Potential benefits according to published studies

ADHD benefit, reduction of attention deficit
L-Acetylcarnitine may help with attention deficit hyperactivity disorder in children with the genetic disorder known as fragile X syndrome which results from an inherited genetic defect on the X chromosome. It is associated with  mental retardation and may also cause autism and ADHD, Dr. Giovanni Neri from Universita Cattolica in Rome studied boys between 6 and 13 years old for a period one year. Twenty four received l-acetylcarnitine and 27 received placebo. There was a more effective reduction of hyperactivity and improvement of social behavior. American Journal of Medical Genetics, 2008.

Alzheimer's disease, dementia
May be helpful in those with Alzheimer's disease since It protects against amyloid-beta neurotoxicity.

Acetylcarnitine (carnicetine) in the treatment of early stages of Alzheimer's disease and vascular dementia.
Zh Nevrol Psikhiatr Im S S Korsakova. 2011 Efficacy, safety and tolerability of acetylcarnitine (ALC) were studied during the double-blind placebo-controlled 12-week trial in patients with mild dementia caused by the Alzheimer's disease (AD) and vascular dementia (VD). ALC was administered in doses from 2250 to 3000 mg per day. Patient's state was assessed with some scales (MMSE, CGI) and a battery of neuropsychological tests. The treatment effect of ALC was 2.8 times higher than in placebo-treated patients. The clinical improvement by CGI scores was significantly better in AD patients compared to VD and did not depend on the severity of baseline cognitive deficit. The drug was well-tolerated. Carnicetine can be recommended in the abovementioned doses for treatment of early stages of AD and VD.
   Note: I think much lower dosages should be used since my concern is that high amounts could disturb sleep.

Effects of acetylcarnitine in Alzheimer's disease patients unresponsive to acetylcholinesterase inhibitors.
Current Medical Research Opin. 2003.
An evaluation was made of the effect of 2 grams / day orally for 3 months in association with donepezil or rivastigmine in 23 patients with mild AD who had not responded to treatment with acetylcholinesterase inhibitors (AChE-I). The response rate, which was 38% after AChE-I treatment, increased to 50% after the addition of acetylcarnitine.

Anti-aging and longevity with alpha lipoic acid, effect on mitochondria
Scientists at the University of California, Berkeley, CA rejuvenated aging rats by giving them a combination of alpha lipoic acid and acetylcarnitine. Lead researcher Dr Bruce Ames, said the results were astonishing: "With the two supplements together, these old rats got up and did the Macarena. The brain looks better, they are full of energy - everything we looked at looks more like a young animal." The animals' memories improved. The two chemicals in combination have a positive impact on mini-organs within the body's cells called mitochondria and were able to mop up free radicals. Mitochondria generate energy within the cells and  their deterioration is an important cause of aging.
   It is difficult to predict whether this combination is effective in humans as an anti-aging combination, and if so, how to determine the ideal dose combination. In the meantime, those who wish to supplement prudently with small amounts may consider taking  about 5 to 10 mg of alpha lipoic acid, and 30 to 100 mg of acetylcarnitine. Since these nutrients are not often available over the counter in these small doses, you may need to open the capsules and take a portion.

Q. Dr. Sahelian seems to be recommending lower dosages of acetyl carnitine and alpha lipoic acid, as a daily anti-aging regimen. It looks like he's saying 30 mg of alpha lipoic acid and 100mg of acetyl carnitine. I'm 66 and have been taking the Juvenon dosage ( 500 acetyl and 200 alpha lipoic ) of these things for years, one capsule in the morning, and YES, have had sleep problems, but that may just be from aging, I'm not sure. But it seems like everyone sells those dosages ( I cant afford the Juvenon prices and have been buying generic ones ) and no one sells the lower regimen doses that Dr. Sahelian appears to be recommending. Would these lower dosages help sleep, while at the same time help reduce aging?
   A. I do not know for sure how it will effect aging, but lower dosages would certainly reduce the risk for insomnia or sleep problems.

Chronic fatigue syndrome CHF
Exploratory open label, randomized study of acetyl- and propionylcarnitine in chronic fatigue syndrome.
Psychosom Med. 2004.
We compared 2 grams a day acetylcarnitine, 2 g/d propionyl-L-carnitine, and its combination in 3 groups of 30 chronic fatigue syndrome patients during 24 weeks. The first significantly improved mental fatigue and propionylcarnitine improved general fatigue.

Depression and low mood
ALCAR may benefit geriatric patients with mild depression although there are more effective dietary supplements for this purpose including 5-HTP, St. John's wort, and SAM-e.

