Benefits according to published studies:
May be helpful in those with Alzheimer's disease. Acetyl l carnitine protects against amyloid-beta neurotoxicity.
Acetyl l carnitine may benefit individuals with degenerative cerebellar ataxia.
Acetyl l carnitine may benefit those with mental fatigue associated with chronic fatigue syndrome.

Patients with multiple sclerosis may benefit from acetyl carnitine, which could reduce their fatigue.

In aging rats, chronic administration of acetyl carnitine increases cholinergic synaptic transmission and consequently enhances learning capacity. The memory of aging rats is rejuvenated by giving them a combination of acetyl l carnitine and alpha lipoic acid.

Acetyl l carnitine may benefit those with diabetic neuropathy. This nutrient could be helpful in chemotherapy induced peripheral neuropathy.

May reduce alcohol-induced cellular damage to organs.

ALCAR benefits geriatric patients with mild depression.

Acetyl l carnitine improves the function of mitochondria, the organelles within cells that are involved in energy production.

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

Acetyl carnitine is suitable for clinical use in the reduction of neuronal death after peripheral nerve trauma.

ADHD
L-acetylcarnitine may help with attention deficit hyperactivity disorder (ADHD) in children with the genetic disorder known as fragile X syndrome. Fragile X syndrome results from an inherited genetic defect on the X chromosome. It is associated with  mental retardation and may also cause autism and ADHD, ADHD is common in young boys with fragile X syndrome. 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 in patients treated with acetylcarnitine. American Journal of Medical Genetics 2008.

Cataracts
The effect of acetyl-l-carnitine on lenticular calpain activity in prevention of selenite-induced cataractogenesis.
Exp Eye Res. 2008 December. Elanchezhian R, Sakthivel M, Geraldine P, Thomas PA. Elanchezhian R, Sakthivel M. Department of Animal Science, School of Life Sciences, Bharathidasan University, Tiruchirappalli 620 024, Tamil Nadu, India.
The present study sought to determine whether acetyl-l-carnitine (ALCAR) prevents selenite cataractogenesis by mechanisms involving lenticular calpain activity, Wistar rat pups were divided into 3 groups of 15 each. Group I (normal) rats received an intraperitoneal (i.p.) injection of normal saline on postpartum day 10; Group II (cataract-untreated) rats received a single subcutaneous (s.c.) injection of sodium selenite (19mumol/kg body weight) on postpartum day 10; Group III (cataract-treated) pups received a single s.c. injection of sodium selenite on postpartum day 10 and intraperitoneal injections of acetyl-l-carnitine (200mg/kg body weight) on postpartum days 9-14. At the end of the study period (postpartum day 16), both eyes of each rat pup were examined by slit-lamp biomicroscopy. Our results suggest that, in addition to its already-described antioxidant potential, acetyl-l-carnitine prevents selenite cataractogenesis by maintaining calpain activity at near normal levels. These findings may stimulate further efforts to develop acetyl-l-carnitine as a novel drug for prevention of cataract.

Acetyl l Carnitine and propionyl l carnitine for erectile dysfunction
Acetyl-L-carnitine plus propionyl-L-carnitine improve efficacy of sildenafil in treatment of erectile dysfunction after bilateral nerve-sparing radical retropubic prostatectomy.
Urology. 2005 Nov;66(5):1080-5.
Operative Unit of Andrology, Societa Italiana di Medicina della Riproduzione, Bologna, Italy.
To determine whether propionyl-L-carnitine (PLC) plus acetyl-L-carnitine improve the effectiveness of sildenafil in restoring sexual potency after bilateral nerve-sparing radical retropubic prostatectomy. We analyzed the data from 96 patients who had undergone bilateral nerve-sparing radical retropubic prostatectomy: 33 were given placebo (group 1), 32 used PLC 2 g/day plus acetyl-l-carnitine 2 g/day plus sildenafil 100 mg when needed (group 2), and 35 used sildenafil alone (group 3). Placebo proved ineffective and sildenafil and sildenafil plus acetyl-l-carnitine and PLC proved effective. The International Index of Erectile Function-15 scores of the group 2 patients were significantly greater than those of group 3 in the following domains: erectile function, sexual intercourse satisfaction, orgasm, and general sexual well-being. The drugs did not significantly modify the score in the sexual desire domain or in the peak systolic velocity or end-diastolic velocity of the cavernosal arteries. Acetyl-l-carnitine plus propionyl-L-carnitine did not significantly improve the side effects of sildenafil. Propionyl-L-carnitine and acetyl-l-carnitine proved to be safe and reliable in improving the efficacy of sildenafil in restoring sexual potency after bilateral nerve-sparing radical retropubic prostatectomy.

