Gabapentin in the treatment of neuropathic pain.

This paper reviews the pharmacology and clinical effectiveness of gabapentin in the treatment of neuropathic pain. Gabapentin has antihyperalgesic and antiallodynic properties but does not have significant actions as an anti-nociceptive agent. Its mechanisms of action appear to be a complex synergy between increased GABA synthesis, non-NMDA receptor antagonism and binding to the alpha2delta subunit of voltage dependent calcium channels. The latter action inhibits the release of excitatory neurotransmitters. Clinically, several large randomized controlled trials have demonstrated its effectiveness in the treatment of a variety of neuropathic pain syndromes. Patients with neuropathic pain can expect a mean reduction in pain score of 2.05 points on an 11 point numerical rating scale compared with a reduction of 0.94 points if they had taken the placebo. Around 30% of patients can expect to achieve more than 50% pain relief and a similar number will also experience minor adverse events; the most common of which are somnolence and dizziness. In patients with neuropathic pain due to cancer, higher response rates might be observed with gabapentin when administered with opioids because of a synergistic interaction.