J Psychiatr Res. 2014. A review of current evidence for acetyl-l-carnitine in the treatment of depression. ALC may be potentially effective and tolerable next treatment option with novel action mechanisms for patients with depression, in particular older population and patients with comorbid medical conditions who are vulnerable to adverse events from antidepressants.

Int J Mol Sci. 2017. l-Acetylcarnitine: A Mechanistically Distinctive and Potentially Rapid-Acting Antidepressant Drug. This nutirient is currently marketed for treatment of neuropathic pain. Recent preclinical and clinical data suggested that LAC may exert antidepressant effects with a more rapid onset than conventional drugs.

Diabetic neuropathy pain
Acetylcarnitine has demonstrated neuroprotective effects in several experiments and is widely prescribed to reduce cognitive impairment in Alzheimer's disease patients or manage neuropathic symptoms in diabetic patients.

Acetylcarnitine in the treatment of diabetic neuropathy. A long-term, randomized, double-blind, placebo-controlled study.
Drugs R D. 2002.
A group of 333 patients with diabetic neuropathy were enrolled. Acetylcarnitine (or placebo) was given orally at a dosage of 2000 mg/day. This natural medicine was effective and well tolerated in improving neurophysiological parameters and in reducing pain over a 1-year period.

AcetylCarnitine Improves Pain, Nerve Regeneration, and Vibratory Perception in Patients With Chronic Diabetic Neuropathy: An analysis of two randomized placebo-controlled trials.
Diabetes Care. 2005.
We evaluated frozen databases from two 52-week randomized placebo-controlled clinical diabetic neuropathy trials testing two doses of acetylcarnitine: 500 and 1,000 mg/day three times a day. Data showed significant improvements in sural nerve fiber numbers and regenerating nerve fiber clusters. Nerve conduction velocities and amplitudes did not improve, whereas vibration perception improved in both studies. Pain as the most bothersome symptom showed significant improvement in one study and in the combined cohort taking 1,000 mg.

Erectile dysfunction, impotence
Acetylcarnitine plus propionyl-L-carnitine improve efficacy of sildenafil in treatment of erectile dysfunction after bilateral nerve-sparing radical retropubic prostatectomy.
Urology. 2005.
Data from 96 patients who had undergone bilateral nerve-sparing radical retropubic prostatectomy was reviewed: 33 were given placebo, 32 used propionyl-L-carnitine 2 g/day plus acetylcarnitine 2 g/day plus sildenafil 100 mg when needed, and 35 used sildenafil alone. Placebo proved ineffective and sildenafil and sildenafil plus acetylcarnitine and PLC proved effective in restoring sexual potency after bilateral nerve-sparing radical retropubic prostatectomy.

Exercise, physical activity, sports performance
Eur J Nutr. 2014. Effect of carnitine, acetyl-, and propionylcarnitine supplementation on the body carnitine pool, skeletal muscle composition, and physical performance in mice. Oral supplementation of carnitine, acetylcarnitine, or propionylcarnitine in mice is associated with increased plasma and urine total carnitine concentrations, but does not affect the skeletal muscle carnitine content. Despite better preservation of skeletal muscle glycogen and lower plasma lactate levels, physical performance was not improved by carnitine or acylcarnitine supplementation.

Fertility, infertility, sperm motility
Still being studied, may help with sperm motility.

Hypertension and insulin resistance
Ameliorating hypertension and insulin resistance in subjects at increased cardiovascular risk: effects of acetylcarnitine therapy.
Hypertension. 2009.
We prospectively evaluated the effects of 24-week oral acetylcarnitine 1 g twice daily therapy on the glucose disposal rate in nondiabetic subjects at increased cardiovascular risk. It safely ameliorated arterial hypertension, insulin resistance, impaired glucose tolerance, and hypoadiponectinemia.

Liver health
Metab Brain Disorder. 2013. Acetylcarnitine in hepatic encephalopathy. This nutrient induces ureagenesis leading to decreased blood and brain ammonia levels and treatment decreases the severity of mental and physical fatigue, depression cognitive impairment and improves health-related quality of life.

Memory improvement, mental enhancement, effect on brain
Studies in aging rats shows chronic administration increases cholinergic synaptic transmission (acetylcholine brain chemical) and consequently enhances learning capacity. The memory of aging rats is rejuvenated by giving them a combination of acetylcarnitine and lipoic acid. I am not sure how it specifically affects the cerebrum or cerebellum. I am not fully clear how it influences levels of dopamine, serotonin, norepinephrine, and other neurotransmitter levels in the brain.

Multiple sclerosis
Patients with multiple sclerosis may benefit with a reduction in their fatigue.

