[Gabapentin (Neurontin) and cancer pain: a pilot study]

Gabapentin (GBP) is a new antiepileptic agent with an original spectrum of activity. Its mechanism of action has not yet been fully elucidated but appears not to involve binding to GABA receptors despite being a structural analogue of GABA and is distinct from tricyclic antidepressants (TCAs). It has been shown to modulate high threshold calcium currents in brain neurons. As some other anticonvulsants, GBP has been recently proposed for the treatment of noncancer neuropathic pain like diabetic neuropathy and post herpetic neuralgia (double blind studies with placebo). We prospectively followed 20 cancer patients with advanced disease suffering from neuropathic pain. All were already treated for their pain syndrome. We started with 300 mg of GBP given orally in order to reach a dose of 900 mg on D3. All coanalgesics were stopped before entering the study. The only relevant side effect due to GBP was somnolence, otherwise time limited. GBP treatment was associated with a decrease of opioids doses in 9 patients and a decrease of VAS for pain intensity in all cases. Furthermore, the need of rescue doses decreased in all cases but 2. GBP appears to be one of the most effective drugs for the treatment of neuropathic pain. It is well tolerated and its effectiveness appears shortly after its administration. A synergistic action with opioids is suggested. Despite the small number of patients, our study suggests that GBP could be a treatment of neuropathic pain in cancer. Comparative trials should be performed with other neuropathic pain drugs including TCAs and antiepileptic drugs, especially carbamazepine.