title: Comparison of antinociceptive effect of the antiepileptic drug gabapentin to that of various dosage combinations of gabapentin with lamotrigine and topiramate in mice and rats.
abstract: BACKGROUND
  Newer anticonvulsants have a neuromodulatory effect on pain perception mechanisms in a hyperexcitable and damaged nervous system.
  
  
  OBJECTIVE
  This study was designed to study the analgesic effects of gabapentin alone and in combination with lamotrigine and topiramate in experimental pain models.
  
  
  METHODS
  Adult albino mice (n=490) weighing 20-30 g and rats (n=130) weighing 100-200 g were injected intraperitoneally with gabapentin, lamotrigine, and topiramate alone and in different dose combinations. The hot-plate method, tail-flick method, capsaicin-induced mechanical hyperalgesia, and formalin assay were used to assess the antinociceptive effects.
  
  
  RESULTS
  Of the three antiepileptic drugs, when given separately, gabapentin was more efficacious than either topiramate or lamotrigine in all the pain models. Combination of 25 mg/kg gabapentin with 25 mg/kg topiramate was more efficacious (P<.05) than 50 mg/kg gabapentin alone in the capsaicin-induced mechanical hyperalgesia test. Similarly, 50 mg/kg gabapentin with 50 mg/kg topiramate or 5 mg/kg lamotrigine was more efficacious (P<.05) than 50 or 100 mg/kg gabapentin alone in late-phase formalin-induced behaviors.
  
  
  CONCLUSIONS
  Combination of gabapentin with either lamotrigine or topiramate produced better results than gabapentin alone in capsaicin-induced mechanical hyperalgesia test and in late-phase formalin-induced behaviors.
authors: Department of Pharmacology, Kathmandu Medical College and Teaching Hospital, Kathmandu, Nepal.
authors: Keshab Raj
authors: KR
authors: Paudel
authors: Sk
authors: S
authors: Bhattacharya
authors: Gp
authors: G
authors: Rauniar
authors: Bp
authors: B
authors: Das