Comparison of the effects of acetylcarnitine and amantadine for the treatment of fatigue in multiple sclerosis: results of a pilot, randomised, double-blind, crossover trial.
J Neurol Sci. 2004.
A group of 36 MS patients with fatigue were treated for 3 months with either amantadine (100 mg twice daily) or acetylcarnitine (1 g twice daily). After a 3-month washout period, they crossed over to the alternative treatment for 3 months. The results show that this nutrient is better tolerated and more effective than amantadine for the treatment of MS-related fatigue.

Nerve damage
Not enough human studies to determine benefit in nerve damage.

Neurosci Letters. 2017. Acetyl-l-carnitine enhances myelination of regenerated fibers of the lateral olfactory tract. The study revealed that ALC accelerates myelination of regenerated fibers in neonatally LOT-injured young adult rats.

Neuropathy pain
A pilot study on the effect of acetylcarnitine in paclitaxel- and cisplatin-induced peripheral neuropathy.
Tumori. 2005.
Twenty-seven patients with paclitaxel and/or cisplatin-induced neuropathy received at least one cisplatin or one paclitaxel based regimen, or a combination of both. Patients with chemotherapy-induced peripheral neuropathy were treated with acetylcarnitine 1 g/die i.v. infusion over 1-2 hours for at least 10 days and it seemed to be an effective and well-tolerated agent for the treatment of chemotherapy-induced peripheral neuropathy.

Osteoarthritis, arthritis
Life Sci. 2014. Prophylactic role of acetyl-l-carnitine on knee lesions and associated pain in a rat model of osteoarthritis.. In the present study, our aim was to validate in vivo the prophylactic role of acetyl-l-carnitine (ALC) using an established knee osteoarthritis (OA) animal model which mimics the pathological changes of OA in humans, targeting cartilage and causing chondrocyte death. Our findings show that there is a place for ALC as chondroprotective agents in cartilage degradation and strongly support the prophylactic and therapeutic potentials of ALC in knee-OA patients.

Peyronie's disease
ALCAR is more effective than tamoxifen in the therapy of acute and early chronic Peyronie's disease.

Sperm health, number and volume
Placebo-controlled double-blind randomized trial on the use of L-carnitine, L-acetylcarnitine, or combined in men with idiopathic asthenozoospermia. Fertility & Sterility 2005.
Sixty infertile men, ages 20 to 40 years, underwent a double-blind therapy of L-carnitine 3 g/d, acetylcarntine 3 g/d, a combination, or placebo. Sperm cell motility increased in patients to whom acetylcarnitine was administered both alone or in combination with carnitine; combined therapy led to a significant improvement of straight progressive velocity after 3 months. The administration of this combination is effective in increasing sperm kinetic features in patients affected by idiopathic asthenozoospemia (reduced sperm motility).

Thyroid medication, influence on hypothyroid or hyperthyroid
Q. I am thinking about taking it to help with my memory as I have undergone intensive chemotherapy which has affected my memory. Your site talked about dosage of 300 mg daily with a break, which was helpful because everyone else recommends much more. I am taking medication for an underactive thyroid. I read that acetylcarnitine can interfere with that medication and people with thyroid problems should not take it.
   A. Caution is advised when combining medicines, hormones, and supplements. If your doctor approves you can open a 300 mg capsule and use a third of it the first day. Another option is Mind Power Rx, half a capsule could be used. Most medications and supplements can be used together if the dosages are low.

Vision research study
Improvement of visual functions and fundus alterations in early age-related macular degeneration treated with a combination of acetylcarnitine, n-3 fatty acids, and coenzyme Q10.
Ophthalmologica. 2005.
The aim of this randomized, double-blind, placebo-controlled clinical trial was to determine the efficacy of a combination of acetylcarnitine, n-3 fatty acids, and coenzyme Q10 (Phototrop) on the visual functions and fundus alterations in early age-related macular degeneration. Findings suggest that an appropriate combination of compounds which affect mitochondrial lipid metabolism, may improve and subsequently stabilize visual functions, and it may also improve fundus alterations in patients affected by early age-related macular degeneration.

Weight loss
Some people notice ALC reduces appetite but I have not seen formal studies using this supplement as an effective weight loss pill when used just by itself.

Various forms manufactured and provided by Sigma Tau corp:
Acetyl L-Carnitine hydrochloride
Galactarate
Arginate
Taurinate
Hydrogen Fumarate
L-Leucinate
L-Ornithine Dihydrochloride
     There has not been enough research with each of these forms of ALCAR to determine which are best for long term human consumption.