The analgesic effect of the methanolic extract of Acanthus montanus.

The analgesic effect of the methanolic leaf extract of Acanthus montanus was studied in rats using the cold water tail flick assay, and in mice using the tail immersion, tail clip, acetic acid induced writhing and formalin pain tests. The results showed dose-dependent and significant (P<0.05) increases in pain threshold, at 60 min post treatment, with doses of 200 and 400 mg/kg of the extract in tail flick, tail immersion and tail clip methods. The effects of the extract were significantly (P<0.05) lower than those produced by morphine (10 mg/kg) in the same tests. The extract (100-400 mg/kg) exhibited a dose-dependent inhibition of writhing and also showed a significant (P<0.001) inhibition of both phases of the formalin pain test, but with a less intense effect on the first than on the second phase. The results indicate that the analgesic effect of Acanthus montanus methanolic extract is both centrally and peripherally mediated.