Acetyl-L-Carnitine is the acetyl ester of L-carnitine.
It occurs naturally in animal products. Chemically, acetyl-L-carnitine
is known as beta-acetoxy-gamma-N, N, N-trimethylaminobutyrate and is represented
by the following chemical structure:
Acetyl-L-carnitine is also known as acetyl-carnitine,
L-acetycarnitine, acetylcarnitine, acetyl levocarnitine, ALC and ALCAR.
Acetyl-L-carnitine is a delivery form for both L-carnitine
and acetyl groups.
ACTIONS AND PHARMACOLOGY
Supplemental acetyl-L-carnitine may have neuroprotective
activity. In addition, it, like L-carnitine, may have cardioprotective
activity and may beneficially affect cardiac function. It may enhance sperm
motiliy. Acetyl-L-carnitine may also have cytoprotective, antioxidant and
MECHANISM OF ACTION
Acetyl-L-carnitine is a delivery form for L-carnitine
and acetyl groups. The functions of L-carnitine include transport of long-chain
fatty acids across the mitochondrial membranes into the mitochondria (wherein
their metabolism produces bioenergy) and transport of small-chain and medium-chain
fatty acids out of the mitochondria in order to, among other things, maintain
normal coenzyme A levels in these organelles. It may also have antioxidant
The acetyl component of acetyl-L-carnitine provides
for the formation of the neurotransmitter acetylcholine. Abnormal acetylcholine
metabolism in the brain, leading to acetylcholine deficits in certain brain
regions, is thought to be associated with age-related dementias, including
Acetyl-L-carnitine has been found to decrease glycation
of lens proteins in vitro. It is thought to do so by acetylating certain
lens proteins called crystallins. In so doing it protects them from glycation-mediated
Many biochemical changes occur during the aging process.
These include decreased cardiolipin synthesis in the heart and impaired
mitochondrial function. Cardiolipin is a key phospholipid necessary for
mitochondrial transport processes in the heart. Mitochondria are vital
for the production of cellular energy. Experiments in aged rats have shown
that acetyl-L-carnitine supplementation leads to improved mitochondrial
function and increased cardiolipin production.
Acetyl-L-carnitine serves as a readily accessible
energy pool for use in both activation of respiration and motility in human
The pharmacokinetics of acetyl-L-carnitine are similar
to L-carnitine (see L-carnitine). There is speculation that it is better
absorbed than L-carnitine, but this has not yet been established.
INDICATIONS AND USAGE
Acetyl-L-carnitine has recently demonstrated some
efficacy as a possible neuroprotective agent and may be indicated for use
in strokes, Alzheimer's disease, Down's syndrome and for the management
of various neuropathies. It may also have anti-aging properties. Research
regarding acetyl-L-carnitine's possible beneficial effect on sperm motility
is early-stage but promising.
Several studies have now demonstrated some positive
effects of acetyl-L-carnitine supplementation in Alzheimer's patients especially
with regard to tasks involving attention and concentration. In a double-blind,
parallel design, placebo-controlled pilot study of 30 patients whose mild-to-moderate
dementias were believed to be symptoms of Alzheimer's disease, there were
significant, positive results as measured by some of the neuropsychological
tests used in the study.
In another early double-blind, placebo-controlled
study of 130 patients with clinical diagnoses of Alzheimer's disease, a
slower rate of deterioration was observed in 13 of 14 outcome measures
at the end of this one-year study. Some of these measures reached statistical
significance, including measures of logical intelligence, long-term verbal
memory and selective attention.
More recent studies continue to show beneficial effects
in Alzheimer's disease. Younger patients seem to benefit most.
It has been suggested that cognitive function may
be improved in subjects with Alzheimer's disease by acetyl-L-carnitine's
hypothesized ability to inhibit apoptosis of cerebral nerve cells.
Significant improvement in visual memory and attention
in Down's syndrome subjects treated with acetyl-L-carnitine has also been
reported. These researchers hypothesized that acetyl-L-carnitine's positive
actions in both Alzheimer's disease and Down's syndrome result from its
direct and indirect cholinomimetic effects.
There is also preliminary evidence that acetyl-L-carnitine
can slow mental decline in the elderly who are not afflicted with dementias.
Neuroprotective effects of acetyl-L-carnitine have
been reported after stroke in both animal models and in humans. Cerebral
blood flow reportedly improves in acetyl-L-carnitine treated subjects with
Peripheral nerve function has been improved with the
use of acetyl-L-carnitine in experimental diabetes. There is also early
clinical evidence that acetyl-L-carnitine may be helpful in various peripheral
neuropathies, and it has been suggested that this supplement might be helpful
in alleviating the neurotoxicity associated with the nucleoside analogues
used in the treatment of AIDS. This latter hypothesis has yet to be tested.
