Antinociceptive evaluation of anticonvulsant gabapentin with a conventional nonopioid analgesic in phasic and tonic animal model of acute and chronic pain

Background: Some antiepileptic drugs have been shown to be clinically efficacious in treatment of neuropathic pain and are being used by clinician. Methods: This study determined the analgesic effect of gabapentin in rats in biphasic animal pain model of acute and chronic inflammatory pain and compared its potency with a conventional nonopioid analgesic diclofenac. Results: Per oral administration of gabapentin produced no any marked effect on early phase response of formalin test, but significantly suppressed the late phase response, while diclofenac produced significant anti-nociceptive effect in both phases of formalin test. Conclusion: Thus, we have observed that gabapentin produced antinociception in second phase of formalin test, which reflects chronic inflammatory pain.