Gabapentin enhances the analgesic response to morphine in acute model of pain in male rats

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Whenever opioids as drug of choice result in inadequate analgesia, the combinational therapy would be the solution. In this study the co-administration of gabapentin with morphine is evaluated in acute model of pain. Therefore the antinociceptive effect of gabapentin (30 or 90mg/kg, s.c.) and morphine (0.5, 1 or 3mg/kg, s.c.) alone or in combination were measured by tail-flick test in intact adult male rats. Control rats received normal saline. Tail-flick latency time and Area Under Curve (AUC), as antinociception index were calculated for each group. There was not any significant difference between the antinociceptive response of 0.5mg/kg morphine and 30mg/kg gabapentin as compared to controls, but co-administration of these subanalgesic doses increased significantly AUC as compared to morphine alone. The co-administration of gabapentin with analgesic doses of 1 and 3mg/kg morphine had also increased significantly AUC. Therefore, gabapentin enhanced the antinociceptive effect of both analgesic and subanalgesic doses of morphine in a dose dependent manner. In conclusion co-administration of gabapentin with low doses of morphine produced therapeutic analgesia which could have important clinical application. © 2006 Elsevier Inc. All rights reserved.