoxicity, and hyperammonemic encephalopathy” (although it can also be mild and self-limiting per article).
Reference: Philippe E.R. Lheureux & Philippe Hantson (2009) Carnitine in the treatment of valproic acid-induced toxicity, Clinical Toxicology, 47:2, 101-111