|Systematic (IUPAC) name|
|AHFS/Drugs.com||International Drug Names|
|Biological half-life||4.2 hours|
|ATC code||N06BX12 (WHO)|
|(what is this?)|
Acetyl-L-carnitine, ALCAR or ALC, is an acetylated form of L-carnitine. It is naturally produced by the body, although it is often taken as a dietary supplement. Acetylcarnitine is broken down in the blood by plasma esterases to carnitine which is used by the body to transport fatty acids into the mitochondria for breakdown.
Biochemical production and action
ALCAR is an acetylated derivative of L-carnitine. During strenuous exercise, a large portion of L-carnitine and unused acetyl-CoA are converted to ALCAR and CoA inside mitochondria by carnitine O-acetyltransferase. The ALCAR is transported outside the mitochondria where it converts back to the two constituents. The L-carnitine is cycled back into the mitochondria with acyl groups to facilitate fatty acid utilization, but excess acetyl-CoA may block it. Excess acetyl-CoA causes more carbohydrates to be used for energy at the expense of fatty acids. This occurs by different mechanisms inside and outside the mitochondria. ALCAR transport decreases acetyl-CoA inside the mitochondria, but increases it outside. Glucose metabolism in diabetics improves with administration of either ALCAR or L-carnitine. ALCAR decreases glucose consumption in favor of fat oxidation in non-diabetics. A portion of L-carnitine is converted to ALCAR after ingestion in humans.
Absorption compared to L-carnitine
It has been claimed ALCAR is superior to L-carnitine in terms of bioavailability. Both use the same mechanism for intestinal absorption that improves with sodium. One study shows ALCAR has a lower blood concentration in humans after ingestion possibly because ALCAR is hydrolyzed more in blood.
Early research which seemed to suggest acetylcarnitine had potential as a treatment for dementia were not strongly substantiated by later research, and the substance is not routinely used for this purpose. Combinations with other nutrients, however, have shown better results and are currently under investigation. ALCAR may also have some neuroprotective benefit in the treatment of Parkinson's disease, but further research is required.
It has been suggested that ALCAR may have potential as a drug for treating peripheral neuropathic pain. One way through which ALCAR may accomplish this is by helping regenerate injured or stunted nerves  via the release of nerve growth factor.
A single case study published in the March 2015 issue of the Journal of the American Academy of Audiology came to the conclusion that it may be a "valuable pharmacological option in the treatment of tinnitus."
It has been shown that ALCAR interferes with thyroid function by inhibiting triiodothyronine (T3) and thyroxine (T4) from entering the cell nuclei. Therefore, it has some potential in the treatment of hyperthyroidism. Conversely, people with low to normal thyroid function should use it cautiously as large doses could precipitate a drop in thyroid hormones thus leading to fatigue and mental sluggishness (the opposite of what is usually sought after by starting ALCAR supplementation).
A note ought to be made about ALCAR's purported relationship to seizures. People with epileptic disorders/vulnerability are advised, on product monographs and pharmacy databases, to avoid carnitine and its derivatives as it is claimed to promote epileptic discharges. It now appears that this advice has been misguided. According to a systematic review of people with epilepsy treated with valproic acid, these claims are unsubstantiated both in the scientific literature and in clinical practice and may have done more harm than good. This is unfortunate as many people with epilepsy actually have decreased levels of carnitine (especially those under valproate treatment) and might need to supplement with this substance in order to avoid troubling side effects (e.g., hepatotoxicity, hyperammonemic encephalopathy). The exact reason for these cautionary notes against carnitine is not known. One possibility is that a well-intended, but ultimately false, disclaimer has propagated uncontrollably throughout pharmacy texts and electronic databases worldwide. Another possibility is that some of the side effects of ALCAR (e.g., overstimulation, dizziness, headache, nausea) may mimic, and thus be mistaken for, a mild seizure.
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