Abstract

The analgesic effect of the ethanolic whole plant extract of Sida acuta L. (Asteraceae) 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 < 0.001) increases in pain threshold at 60 min post-treatment with doses of 100, 200, and 300 mg/kg of the extract in tail flick, tail immersion, and tail clip tests. The effects of the extract were significantly (P < 0.001) lower than those produced by morphine (10 mg/kg) in the same tests. The extract (100, 200, and 300 mg/kg) exhibited a dose-dependent inhibition of writhing and also showed a significant (P < 0.001) inhibition in both phases of the formalin pain test, but with a less intense effect in the first phase. The results indicate that the analgesic effect of S.acuta ethanolic extract is both centrally and peripherally mediated which confirms the traditional claims of plant in ayurveda.