The Effects of Chronic Gabapentin Administration on the Inflammatory Response in Rats

Besides its approval as an adjunctive anticonvulsant, gabapentin was reported to be effective in neuropathic and inflammatory pain. Antihyperalgesic effect of gabapentin may be related to possible antiinflammatory activity. We aimed to examine the antiinflammatory effect of chronic gabapentin administration on inflammatory response in rats. Experiments were performed with the permission of the Local Ethical Committee of Eskisehir Osmangazi University for the Animal Experimentation (03.03.2011/192). Male Spraque-Dawley rats (200-250g) were randomly divided into control (saline), gabapentin 10, 30, 100mg/kg and diclofenac 5mg/kg groups (n: 8 in each group). 0.1ml of 2% formalin solution was injected to the plantar region of the left paw of each rat, on the 1st and 3rd days of the experimental procedure. Drug or saline treatments were started one day after (4th day) the last formalin injection, administered via gavage for 10 days. Paw thickness of the left hind paw was measured on the 1st day before formalin injection, on the 4th day before the beginning of drug or saline treatments, on the 14th day (one day after the treatment procedure) with a micrometer. The percent edema and edema inhibition was calculated. Results were statistically analysed with Kruskal-Wallis test. All doses of gabapentin and diclofenac decreased %paw-edema and increased %edema inhibition compared to control group (p<0.05). 30 and 100mg/kg gabapentin decreased % paw-edema and increased % edema inhibition compared to diclofenac (p<0.05) more effectively. We suggest that chronically administered gabapentin may possess antiinflammatory effect which was more than the effect of the reference antiinflammatory drug, diclofenac.