Acetyl-L-carnitine in chronic pain: A narrative review

Acetyl-L-carnitine (ALC) is an endogenous molecule that not only plays a role in energy metabolism, but also has antioxidant properties, protects from oxidative stress, modulates brain neurotransmitters such as acetylcholine, serotonin and dopamine, and acts on neurotrophic factors such as nerve growth factor (NGF) and metabotropic glutamate (mGlu) receptors by means of epigenetic mechanisms. Importantly, it induces mGlu2 expression at nerve terminals, thus giving rise to analgesia and preventing spinal sensitisation. It has also been found to have even long-term neurotrophic and analgesic activity in experimental models of chronic inflammatory and neuropathic pain. The aim of this narrative review is to summarise the current evidence regarding the use of ALC in patients with chronic pain, and cognitive and mood disorders, and investigate the rationale underlying its use in patients with fibromyalgia syndrome, which is characterised by nociplastic changes that increase the sensitivity of the nervous system to pain.