There is some evidence in animal work that acetyl-L-carnitine
might have anti-aging effects. Mitochondrial function and ambulatory activity
were assessed in a study of old rats fed acetyl-L-carnitine. Ambulatory
activity was significantly increased in the old rats, and an examination
of liver cells in the treated animals showed a significant reversal of
age-associated decline of mitochondrial membrane potential. Cardiolipin,
which declines with age, was significantly restored.
Finally, acetyl-L-carnitine has been reported to increase
sperm motility in vitro, and in one human trial, 4 grams daily of this
substance given to 20 oligoasthenospermic men, produced increased progressive
sperm motility which was associated with a greater number of pregnancies.
CONTRAINDICATIONS,PRECAUTIONS, ADVERSE REACTIONS
Because of lack of long-term safety studies, acetyl-L-carnitine
is not advised for pregnant women or nursing mothers. Those with seizure
disorders should only use acetyl-L-carnitine under medical advisement and
Mild gastrointestinal symptoms may occur in those taking acetyl-L-carnitine supplements. These include nausea, vomiting, abdominal cramps and diarrhea.
Increased agitation has been reported in some with
Alzheimer's disease when taking oral acetyl-L-carnitine. In those with
seizure disorders, an increase in seizure frequency and/or severity has
been reported in some taking this substance. The incidence of this in this
population is low.
Therapy with the nucleoside analogues didanosine (ddI),
zalcitabine (ddC) and stavudine (d4T) may lead to decreased acetyl-L-carnitine
Therapy with valproic acid and the pivalic acid-containing
antibiotics may lead to secondary L-carnitine deficiencies (see L-carnitine).
There are no reports of overdosage.
DOSAGE AND ADMINISTRATION
Typical doses of supplemental acetyl-L-carnitine are
500 milligrams to 2 grams daily in divided doses.
Brooks JO 3d, Yesavage JA, Carta A, Bravi D. Acetyl-L-carnitine
slows decline in younger patients with Alzheimer's disease: a reanalysis
of a double-blind, placebo-controlled trial using the trilinear approach.
Int Psychogeriatr. 1998; 10:193-203.
Chuang WW, Lin WW, Lamb DJ, Lipshultz LI. Effect of
acetylcarnitine on sperm motility. J Urol. 2000; 163(4 Suppl):Abstract1324.
Famularo G, Morreti S, Marcellini S, et al. Acetyl-carnitine
deficiency in AIDS patients with neurotoxicity on treatment with antiretroviral
nucleoside analogues. AIDS. 1997; 11:185-190.
Gorini A, D'Angelo A, Villa RF. Action of L-acetylcarnitine
on different cerebral mitochondrial populations from cerebral cortex. Neurochem
Res. 1998; 23:1485-1491.
Hagen TM, Ingersoll RT, Wehr CM, et al. Acetyl-L-carnitine
fed to old rats partially restores mitochondrial function and ambulatory
activity. Proc Natl Acad Sci USA. 1998; 95:9562-9566.
Hagen TM, Wehr CM, Ames BN. Mitochondrial decay in
aging. Reversal through supplementation of acetyl-L-carnitine and N-tert-butyl-alpha-phenyl-nitrone.
Ann NY Acad Sci. 1998; 854,214-223.
Lolic MM, Fiskum G, Rosenthal RE. Neuroprotective
effects of acetyl-L-carnitine after stroke in rats. Ann Emerg Med. 1997;
Moncada ML, Vicari E, Cimino C, et al. Effect of acetylcarnitine
treatment in oligoasthenospermic patients. Acta Eur Fertil. 1992: 23:221-224.
Onofrj M, Fulgente T, Melchiadona D, et al. L- acetylcarnitine
as a new therapeutic approach for peripheral neuropathies with pain. Int
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Pettegrew JW, Klunke WE, Panchalingam K. Clinical
and biochemical effects of acetyl-L-carnitine in Alzheimer's disease. Neurobiol
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Piovesan P, Quatrini G, Pacifici L, et al. Acetyl-L-carnitine
restores choline acetyltransferase activity in the hippocampus of rats
with partial unilateral fimbria-fornix transection. Int J Dev Neurosci.
Salvioli G, Neri M. L-acetylcarnitine treatment of
mental decline in the elderly. Drugs Exp Clin Res. 1994; 20:169-176.
Sano M, Bell K, Cote L, et al. Double-blind parallel
pilot study of acetyl levocarnitine in patients with Alzheimer's disease.
Arch Neurol. 1992; 49:1137-1141.
Thal LJ, Carta A, Clarke WR, et al. A one year multicenter
placebo-controlled study of acetyl-L-carnitine in patients with Alzheimer's
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White HL, Scates PW. Acetyl-L-carnitine as a precursor
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