Gabapentin and pain: From the laboratory to the clinic

Gabapentin is an antiepileptic that has been marketed in the last decade. It is better tolerated than traditional antiepileptics and has been included in several analgesic therapies. Its analgesic effect has been studied at pre-clinical and clinical level. It has been determined that in normal physiological conditions, gabapentin has no analgesic effects on acute pain, but may enhance opiate analgesia. Using animal models its possible efficacy in post-operative pain and certain types of inflammatory tonic pain has been postulated. Many current pre-clinical studies, clinical observations and clinical trials describe the efficacy of gabapentin in several types of chronic pain, mainly neurogenic. From the comparative and randomised clinical trials performed with gabapentin, it can be concluded that it is effective in diabetic neuropathy and postherpetic neuralgia when it is administered in doses over 900 mg/day. Gabapentin has also found to be effective for controlling pain and spasticity associated with multiple sclerosis. It is needed to perform controlled clinical trials aimed at comparing gabapentin with traditional therapies, to characterise the analgesic effect of the drug and to optimise its clinical use. The mechanism of the analgesic effect of gabapentin is still unknown, though most researchers link it to the modulation of the activity of certain types of voltage-dependent Ca2+ channels. It is postulated that gabapentin would thus have inhibitory actions at a central or peripheral level that would explain its analgesic effect.