Acetyl-L-carnitine in neuropathic pain: experimental data.

Acetyl-L-carnitine (ALC) has gained clinical interest for its analgesic effect in different forms of neuropathies associated with chronic pain, such as diabetic and HIV-related peripheral neuropathies. The antinociceptive effect of ALC has been confirmed in several experimental models of neuropathic pain, including streptozotocin- and chemotherapy-induced neuropathy, and the sciatic nerve chronic constriction injury model. In these models, prophylactic administration of ALC has proven to be effective in preventing the development of neuropathic pain. In addition, ALC is known to produce a strong antinociceptive effect when given after neuropathic pain has been established. ALC can also improve the function of peripheral nerves by increasing nerve conduction velocity, reducing sensory neuronal loss, and promoting nerve regeneration. Analgesia requires repeated administrations of ALC, suggesting that the drug regulates neuroplasticity across the pain neuraxis. Recent evidence indicates that ALC regulates processes that go beyond its classical role in energy metabolism. These processes involve the activation of muscarinic cholinergic receptors in the forebrain, and an increased expression of type-2 metabotropic glutamate (mGlu2) receptors in dorsal root ganglia neurons. Induction of mGlu2 receptors is mediated by acetylation mechanisms that involve transcription factors of the nuclear factor (NF)-kappaB family.