Fibromyalgia
Double-blind, multicenter trial comparing acetyl l-carnitine with placebo in the treatment of fibromyalgia patients.
Clin Exp Rheumatol. 2007 Mar-April Rossini M, Di Munno O, Valentini G, Bianchi G, Biasi G, Cacace E, Malesci D, La Montagna G, Viapiana O, Adami S. Rheumatology Unit, University of Verona, Italy.
One hundred and two patients meeting the American College of Rheumatology criteria for fibromyalgia syndrome were randomized into the study. The treatment consisted of 2 capsules/day of 500 mg acetyl l-carnitine or placebo plus one intramuscular (i.m.) injection of either 500 mg acetyl l-carnitine or placebo for 2 weeks. During the following 8 weeks the patients took 3 capsules daily containing either 500 mg acetyl l-carnitine or placebo. The patients were seen during treatment after 2 (visit 3), 6 (visit 4) and 10 weeks (visit 5). The patients were also visited 4 weeks after treatment discontinuation (follow-up visit).  The "total myalgic score" and the number of positive tender points declined significantly and equally in both groups until the 6th week of treatment. At the 10th week both parameters remained unchanged in the placebo group but they continued to improve in the acetyl l-carnitine group with a statistically significant between-group difference. Although this experience deserves further studies, these results indicate that acetyl l-carnitine may be of benefit in patients with fibromyalgia, providing improvement in pain as well as the general and mental health of these patients.

HIV treatment
Acetyl-l-carnitine and nucleoside reverse transcriptase inhibitor-associated neuropathy in HIV infection.
HIV Med. 2009 February. Valcour V, Yeh TM, Bartt R, Clifford D, Gerschenson M, Evans SR, Cohen BA, Ebenezer GJ, Hauer P, Millar L, Gould M, Tran P, Shikuma C, Souza S, McArthur JC; AIDS Clinical Trials Group (ACTG) 5157 protocol team. Hawaii AIDS Clinical Research Program, John A. Burns School of Medicine, University of Hawaii, Honolulu, HI, USA.
Antiretroviral toxic neuropathy (ATN) is associated with dideoxynucleoside reverse transcriptase inhibitor use in patients infected with HIV, possibly as a result of mitochondrial toxicity. Acetyl-l-carnitine (ALC) has been linked to symptomatic improvement in ATN. We present an open-label single-arm pilot study to evaluate changes in intra-epidermal nerve fibre (IENF) density and mitochondrial DNA (mtDNA) copies/cell among subjects treated with 3000 mg Acetyl-l-carnitine daily. Twenty-one subjects completed the study. Acetyl-l-carnitine was generally well tolerated. The IENF density did not change in cases completing 24 weeks of Acetyl-l-carnitine therapy. Fat mtDNA copies/cell did not change with therapy. Improvements in neuropathic pain, paresthesias, and symptoms of numbness were noted. Similarly, improvement was noted on the Gracely Pain Intensity Score. Acetyl-l-carnitine therapy coincided with improvements in subjective measures of pain in this open-label single-arm study. However, changes were not observed in objective measures of IENF density or mtDNA levels, providing little objective support for use of Acetyl-l-carnitine in this setting.

MDMA use
Acetyl-l-carnitine provides effective in vivo neuroprotection over 3,4-methylenedioximethamphetamine-induced mitochondrial neurotoxicity in the adolescent rat brain.
Neuroscience. 2009 January.
3,4-Methylenedioximethamphetamine MDMA, ecstasy is a worldwide abused stimulant drug, with persistent neurotoxic effects and high prevalence among adolescents. The massive release of serotonin from pre-synaptic storage vesicles induced by MDMA followed by monoamine oxidase B (MAO-B) metabolism, significantly increases oxidative stress at the mitochondrial level. l-Carnitine and its ester, acetyl-l-carnitine (ALC), facilitate the transport of long chain free fatty acids across the mitochondrial membrane enhancing neuronal anti-oxidative defense. Here, we show the potential of acetyl l carnitine against the neurotoxic effects of MDMA exposure. The present work is the first to successfully demonstrate that pretreatment with acetyl l carnitine exerts effective neuroprotection against the MDMA-induced neurotoxicity at the mitochondrial level. These results indicate potential benefits of acetyl l carnitine application in the prevention and treatment of neurodegenerative disorders.

Acetyl l Carnitine and methadone, opiate withdrawal
Acetyl-l-Carnitine in the Management of Pain During Methadone Withdrawal Syndrome.
Clin Neuropharmacol. 2008 October. *Department of Psychiatry-Additive Behaviours Unit, Catholic University Medical School, Rome; daggerDepartment of Pharmacology, University of Florence, Florence; and double daggerSigma-Tau S.p.A., Rome, Italy.
This study was designed to determine the short-term effect of acetyl-l-carnitine (ALC) on symptoms of withdrawal in opiate-dependent subjects and animals and, in particular, on pain, given the efficacy of acetyl-l-carnitine in other typologies of pain. Thirty subjects meeting clinical criteria for methadone dependence were consecutively recruited and treated with acetyl-l-carnitine 2 g/d or placebo for a 3-week detoxification period. Acetyl-L-carnitine acted as an effective antihyperalgesic agent for relieving opiate-withdrawal hyperalgesia in animals and displayed clinical efficacy on other withdrawal symptoms such as muscular tension, muscular cramps, and insomnia. Considering its tolerability, the excellent side effect profile, the absence of significant interactions, and the lack of abuse potential, acetyl-l-carnitine can be considered as a useful pharmacological adjunct in the treatment of opiate withdrawal.

