Acetylcarnitine

Form of L carnitine

Acetyl L carnitine, ALCAR or ALC, is an acetylated form of L carnitine. It is naturally produced by the human body, and it is available 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.

Carnitine and ALCAR supplements carry warnings of a risk that they promote seizures in people with epilepsy, but a 2016 review found this risk to be based only on animal trials.

Peripheral neuropathy: Meta analyses from 2015 and 2017 both conclude that the current evidence suggests ALC reduces pain from peripheral neuropathy with few adverse effects. The 2017 review also suggested ALC improved electromyographic parameters. Both called for more randomized controlled trials. An updated Cochrane review in 2019 of four studies with 907 participants was very uncertain as to if ALC caused a pain reduction after 6 to 12 months of treatment. Chemotherapy induced peripheral neuropathy (CIPN): A review of two studies concluded that ALC may be a treatment option for paclitaxel and cisplatin induced CIPN, while a clinical trial showed it did not prevent CIPN and appeared to worsen the conditions in taxane therapy. Male infertility: Scientific reviews from 2016 and 2014 showed mixed results, with some studies showing a positive relationship between ALC and sperm motility, and others showing no relationship. Dementia: A 2003 Cochrane review sought to determine the safety and efficacy of ALCAR in dementia but the reviewers found only clinical trials studies on Alzheimer's disease; the review found that the pharmacology of ALCAR was poorly understood and that based on the lack of efficacy, ALCAR was unlikely to be an important treatment for AD. Depression: One 2014 review assessed the use of ALCAR in fourteen clinical trials for various conditions with depressive symptoms; the trials were small (ranging from 20 to 193 subjects) and their design was so different that results could not be generalized; most studies showed positive results and a lack of adverse effects. The mechanism of action by which ALCAR could treat depression is not known. A meta analysis from 2014 concluded that ALCAR could only be recommended for the treatment of persistent depressive disorder if publication bias was deemed improbable. A 2018 systematic review and meta analysis of 12 randomized controlled trials found "supplementation significantly decreases depressive symptoms compared with placebo/no intervention, while offering a comparable effect with that of established antidepressant agents with fewer adverse effects." The review also indicates that "the effect of ALC in younger subjects was not more effective than placebo in improving these symptoms." indicating a need for more research explaining the age/effect relation. Fragile X syndrome: A 2015 Cochrane review of ALCAR in fragile X syndrome found only two placebo controlled trials, each of low quality, and concluded that ALCAR is unlikely to improve intellectual functioning or hyperactive behavior in children with this condition. Hepatic encephalopathy: ALCAR has been studied in hepatic encephalopathy, a complication of cirrhosis involving neuropsychiatric impairment; ALCAR improves blood ammonia levels and generates a modest improvement in psychometric scores but does not resolve the condition – it may play a minor role in managing the condition.

In a small clinical study, when ALCAR was administered intravenously and insulin levels were held steady and a meal low in carnitine but high in carbohydrates was taken by healthy young men, ALCAR appeared to decrease glucose consumption in favor of fat oxidation. Memory performance declines with age. These increases in decay and damage, and memory loss itself, can be partially reversed in old rats by feeding acetyl L carnitine.