Tramadol and several anticonvulsants synergize in attenuating nerve injury-induced allodynia

Abstract

Neuropathic pain results from injury or dysfunction of the central or peripheral nervous system. The treatment of neuropathic pain is challenging, in part because of its multiple etiologies. The present study explores combinations of the analgesic tramadol and each of four anticonvulsants in the treatment of surgically induced (ligation of the L5 spinal nerve) allodynia in rats. Each of the five drugs studied exhibited a dose-dependent antiallodynic effect. When studied in combination, tramadol and each of two of the anticonvulsants (topiramate and RWJ-333369) interacted synergistically at all three ratios studied, whereas tramadol and each of the other two anticonvulsants (gabapentin and lamotrigine) exhibited a synergistic antiallodynic effect at only one of three ratios investigated. In addition, tramadol and topiramate were found to interact synergistically in a nociceptive pain model, the mouse hot-plate test. These studies suggest the benefit of using combinations of analgesics and anticonvulsants in the relief of neuropathic pain.