Sperm health and sperm motility
Clinical efficacy of combined L-carnitine and acetyl-L-carnitine on idiopathic asthenospermia
Zhonghua Nan Ke Xue. 2008 Feb; Department of Andrology, International Peace Maternity and Child Health Hospital, Shanghai Jiaotong University School of Medicine, Shanghai 200030, China.
To evaluate the clinical efficacy of combined L-carnitine and acetyl-L-carnitine on idiopathic asthenospermia. Thirty patients with idiopathic asthenospermia were treated by combined L-carnitine and acetyl-L-carnitine for 3 months after failure to respond to the integrated therapy of Chinese and Western medicine.Combined L-carnitine and acetyl-L-carnitine statistically improved the sperm vitality, sperm motility and the total sperm count per ejaculate .

Weight loss
High dosages of acetyl l carnitine may help reduce appetite, but a more effective product for appetite suppression and weight loss is Diet Rx.

Forms of Acetyl l Carnitine
You may come across other forms of acetyl carnitine such as acetyl l carnitine arginate and propionyl l carnitine. We are not certain whether acetyl l carnitine arginate or other variants offer any advantages over acetyl carnitine. Time will tell.

Q. I have been getting email promotions regarding the benefits of acetyl l carnitine arginate. Have there been studies with acetyl l carnitine arginate that show it to be superior to acetyl l carnitine?
   A. As of 2008, we are not aware of human studies comparing acetyl l carnitine to acetyl l carnitine arginate. Acetyl l carnitine supplements work quite well to improve mental function, we are not sure if the arginate form adds any additional benefits.

Q. Is acetyl l carnitine hcl different than plain acetyl l carnitine?
   A. We have no reason to believe acetyl l carnitine hcl has properties different than that of acetyl l carnitine.

Q. I have sometimes seen acetyl l carnitine with an n added before it, n acetyl l carnitine. Is there a difference between the two?
   A. N acetyl l carnitine and acetyl l carnitine are the same supplement.

Comparison of pharmacokinetics of L-carnitine, acetyl-L-carnitine and propionyl-L-carnitine after single oral administration of L-carnitine in healthy volunteers.
Clin Invest Med. 2009 February. The Affiliated Hospital of Medical College, Qingdao University, Qingdao, China.
To investigate the pharmacokinetics of L-carnitine and its analogues, acetyl-L-carnitine and propionyl-L-carnitine in healthy volunteers after single L-carnitine administration. Liquid L-carnitine (2.0 g) was administered orally as a single dose in 12 healthy subjects. Plasma and urine concentrations of L-carnitine, ALC and PLC were detected by HPLC. L-carnitine has a greater maximum plasma concentration than acetyl-L-carnitine and propionyl-L-carnitine. L-carnitine also has a longer half-life than acetyl-L-carnitine and propionyl-L-carnitine. These data may have important implications in the designing of dosing regimens for L-carnitine or its analogues, such as acetyl-L-carnitine or propionyl-L-carnitine.

Influence on the brain and nervous system
Acetyl-L-carnitine is a naturally occurring substance that is neuroprotective. ALC plays an essential role in intermediary and mitochondrial metabolism. It has also nerve regenerating and antioxidant actions. ALC has potential in the treatment of neuropathies of various causes, and it is a molecule of considerable interest for its clinical application in various neural disorders, such as Alzheimer's disease and painful neuropathies. In rodent brain studies, KAC up-regulates of the expression of prostaglandin D(2) synthase, brain-specific Na(+)-dependent inorganic phosphate transporter, and cytochrome b oxidase, bc1 complex. ALC treatment down-regulates the expression of the gene of ferritin-H. ALC protects nerve cells against various brain stressors.

Various Forms provided by Sigma Tau corp:
These are Acetyl L-Carnitine Hydrochloride
Acetyl L-Carnitine Galactarate (US PATENT 5952379)
Acetyl L-Carnitine Arginate Dihydrochloride - As of May 2009, human studies with this supplement could not be found in medical journals.
Acetyl L-Carnitine Taurinate Hydrochloride
Acetyl L-Carnitine Hydrogen Fumarate
Acetyl L-Carnitine L-Leucinate Hydrochloride
Acetyl L-Carnitine 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.

Acetyl l carnitine and alpha lipoic acid
Some dietary supplements include a combination of acetyl l carnitine and alpha lipoic acid. Although the combination of these two nutrients could be healthy, many acetyl l carnitine and alpha lipoic acid products have too high dosages of these nutrients and side effects could occur. We suggest using no more than 100 mg of acetyl l carnitine and no more than 20 mg of alpha lipoic acid when combining the two for long term use.

Q. I bought a product that had alpha lipoic acid acetyl l carnitine in a dosage of 100 mg and 500 mg. Is this too high a dosage?
   A. Yes, this alpha lipoic acid acetyl l carnitine combination could lead to overstimulation and insomnia and perhaps heart rhythm distrubances.