The antinociceptive effects of systemic administration of tramadol, gabapentin and their combination on mice model of acute pain.

Objectives: The aim of the present study was to investigate the possible antinociceptive effects of systemic administration of tramadol and gabapentin either alone or in combination on acute pain models in mice.

Methods: After obtaining the approval of Animal Ethics Committee; 96 BALB/c albino male mice were divided into 12 groups: (I) control without injection, (II) control treated with saline, (III)-(IV) mice treated with tramadol 10 mg/kg or 30 mg/kg, (V)-(VIII) mice treated with gabapentin; 30, 100, 200, 300 mg/kg respectively. In order to determine possible interactions between tramadol gabapentin and; mice received four different combinations of tramadol + gabapentin (30+30, 30+100, 30+200 and 30+300 mg/kg) (Groups IX-XII respectively). Mice received 0.1 ml solution for every 10 g of their weight. The drug was injected into peritonea. Thirty minutes after the drug injection, tail-flick and hot-plate tests were conducted.

Results: Ten and 30 mg/kg tramadol produced dose dependent antinociceptive effect in tail-flick and hot plate tests. Gabapentin had no antinociceptive effect in the tail flick test except 300 mg/kg dose, and had dose dependent antinociceptive effect in hot-plate test. In both tests, various combinations of tramadol and gabapentin produced an antinociceptive effect that is greater than that produced by tramadol and gabapentin alone. But, just 30 mg/kg tramadol + 300 mg/kg gabapentin combination caused statistically significant increase in both tests (p<0.05).

Conclusion: When gabapentin and tramadol were used in combination, gabapentin had no additive antinociceptive effect except for 300 mg/kg in tail-flick and hot-plate tests. Tail-flick test showed that tramadol produced better antinociceptive effect than gabapentin.