Felbamate relieves several abnormal pain sensations in rats with an experimental peripheral neuropathy

The antiepileptic drug, felbamate, was tested in a rat model of painful peripheral neuropathy (the chronic constriction injury model). Intraperitoneal doses of 150, 300 and 600 mg/kg were given to animals with established heat-hyperalgesia, mechanohyperalgesia, mechano-allodynia and signs of spontaneous pain (hindpaw guarding). Postinjection tests were conducted 2, 6, 12, 24 and 48 h later. The 150 mg/kg dose had little or no effect on any measure. Significant reductions in all measures of abnormal pain were seen after the 300 and 600 mg/kg doses; relief lasted 2 to 12 h. Side effects were trivial or absent by 2 h postinjection. Felbamate's actions were generally antihyperalgesic and antiallodynic, rather than analgesic, in that the responsiveness of the control (sham-operated) hindpaw was unaffected. We conclude that felbamate suppresses neuropathic pain sensations and that its effectiveness may be due to multiple mechanisms of action. The recently discovered severe side-effect liability of felbamate is likely to preclude its clinical application.