Modulatory Role of Morphine and Gabapentin as Anti-inflammatory Agents Alone and on Co- administration with Diclofenac in Rat Paw Edema

Objective: To evaluate the antiinflammatory effects of Morphine and Gabapentin alone and as adjuvant with diclofenac by using formalin induced paw edema model. Methods: After acclimatization of one week, adult Sprague-Dawley rats were divided into two groups: control and treatment (n=6). Treatment group received diclofenac (10 mg/kg), gabapentin (150 mg/kg), morphine (15 mg/kg), gabapentin (150 mg/kg) + diclofenac (10 mg/kg) and morphine (15 mg/kg) + diclofenac (10 mg/kg), respectively. Paw edema was produced by injecting 0.2ml of 2% formalin subcutaneously on the dorsal surface of right hind paw. Animals received drug treatment 30 minutes before injection of formalin and paw volume was measured at 0, 30, 60, 120 and 240 minutes after formalin challenge with help of mercury plethysmometer. Results: Both morphine and gabapentin alone and in combination with diclofenac caused a significant reduction (p< 0.01) in rat paw edema when compared to group given saline only. Reduction in paw edema with gabapentin and diclofenac was significantly superior when compared with either drug alone. Conclusions: Combination of gabapentin and diclofenac showed synergistic anti-inflammatory effect as compared to either drug alone or combination of morphine + diclofenac groups.