Background: Dementia is a common mental health problem affecting 5% of those over 65. Various pathological processes are linked to memory impairment in dementia, particularly those affecting the cholinergic neurotransmitter system. Acetyl-l-carnitine (ALC) is derived from carnitine and is described as having several properties which may be beneficial in dementia. This includes activity at cholinergic neurons, membrane stabilization and enhancing mitochondrial function. Work on the effects of ALC has been ongoing since the 1980s yet the efficacy of ALC in cognitive decline remains unclear. Early studies suggested a beneficial effect of ALC on cognition and behaviour in aging subjects. However, later, larger studies have not supported these findings. Some of the difficulties lie in the early and later studies differing widely in methodology and assessment tools used, and are therefore difficult to compare. ALC is not currently in routine clinical use.
Objectives: The objective of this review is to establish whether Acetyl-l-carnitine is clinically effective in the treatment of people with dementia.
Search strategy: The trials were identified from a search of the Specialized Register of the Cochrane Dementia and Cognitive Improvement Group on 8 January 2003 using the terms acetyl-l-carnitine, l-carnitine acetyl ester, acetylcarnitine.
Selection criteria: All double-blind, randomized, trials involving people with dementia in which treatment with ALC was compared with a placebo group
Data collection and analysis: Data were extracted by a reviewer (SH) and entered into Revman 4.1 software. Where possible intention-to-treat data were used, but most of the analyses were of completers (people who completed the study).
Main results: There are 11 included trials, all of which had restricted the participants to people with Alzheimer's disease. All trials assessed the cognitive effects of ALC and in addition six considered severity of dementia, six considered functional ability and six considered clinical global impression. There were statistically significant treatment effects in favour of ALC at 12 and 24 weeks for the numbers showing improvement as determined by Clinical Global Impression, [OR 2.33, 95% CI 1.25 to 4.35, P<0.01] and [OR 3.91, 95% CI 1.32 to 11.54, P=0.01] but not as determined by the CIGIC at 52 weeks. There was no evidence of benefit for ALC in the areas of cognition, severity of dementia, functional ability or Clinical Global Impression as a continuous measure. Various adverse events were reported, but from the meta-analyses there were no statistically significant differences between treated and placebo groups.
Reviewer's conclusions: There is evidence for benefit of ALC on clinical global impression, but there was no evidence using objective assessments in any other area of outcome. Given the large number of comparisons made, the statistically significant result may be due to chance. At present there is no evidence to recommend its routine use in clinical practice. Although the intention of the review was to access ALC for the treatment of all dementias, the included trials had confined themselves to participants with Alzheimer's disease. Individual patient data may add to the findings, as would trials including other types of dementia and other outcomes (e.g. mood and caregiver quality of life). However, the evidence does not suggest that ALC is likely to prove an important therapeutic agent. More work on the pharmacokinetics of ALC in humans is also required.